\input texinfo @c -*-texinfo-*- @c %**start of header (This is for running Texinfo on a region.) @setfilename groff @settitle The GNU Troff Manual @setchapternewpage odd @footnotestyle separate @c %**end of header (This is for running Texinfo on a region.) @dircategory Miscellaneous @direntry * Groff: (groff). The GNU troff document formatting system. @end direntry @smallbook @iftex @finalout @end iftex @ifinfo This Info file documents GNU troff version 1.12. Published by the Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA Copyright (C) 1994, 1999 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. @ignore Permission is granted to process this file through TeX and print the results, provided the printed document carries copying permission notice identical to this one except for the removal of this paragraph (this paragraph not being relevant to the printed manual). @end ignore Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled ``GNU General Public License'' is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled ``GNU General Public License'' may be included in a translation approved by the Free Software Foundation instead of in the original English. @end ifinfo @titlepage @title groff @subtitle The GNU implementation of @code{groff} @subtitle Edition 1.12 @subtitle October 1999 @author by Trent A.@w{ }Fisher @author and the maintainer of groff @c Include the Distribution inside the titlepage environment so @c that headings are turned off. Headings on and off do not work. @page @vskip 0pt plus 1filll Copyright @copyright{} 1994, 1999 Free Software Foundation, Inc. @sp 2 Version 1.13 of @code{groff}, @* October 1999 @sp 2 Published by the Free Software Foundation @* 59 Temple Place, Suite 330 @* Boston, MA 02111-1307 USA Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled ``GNU General Public License'' is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled ``GNU General Public License'' may be included in a translation approved by the Free Software Foundation instead of in the original English. Cover art by Etienne Suvasa. @end titlepage @page @node Top, Copying, (dir), (dir) @ifinfo This Info file documents groff version 1.13, the GNU implementation of the troff typesetting system. This is an in-progress document; contributions, comments, or contributions are welcome. Send them to bug-groff@@gnu.org. @end ifinfo @menu * Copying:: * Introduction:: * Invoking groff:: * Tutorial for Macro Users:: * -man:: * -ms:: * -me:: * -mm:: * Programming Tutorial:: * geqn:: * gtbl:: * gpic:: * grap:: * grefer:: * gsoelim:: * Devices:: * File formats:: * Installation:: * Request Index:: * Register Index:: * String Index:: * Macro Index:: * Program Index:: * Concept Index:: @end menu @node Copying, Introduction, Top, Top @cindex copying @unnumbered GNU GENERAL PUBLIC LICENSE @center Version 2, June 1991 @display Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. @end display @unnumberedsec Preamble The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software -- to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too. When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things. To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it. For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights. We protect your rights with two steps: (1)@w{ }copyright the software, and (2)@w{ }offer you this license which gives you legal permission to copy, distribute and/or modify the software. Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations. Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all. The precise terms and conditions for copying, distribution and modification follow. @iftex @unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION @end iftex @ifinfo @center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION @end ifinfo @enumerate 0 @item This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The ``Program'', below, refers to any such program or work, and a ``work based on the Program'' means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term ``modification''.) Each licensee is addressed as ``you''. Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does. @item You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program. You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee. @item You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section@w{ }1 above, provided that you also meet all of these conditions: @enumerate a @item You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change. @item You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License. @item If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.) @end enumerate These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it. 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In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License. @item You may copy and distribute the Program (or a work based on it, under Section@w{ }2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following: @enumerate a @item Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or, @item Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or, @item Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.) @end enumerate The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable. If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code. @item You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance. @item You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. 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This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License. @item If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License. @item The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and ``any later version'', you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation. @item If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally. @iftex @heading NO WARRANTY @end iftex @ifinfo @center NO WARRANTY @end ifinfo @item BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW@. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE@. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU@. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION. @item IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. @end enumerate @iftex @heading END OF TERMS AND CONDITIONS @end iftex @ifinfo @center END OF TERMS AND CONDITIONS @end ifinfo @page @unnumberedsec How to Apply These Terms to Your New Programs If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms. To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the ``copyright'' line and a pointer to where the full notice is found. @smallexample @var{one line to give the program's name and an idea of what it does.} Copyright (C) 19@var{yy} @var{name of author} This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE@. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA. @end smallexample Also add information on how to contact you by electronic and paper mail. If the program is interactive, make it output a short notice like this when it starts in an interactive mode: @smallexample Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author} Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details. @end smallexample The hypothetical commands @samp{show w} and @samp{show c} should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than @samp{show w} and @samp{show c}; they could even be mouse-clicks or menu items---whatever suits your program. You should also get your employer (if you work as a programmer) or your school, if any, to sign a ``copyright disclaimer'' for the program, if necessary. Here is a sample; alter the names: @smallexample @group Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. @var{signature of Ty Coon}, 1 April 1989 Ty Coon, President of Vice @end group @end smallexample This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License. @node Introduction, Invoking groff, Copying, Top @chapter Introduction @cindex introduction GNU @code{troff} (or @code{groff}) is a system for typesetting documents. @code{troff} is very flexible and has been in existence (and use) for about 3@w{ }decades. It is quite widespread and firmly entrenched in the @sc{Unix} community. @menu * What Is groff?:: * History:: * groff Capabilities:: * Macro Packages:: * Preprocessors:: * Postprocessors:: * Credits:: @end menu @node What Is groff?, History, Introduction, Introduction @section What Is @code{groff}? @cindex what is @code{groff}? @cindex @code{groff} -- what is it? @code{groff} is of an older generation of document preparation systems, which operate more like compilers than the more recent interactive WYSIWYG @footnote{What You See Is What You Get} systems. @code{groff} and its contemporary counterpart, @TeX{}, both work using a @dfn{batch} paradigm: The input (or @dfn{source}) files are normal text files with embedded formatting commands. These files can then be processed by @code{groff} to produce a typeset document on a variety of devices. Likewise, @code{groff} should not be confused with a @dfn{word processor}, since that term connotes an integrated system which includes an editor and a text formatter. Also, many word processors follow the WYSIWYG paradigm which was discussed earlier. Although WYSIWYG systems may be easier to use, they have a number of disadvantages compared to @code{troff}: @itemize @bullet{} @item They must be used on a bitmapped display to do any operations on your document. @item Most of the WYSIWYG systems are either non-free or are not very portable. @item @code{troff} is firmly entrenched in all @sc{Unix} systems. @item It is difficult to have a wide range of capabilities available within the confines of a GUI/window system. @item It is more difficult to make global changes to a document. @end itemize @quotation ``GUIs normally make it simple to accomplish simple actions and impossible to accomplish complex actions.'' --Doug Gwyn (22/Jun/91 in @code{comp.unix.wizards}) @end quotation @node History, groff Capabilities, What Is groff?, Introduction @section History @cindex history @code{troff} can trace its origins back to a formatting program called @code{runoff} which ran on MIT's CTSS system. This name came from the common phrase of the time ``I'll run off a document.'' The first version of @sc{Unix} was developed on a PDP-7 which was sitting around Bell Labs. In 1971 the developers wanted to get a PDP-11 for further work on the operating system. In order to justify the cost for this system, they proposed that they would implement a document formatting system for the AT&T patents division. This first formatting program was a reimplementation of @code{runoff}. In accordance with @sc{Unix}'s penchant for abreviations, it was named @code{roff} (an abreviation of @code{runoff}). When they needed a more flexible language, a new version of @code{roff} called @code{nroff} (Newer @code{roff}) was written. It had a much more complicated syntax, but provided the basis for all future versions. When they got a Graphic Systems CAT Phototypesetter, J.@w{ }F.@w{ }Ossanna wrote a version of @code{nroff} which would drive it. It was dubbed @code{troff} for typesetter @code{roff}, although many people have speculated that it actually means Times @code{roff} because of @code{troff}'s use of the Times font family by default. As such, the name @code{troff} is pronounced t-roff rather than trough. With @code{troff} came @code{nroff} (they were actually the same program except for some @samp{#ifdefs}), which was for producing output for line printers and ascii terminals. It understood everything @code{troff} did, and ignored the commands which were not aplicable (i.e.@: font changes). Since there are several things which cannot be done easily in @code{troff}, work on several preprocessors began. These programs would transform certain parts of a document into @code{troff}, which made a very natural use of pipes in @sc{Unix}. The @code{eqn} preprocessor allowed mathematical formul@ae{} to be specified in a much simpler and more intuitive manner. @code{tbl} is a preprocessor for formatting tables. The @code{refer} preprocessor (and the similar program, @code{bib}) processes citations in a document according to a bibliographic database. Unfortunately, Ossanna's @code{troff} was written in PDP-11 assembly language and produced output specifically for the CAT phototypesetter. He rewrote it in C, although it was now 7000@w{ }lines of uncommented code and still dependent on the CAT. As the CAT became less common, and was no longer supported by the manufacturer, the need to make it support other devices became a priority. However, before this could be done, he was killed in an auto accident. @pindex ditroff So, Brian Kernighan took on the task of rewriting @code{troff}. The newly rewritten version produced a device independent code which was very easy for postprocessors to read and translate to the appropriate printer codes. Also, this new version of @code{troff} (called @code{ditroff}) had several extentions, which included drawing functions. Due to the additional abilities of the new version of @code{troff}, several new preprocessors appeared. The @code{pic} preprocessor provides a wide range of drawing functions. Likewise the @code{ideal} preprocessor did the same, although via a much different paradigm. The @code{grap} preprocessor took specifications for graphs, but, unlike other preprocessors, produced @code{pic} code. James Clark began work on a GNU implementation of @code{ditroff} in early@w{ }1989. The first version, @code{groff}@w{ }0.3.1, was released June@w{ }1990. @code{groff} included @itemize @bullet{} @item A replacement for @code{ditroff} with many extentions. @item The @code{soelim}, @code{pic}, @code{tbl}, and @code{eqn} preprocessors. @item Postprocessors for ascii devices, PostScript, @TeX{} DVI, and X@w{ }windows. GNU @code{troff} also eliminated the need for a separate @code{nroff} program with a postprocessor which would produce ascii output. @item A version of the @code{-me} macros and an implementation of the @code{-man} macros. @end itemize Also, a front-end was included which could construct the, sometimes painfully long, pipelines required for all the post- and preprocessors. Development of GNU @code{troff} progressed rapidly, and saw the additions of a replacement for @code{refer}, an implementation of the @code{-ms} and @code{-mm} macros, and a program to deduce how to format a document (@code{grog}). It was declared a stable (i.e.@: non beta) package with the release of version@w{ }1.04 around November@w{ }1991. @node groff Capabilities, Macro Packages, History, Introduction @section @code{groff} Capabilities @cindex @code{groff} capabilities @cindex capabilities of @code{groff} So what exactly is @code{groff} capable of doing? @code{groff} provides a wide range of low-level text formatting operations. Using these, you can perform a wide range of formatting tasks, such as footnotes, table of contents, multiple columns, etc. @itemize @bullet{} @item Text filling, adjusting, and centering @item Hyphenation @item Page control @item Font and character size control @item Vertical spacing (i.e.@: double spacing) @item Line length and indenting @item Macros, strings, diversions, and traps @item Number registers @item Tabs, leaders, and fields @item Input and output conventions and character translation @item Overstrike, bracket, line drawing, and zero-width functions @item Local horizontal and vertical motions and the width function @item Three-part titles @item Output line numbering @item Conditional acceptance of input @item Environment switching @item Insertions from the standard input @item Input/output file switching @item Output and error messages @end itemize @node Macro Packages, Preprocessors, groff Capabilities, Introduction @section Macro Packages @cindex macro packages Since @code{groff} provides such low level facilities, it can be quite difficult to use by itself. However, @code{groff} provides a @dfn{macro} facility which allows you to specify how certain routine operations (e.g.@w{ }starting paragraphs, printing headers and footers, etc.)@: should be done. These macros can be collected together into a @dfn{macro package}. There are a number of macro packages available; the most common (and the ones described in this manual) are @code{-man}, @code{-me}, @code{-ms}, and @code{-mm}. @node Preprocessors, Postprocessors, Macro Packages, Introduction @section Preprocessors @cindex preprocessors Although @code{groff} provides most functions needed to format a document, some operations would be unwieldy (i.e.@: drawing pictures). Therefore, programs called preprocessors were written which understand their own language and produce the necessary groff operations. These preprocessors are able to differentiate their own input from the rest of the document via markers. To use a preprocessor, @sc{Unix} pipes are used to feed the output from the preprocessor into @code{groff}. Any number of preprocessors may be used on a given document; in this case, the preprocessors are linked together into one pipeline. However, in @code{groff}, the user does not need to construct the pipe, but only tell @code{groff} what preprocessors to use. @code{groff} currently has preprocessors for producing tables (@code{tbl}), typesetting equations (@code{eqn}), drawing pictures (@code{pic}), and for processing bibliographies (@code{refer}). An associated program which is useful when dealing with preprocessors is @code{soelim}. There are other preprocessors in existence, but there are, unfortunately, no free implementations available. They are for drawing pictures (@code{ideal} and @code{gremlin}), for drawing graphs (@code{grap}), and chemical structures (@code{chem}). @node Postprocessors, Credits, Preprocessors, Introduction @section Postprocessors @cindex postprocessors @code{groff} actually produces device independent code which may be fed into a postprocessor which will produce output for a particular device. Currently, @code{groff} has postprocessors for PostScript, ascii terminals, X@w{ }windows (for previewing), @TeX{} DVI format, and HTML. @node Credits, , Postprocessors, Introduction @section Credits @cindex credits Large portions of this manual were taken from existing documents, most notably, the manual pages for the @code{groff} package by James Clark, and Eric Allman's papers on the @code{-me} macro package. @node Invoking groff, Tutorial for Macro Users, Introduction, Top @chapter Invoking @code{groff} @cindex invoking @code{groff} @cindex @code{groff} invocation @pindex groff @pindex gtroff This section focuses on how to invoke the @code{groff} front end. This front end takes care of the details of constructing the pipeline among the preprocessors, @code{gtroff} and the postprocessor. It has become a tradition that GNU programs get the prefix @dfn{g} to distinguish it from its original counterparts provided by the host (@pxref{Environment}, for more details). Thus, for example, @code{geqn} is GNU @code{eqn}. On operating systems like Linux or the Hurd, which don't contain proprietary software, this prefix is omitted since GNU @code{troff} is the only used incarnation of @code{troff}. Exception: @code{groff} is never replaced by `roff'. @menu * Options:: * Environment:: * Invocation Examples:: @end menu @node Options, Environment, Invoking groff, Invoking groff @section Options @cindex options @pindex groff @pindex gtroff @pindex gpic @pindex geqn @pindex gtbl @pindex grefer @pindex gsoelim @code{groff} is a front-end to the groff document formatting system. Normally it runs the @code{gtroff} program and a postprocessor appropriate for the selected device. The default device is @samp{ps}. It can optionally preprocess with any of @code{gpic}, @code{geqn}, @code{gtbl}, @code{grefer}, or @code{gsoelim}. This section only documents options to the @code{groff} front end. Many of the arguments to @code{groff} are passed on to @code{gtroff}, therefore those are also included. Arguments to pre- or postprocessors can be found in @ref{Invoking gpic}, @ref{Invoking geqn}, @ref{Invoking gtbl}, @ref{Invoking grefer}, @ref{Invoking gsoelim}, @ref{Invoking grotty}, @ref{Invoking grops}, @ref{Invoking grohtml}, @ref{Invoking grodvi}, and @ref{Invoking gxditview} The command line format for @code{groff} is: @example groff [ -abehilpstvzCENRSVXZ ] [ -F@var{dir} ] [ -m@var{name} ] [ -T@var{def} ] [ -f@var{fam} ] [ -w@var{name} ] [ -W@var{name} ] [ -M@var{dir} ] [ -d@var{cs} ] [ -r@var{cn} ] [ -n@var{num} ] [ -o@var{list} ] [ -P@var{arg} ] [ -L@var{arg} ] [ @var{files}@dots{} ] @end example The command line format for @code{gtroff} is as follows. As you can see, many of the options to @code{groff} are actually passed on to @code{gtroff}. @example gtroff [ -abivzCER ] [ -w@var{name} ] [ -W@var{name} ] [ -d@var{cs} ] [ -f@var{fam} ] [ -m@var{name} ] [ -n@var{num} ] [ -o@var{list} ] [ -r@var{cn} ] [ -T@var{name} ] [ -F@var{dir} ] [ -M@var{dir} ] [ @var{files}@dots{} ] @end example Options without an argument can be grouped behind a single @samp{-}. A filename of @samp{-} denotes the standard input. @pindex grog The @code{grog} command can be used to guess the correct @code{groff} command to use to format a file. @table @samp @item -h Print a help message. @item -e Preprocess with @code{geqn}. @item -t Preprocess with @code{gtbl}. @item -p Preprocess with @code{gpic}. @item -s Preprocess with @code{gsoelim}. @item -R Preprocess with @code{grefer}. No mechanism is provided for passing arguments to @code{grefer} because most @code{grefer} options have equivalent commands which can be included in the file. @xref{grefer}, for more details. @pindex troffrc Note that @code{gtroff} also accepts a @samp{-R} option, which is not accessible via @code{groff}. This option prevents the loading of the @file{troffrc} file. @item -v Make programs run by @code{groff} print out their version number. @item -V Print the pipeline on stdout instead of executing it. @item -z Suppress output from @code{gtroff}. Only error messages will be printed. @item -Z Do not postprocess the output of @code{gtroff}. Normally @code{groff} will automatically run the appropriate postprocessor. @item -P@var{arg} Pass @var{arg} to the postprocessor. Each argument should be passed with a separate @samp{-P} option. Note that groff does not prepend @samp{-} to @var{arg} before passing it to the postprocessor. @item -l Send the output to a printer. The command used for this is specified by the print command in the device description file. @item -L@var{arg} Pass @var{arg} to the spooler. Each argument should be passed with a separate @samp{-L} option. Note that @code{groff} does not prepend a @samp{-} to @var{arg} before passing it to the postprocessor. @item -T@var{dev} Prepare output for device @var{dev}. The default device is @samp{ps}. The following are the output devices currently available: @table @samp @item ps For PostScript printers and previewers. @item dvi For TeX dvi format. @item X75 For a 75 dpi X11 previewer. @item X100 For a 100dpi X11 previewer. @item ascii For typewriter-like devices. @item latin1 For typewriter-like devices using the ISO Latin-1 character set. @item lj4 For an HP LaserJet4-compatible (or other PCL5-compatible) printer. @item html To produce HTML output. @end table The postprocessor to be used for a device is specified by the @code{postpro} command in the device description file. (@xref{Font Files}, for more info.) This can be overridden with the @samp{-X} option. @item -X Preview with @code{gxditview} instead of using the usual postprocessor. This is unlikely to produce good results except with @samp{-Tps}. @item -N Don't allow newlines with @code{eqn} delimiters. This is the same as the @samp{-N} option in @code{geqn}. @item -S Safer mode. Pass the @samp{-S} option to @code{gpic} and use the @samp{-msafer} macros with @code{gtroff}. @item -a Generate an ASCII approximation of the typeset output. @item -b Print a backtrace with each warning or error message. This backtrace should help track down the cause of the error. The line numbers given in the backtrace may not always be correct: @code{troff}'s idea of line numbers gets confused by @code{as} or @code{am} requests. @item -i Read the standard input after all the named input files have been processed. @item -w@var{name} Enable warning @var{name}. Available warnings are described in @ref{Debugging}. Multiple @samp{-w} options are allowed. @item -W@var{name} Inhibit warning @var{name}. Multiple @samp{-W} options are allowed. @item -E Inhibit all error messages. @item -C Enable compatibility mode. @item -d@var{cs} @itemx -d@var{name}=s Define @var{c} or @var{name} to be a string @var{s}; @var{c} must be a one-letter @var{name}. @item -f@var{fam} Use @var{fam} as the default font family. @item -m@var{name} Read in the file @file{tmac.@var{name}}. Normally this will be searched for in @code{groff}'s lib directory. @item -n@var{num} Number the first page @var{num}. @item -o@var{list} Output only pages in @var{list}, which is a comma-separated list of page ranges; @var{n} means print page @var{n}, @samp{@var{m}-@var{n}} means print every page between @var{m} and @var{n}, @samp{-@var{n}} means print every page up to @var{n}, @samp{@var{n}-} means print every page from @var{n}. @code{troff} will exit after printing the last page in the list. @item -r@var{cn} @itemx -r@var{name}=@var{n} Set number register @var{c} or @var{name} to @var{n}; @var{c} must be a one-letter @var{name}; @var{n} can be any troff numeric expression. @item -F@var{dir} Search @var{dir} for subdirectories dev@var{name} (@var{name} is the name of the device) for the @file{DESC} file and font files before the normal directory. @item -M@var{dir} Search directory @var{dir} for macro files before the normal directory. @end table @node Environment, Invocation Examples, Options, Invoking groff @section Environment @cindex environment There are also several environment variables which can modify groff's behavior. @table @code @item GROFF_COMMAND_PREFIX If this is set to @var{X}, then @code{groff} will run @var{X}@code{troff} instead of @code{gtroff}. This also applies to @code{tbl}, @code{pic}, @code{eqn}, @code{refer}, and @code{soelim}. It does not apply to @code{grops}, @code{grodvi}, @code{grotty}, @code{grohtml}, @code{grolj4}, and @code{gxditview}. @item GROFF_TMAC_PATH A colon separated list of directories in which to search for macro files. @item GROFF_TYPESETTER Default device. @item GROFF_FONT_PATH A colon separated list of directories in which to search for the @code{dev}@var{name} directory. @item PATH The search path for commands executed by groff. @item GROFF_TMPDIR The directory in which temporary files will be created. If this is not set and @code{TMPDIR} is set, temporary files will be created in that directory. Otherwise temporary files will be created in @code{/tmp}. The @code{grops} and @code{grefer} commands can create temporary files. @end table @node Invocation Examples, , Environment, Invoking groff @section Invocation Examples @cindex invocation examples @cindex examples of invocation This section will list several common uses of @code{groff} and the command line which will accomplish it. @example groff file groff -X -me file groff -mm -rD1 -z file groff -tps -me file | lpr -Plw2 ... any more?? ... @end example @subsection @code{grog} @code{grog} reads files and guesses which of the @code{groff} preprocessors and/or macro packages are are required for formatting them, and prints the @code{groff} command including those options on the standard output. The options generated are one of @samp{-e}, @samp{-man}, @samp{-me}, @samp{-mm}, @samp{-ms}, @samp{-p}, @samp{-s}, and @samp{-t}. A filename of @samp{-} is taken to refer to the standard input. If no files are specified the standard input will be read. Any specified options will be included in the printed command. No space is allowed between options and their arguments. For example, @example grog -Tdvi paper.ms @end example will guess the approriate command to print @file{paper.ms} and then run it after adding the @samp{-Tdvi} option. @node Tutorial for Macro Users, -man, Invoking groff, Top @chapter Tutorial for Macro Users @cindex tutorial for macro users @cindex macro tutorial for users @cindex user's tutorial for macros @cindex user's macro tutorial Most users tend to use a macro package to format their papers. This means that the whole breadth of @code{groff} is not neccessary for most people. This chapter covers the material needed to efficiently use a macro package. @menu * Basics:: * Common Features:: @end menu @node Basics, Common Features, Tutorial for Macro Users, Tutorial for Macro Users @section Basics @cindex basics This section covers some of the basic concepts you will need to understand to use a macro package.@footnote{This section is derived from @cite{Writing Papers with nroff using -me} by Eric P.@w{ }Allman} References are made throughout to more detailed information, if desired. @code{groff} reads an input file prepared by the user and outputs a formatted paper suitable for publication or framing. The input consists of text, or words to be printed, and embedded commands (@dfn{requests} and @dfn{escapes}), which tell @code{groff} how to format the printed copy. For more detail on this @pxref{Embedded Commands}. The word @dfn{argument} is used in this manual to mean a word or number which appears on the same line as a request which modifies the meaning of that request. For example, the request @example .sp @end example @noindent spaces one line, but @example .sp 4 @end example @noindent spaces four lines. The number@w{ }4 is an argument to the @code{sp} request which says to space four lines instead of one. Arguments are separated from the request and from each other by spaces. More details on this can be found in @ref{Request Arguments}. The primary function of @code{groff} is to collect words from input lines, fill output lines with those words, justify the right hand margin by inserting extra spaces in the line, and output the result. For example, the input: @example Now is the time for all good men to come to the aid of their party. Four score and seven years ago,... @end example @noindent will be read, packed onto output lines, and justified to produce: @quotation Now is the time for all good men to come to the aid of their party. Four score and seven years ago,... @end quotation @cindex break @cindex line break Sometimes you may want to start a new output line even though the line you are on is not yet full; for example, at the end of a paragraph. To do this you can cause a @dfn{break}, which starts a new output line. Some requests cause a break automatically, as do blank input lines and input lines beginning with a space. Not all input lines are text to be formatted. Some of the input lines are requests which describe how to format the text. Requests always have a period or an apostrophe (@samp{'}) as the first character of the input line. The text formatter also does more complex things, such as automatically numbering pages, skipping over page boundaries putting footnotes in the correct place, and so forth. Here a few hints for preparing text for input to @code{groff}. First, keep the input lines short. Short input lines are easier to edit, and @code{groff} will pack words onto longer lines for you anyhow. In keeping with this, it is helpful to begin a new line after every period, comma, or phrase, since common corrections are to add or delete sentences or phrases. Secondly, do not hyphenate words at the end of lines -- @code{groff} is smart enough to hyphenate words for you as needed, but is not smart enough to take hyphens out and join a word back together. Also, words such as ``mother-in-law'' should not be broken over a line, since then you will get a space where not wanted, such as ``mother- in-law''. @findex ls @cindex double spacing @cindex spacing Groff will double space output text automatically if you use the request @samp{.ls 2}. You can revert to single spaced mode by typing @samp{.ls 1}. A number of requests allow you to change the way the printed copy looks, sometimes called the @dfn{layout} of the output page. Most of these requests adjust the placing of @dfn{white space} (blank lines or spaces). @findex bp @cindex new page The @samp{.bp} request starts a new page. @findex sp @cindex blank lines @cindex empty lines The request @samp{.sp @var{N}} leaves @var{N} lines of blank space. @var{N} can be omitted (meaning skip a single line) or can be of the form @var{N}i (for @var{N} inches) or @var{N}c (for @var{N} centimeters). For example, the input: @example .sp 1.5i My thoughts on the subject .sp @end example @noindent leaves one and a half inches of space, followed by the line ``My thoughts on the subject'', followed by a single blank line. @findex ce @cindex centering lines Text lines can be centered by using the @samp{.ce} request. The line after @samp{.ce} is centered (horizontally) on the page. To center more than one line, use @samp{.ce @var{N}} (where @var{N} is the number of lines to center), followed by the @var{N} lines. If you want to center many lines but don't want to count them, type: @example .ce 1000 lines to center .ce 0 @end example @noindent The @samp{.ce 0} request tells @code{groff} to center zero more lines, in other words, stop centering. @findex br @cindex line break @cindex break All of these requests cause a break; that is, they always start a new line. If you want to start a new line without performing any other action, use @samp{.br}. @node Common Features, , Basics, Tutorial for Macro Users @section Common Features @cindex common features @cindex features, common Groff provides very low level operations for formatting a document. There are many common routine operations which are done in all documents. These common operations are written into @dfn{macros} and collected into a @dfn{macro package}. All macro packages provide certain common capabilities which fall into the following categories. @subsection Paragraphs @cindex paragraphs One of the most common and most used capability is starting a paragraph. There are a number of different types of paragraphs, any of which can be initiated with macros supplied by the macro package. Normally paragraphs start with a blank line and the first line indented, like the text in this manual. There are also block style paragraphs, which omit the indentation: @example Some men look at constitutions with sanctimonious reverence, and deem them like the ark of the covenant, too sacred to be touched. @end example And there are also indented paragraphs which begin with a tag or label at the margin and the remaining text indented. @example one This is the first paragraph. Notice how the first line of the resulting paragraph lines up with the other lines in the paragraph. longlabel This paragraph had a long label. The first character of text on the first line will not line up with the text on second and subsequent lines, although they will line up with each other. @end example A variation of this is a bulleted list.... @subsection Sections and Chapters Most macro packages supply some form of section headers. The simplest kind is simply the heading on a line by itself in bold type. Others supply automatically numbered section heading or different heading styles at different levels. Some, more sophisticated, macro packages supply macros for starting chapters and appendicies. @subsection Headers and Footers Every macro packages gives you some way to manipulate the headers and footers (or @dfn{titles} on each page. Some packages will allow you to have different ones on the even and odd pages (for material printed in a book form). The titles are called three-part titles, that is, there is a left-justified part, a centered part, and a right-justified part. An automatically generated page number may be put in any of these fields with the @samp{%} character. @subsection Page Layout Most macro packages let you specify top and bottom margins and other details about the appearance of the printed pages. @subsection Displays @cindex displays Displays are sections of text to be set off from the body of the paper. Major quotes, tables, and figures are types of displays, as are all the examples used in this document. @cindex quotes, major @cindex major quotes Major quotes are quotes which are several lines long, and hence are set in from the rest of the text without quote marks around them. @cindex list A list is an indented, single spaced, unfilled display. Lists should be used when the material to be printed should not be filled and justified like normal text, such as columns of figures or the examples used in this paper. @cindex keep A keep is a display of lines which are kept on a single page if possible. An example of where you would use a keep might be a diagram. Keeps differ from lists in that lists may be broken over a page boundary whereas keeps will not. @cindex keep, floating @cindex floating keep Floating keeps move relative to the text. Hence, they are good for things which will be referred to by name, such as ``See figure 3''. A floating keep will appear at the bottom of the current page if it will fit; otherwise, it will appear at the top of the next page. Meanwhile, the surrounding text will `flow' around the keep, thus leaving now blank areas. @subsection Footnotes and annotations @cindex footnotes @cindex annotations There are a number of requests to save text for later printing. Footnotes are printed at the bottom of the current page. Delayed text is intended to be a variant form of foot- note; the text is printed only when explicitly called for, such as at the end of each chapter. Delayed text is very similar to a footnote except that it is printed when called for explicitly. This allows a list of references to appear (for example) at the end of each chapter, as is the convention in some disciplines. Most macro packages which supply this functionality also supply a means of automatically numbering either type of annotation. @subsection Table of Contents Tables of contents are a type of delayed text having a tag (usually the page number) attached to each entry after a row of dots. The table accumulates throughought the paper until printed, usually after the paper has ended. Many macro packages will provide the abilitly to have several tables of contents (i.e. one standard one, one for tables, &c.) @subsection Indexes While some macro packages will use the term @dfn{index}, none actually provide that functionality. The facilities they call indexes are actually more appropriate for tables of contents. @subsection Paper formats Some macro packages provide stock formats for various kinds of documents. Many of them provide a common format for the title and opening pages of a technical paper. The -mm macros in particular provide formats for letters and memorandums. @subsection Multiple Columns Some macro packages (except -man) provide the ability to have two or more columns on a page. @subsection Font and Size changes The builtin font and size functions are not always intuitive, so all macro packages provide macros to make these operations simpler. @subsection Predefined Strings Most macro packages provide various predefined strings for a variety of uses, examples are sub- and super-scripts, printable dates, quotes and various special characters. @subsection Preprocessor Support All macro packages provide support for the various preprocessors. @subsection Configuration and Customization Some macro packages provide means of customizing many of details of how the package behaves. This ranges from setting the default type size to changing the appearance of section headers. @node -man, -ms, Tutorial for Macro Users, Top @chapter -man @cindex @code{-man} @node -ms, -me, -man, Top @chapter -ms @cindex @code{-ms} @node -me, -mm, -ms, Top @chapter -me @cindex @code{-me} @node -mm, Programming Tutorial, -me, Top @chapter -mm @cindex @code{-mm} @node Programming Tutorial, geqn, -mm, Top @chapter Programming Tutorial @cindex programming tutorial @cindex tutorial for programming This chapter covers @strong{all} of the facilities of groff. If you are intending to use a macro package, you probably do not want to read this chapter. @menu * Text:: * Input Conventions:: * Measurements:: * Expressions:: * Identifiers:: * Embedded Commands:: * Registers:: * Manipulating Filling and Adjusting:: * Manipulating Hyphenation:: * Manipulating Spacing:: * Tabs and Fields:: * Character Translations:: * Line Layout:: * Page Layout:: * Page Control:: * Fonts:: * Sizes:: * Strings:: * Conditionals and Loops:: * Writing Macros:: * Page Motions:: * Drawing Functions:: * Traps:: * Diversions:: * Environments:: * I/O:: * Postprocessor Access:: * Miscellany:: * Debugging:: * Implementation Differences:: * Summary:: @end menu @node Text, Input Conventions, Programming Tutorial, Programming Tutorial @section Text @cindex text @code{groff} input files contain text with control commands interspersed throughout. But, even without control codes, @code{groff} will still do several things with your text: filling and adjusting, adding additional space after sentences, hyphenating and inserting implicit line breaks. @menu * Filling and Adjusting:: * Hyphenation:: * Sentences:: * Tab Stops:: * Implicit Line Breaks:: @end menu @node Filling and Adjusting, Hyphenation, Text, Text @subsection Filling and Adjusting @cindex filling and adjusting @cindex adjusting and filling When troff reads in text it collects words from input and fits as many of them together on one output line as it can. This is known as @dfn{filling}. Once troff has a @dfn{filled} line it will try to @dfn{adjust} it. which means it will widen the spacing between words until the text reaches the right margin (in the default adjustment mode). Extra spaces between words are preserved, but spaces at the end of lines are ignored. Spaces at the front of a line will cause a @dfn{break} (breaks will be explained in @ref{Implicit Line Breaks}) @c distribute these through the text @xref{Manipulating Filling and Adjusting} @node Hyphenation, Sentences, Filling and Adjusting, Text @subsection Hyphenation @cindex hyphenation Since the odds of finding a set of words, for every output line, which will fit nicely on a line without inserting excessive amounts of space between words is not great, troff will hyphenate words so that lines can be justified without there being too much space between words. It uses an internal hyphenation algorithm, to indicate which words can be hyphenated and how to do so. When a word is hyphenated the first part of the word will be added to the current filled line being output (with an attached hyphen), and the other portion will be added to the next line to be filled. @c distribute these through the text @xref{Manipulating Hyphenation} @node Sentences, Tab Stops, Hyphenation, Text @subsection Sentences @cindex sentences Although it is often debated, some typesetting rules say there should be different amounts of space after various puctuation marks. For example, a period at the end of a sentence should have twice as much space following it as would a comma or a period as part of an abbreviation. @cindex sentence spaces @cindex spaces between sentences Troff does this by flagging certain characters (normally @samp{!}, @samp{?} and @samp{.}) as @dfn{end of sentence} characters. When troff encounters one of these characters at the end of a line it will append two @dfn{sentence spaces} in the formatted output. (thus, one of the conventions mentioned in @ref{Input Conventions}). @c also describe how characters like ) are treated here -jjc @c gotta do some research on this -trent @node Tab Stops, Implicit Line Breaks, Sentences, Text @subsection Tab Stops @cindex tab stops @cindex stops, tabulator Groff translates tabs in the input into movements to the next tab stop. These tab stops are initially located every half inch across the page. Using this you can make simple tables. However, this can often be deceptive as the appearance (and width) of your text on a terminal and the results from groff can vary greatly. Also, a possible sticking point is that lines beginning with tab characters will still be filled, again producing unexpected results. For example, the following input @example 1 2 3 4 5 @end example @noindent will produce @example 1 2 3 4 5 @end example @c Tab stops are with respect to the input line. -jjc @c did that last section address that?? -trent @c distribute these through the text @xref{Tabs and Fields} @node Implicit Line Breaks, , Tab Stops, Text @subsection Implicit Line Breaks @cindex implicit line breaks @cindex implicit breaks of lines @cindex line, implicit breaks @cindex break @cindex break, implicit @cindex line break An important concept in troff is the @dfn{break}. When a @dfn{break} occurs, troff will output the partially filled line (unadjusted), and resume collecting and filling text on the next output line. @cindex blank line @cindex empty line @cindex line, blank There are several ways to cause a break in troff. A blank line will not only cause a break, but it will also cause a one line vertical space (effectively a blank line) to be output. A line which begins with a space will cause a break and the space will be output at the beginning of the next line. Note that this space isn't adjusted, even in fill mode. The end of file will also cause a break (otherwise the last line of your document may vanish!) Certain @dfn{requests} also cause breaks, implicitly or explicity. This will be discussed later. @c distribute these through the text @xref{Manipulating Filling and Adjusting} @node Input Conventions, Measurements, Text, Programming Tutorial @section Input Conventions @cindex input conventions @cindex conventions for input Since groff does filling automatically, it is traditional in groff not to try and type things in as nicely formatted paragraphs. These are some conventions commonly used when typing groff text: @itemize @bullet{} @item Break lines after punctuation, particularily at the ends of sentences, and in other logical places. Keep separate phrases on lines by themselves, as entire phrases are often added or deleted when editing. @item Try to keep lines less than 40-60 characters, to allow space for inserting more text. @item Do not try to do any formatting in a WYSIWYG manner (i.e. don't try and use spaces to get proper indentation). @end itemize @node Measurements, Expressions, Input Conventions, Programming Tutorial @section Measurements @cindex measurements @cindex units of measurement @cindex basic units @cindex machine units Troff (like any other programs) requires numeric parameters to specify various measurements. Most numeric parameters @footnote{those that specify vertical or horizontal motion or a type size} may have a measurement unit attached. These units are specified as a single character which immediately follows the number or expression. Each of these units are understood, by troff, to be a multiple of its @dfn{basic unit}. So, whenever a different measurement unit is specified troff converts this into its basic units. This basic unit, represented by a @samp{u} is a device dependent measurement which is quite small, ranging from 1/75th to 1/72000th of an inch. Some of the measurement units are compleatly independent of any of the current settings (e.g. type size) of groff. @table @samp @item i @cindex inch Inches. An antiquated measurement unit still in use in certain backwards countries. @item c @cindex centimeter Centimeters. @item p @cindex points Points. This is a typesetter's measurement used for measure type size. It is 72 points to an inch. @item P @cindex pica Pica. Another typesetting measurement. 6 Picas to an inch. @item s @item z @end table The other measurements understood by troff are dependent on settings currently in effect in troff. These are very useful for specifying measurements which should look proper with any size of text. @table @samp @item m @cindex em Ems. This unit is equal to the current font size in points. So called because it is @emph{approximately} the width of the letter @samp{m} in the current font. @item n @cindex en Ens. This is half of an em. @item v @cindex vertical space @cindex space, vertical Vertical space. This is equivalent to the current line spacing. @xref{Sizes}, for more information about this. @item M 100ths of an em. @end table @c distribute these through the text @xref{Fractional Type Sizes} @menu * Default Units:: @end menu @node Default Units, , Measurements, Measurements @subsection Default Units @cindex default units @cindex units, default Many requests take a default unit. While this can be helpful at times, it can cause strange errors in some expressions. For example, the line length request expects em's. Here are several attempts to get 3.5 inches and the results: @example 3.5i @result{} 3.5i 7/2 @result{} 0i 7/2i @result{} 0i 7i/2 @result{} .1i 7i/2u @result{} 3.5i @end example As you can see, the safest way to specify measurements is to always attach a scaling indicator. @node Expressions, Identifiers, Measurements, Programming Tutorial @section Expressions @cindex expressions Troff has most of operators common to other languages: @itemize @bullet @item Arithmetic: +, -, /, *, % @item Comparison: <, >, >=, <=, =, == (the last two are the same) @item Logical: &, : @item Unary operators: -, +, ! (if/while only??) @item Maximum and minimum: >?, | in |<-- | -->| po |<-----------ll------------>| +----+----+----------------------+----+ | : : : | +----+----+----------------------+----+ @end group @end example These dimensions are: @ftable @code @item po @vindex .o @dfn{Page offset}--This is the leftmost postition of text on the final output. This can be adjusted with the @code{po} request, and the current setting can be found in the builtin number register @code{.o} Note, that this request does not cause a break, so changing the page offset in the middle of text being filled may not do what you expect. @item in @vindex .i @dfn{Indentation}--This is the distance from the left margin where text will be printed. This can be adjusted with the @code{in} request, and the current setting can be found in the builtin number register. @code{.i} This request causes a break. @findex ti @findex .in There is also the request @code{ti} which will cause one output line to be indented, after which the indentation returns to 0. This request causes a break. The number register @code{.in} is the indent that applies to the current output line. @item ll @findex .l @findex .ll @dfn{Line length}--This is the distance from the left margin to right margin. This can be adjusted with the @code{.ll} request, and the current setting can be found in the builtin number register @code{.l} Note, as the figure implies, line length is not affected by the current indentation. The number register @code{.ll} is the line length that applies to the current output line. @end ftable @example .in +.5i .ll -.5i A bunch of really boring text which should be indented from both margins. replace me with a better (and more) example! .in -.5i .ll +.5i @end example @node Page Layout, Page Control, Line Layout, Programming Tutorial @section Page Layout @cindex page layout @cindex layout, page Troff provides some very primitive operations for controlling page layout. @findex pl @vindex .p Troff lets you specify the @dfn{page length} via the @code{pl} request. This is the length of the physical output page. The current setting can be found in the builtin number register @code{.p}. Note that this only specifies the size of the page, not the not the top and bottom margins. Those are not done by groff directly, @xref{Traps}, for further information on how to do this. @cindex headers @cindex footers @cindex titles Troff provides several operations which help in setting up top and bottom titles (or headers and footers) @findex tl The @code{tl} request will print a @dfn{title line}, which consists of three parts: a left justified portion, a centered portion and a right justified portion. The argument to @code{tl} is specified as @code{'@var{left}'@var{center}'@var{right}'} The @samp{%} character is replaced with the current page number. @findex lt @vindex .lt The title line is printed using its own line length, which is specified with the @code{lt} request. The current setting of this is available in the @code{.lt} number register. @findex pn The @code{pn} request will change the page number of the @emph{next} page. The only argument is the page number. @vindex % @vindex .pn The current page number is stored in the number register @code{%}. The number register @code{.pn} contains the number of the next page: either the value set by a @code{pn} request, or the number of the current page plus 1. @findex pc The @code{pc} request will change the page number character (used by the @code{tl} request) to a different character. With no argument, this mechanism is disabled. @c distribute these through the text @xref{Traps} @node Page Control, Fonts, Page Layout, Programming Tutorial @section Page Control @cindex page control @cindex control, page @findex bp To stop processing the current page, and move to the next page, you can invoke the @code{bp} request. This request will also cause a break. This request can also take an argument of what the next page should be numbered. The only difference between @code{bp} and @code{pn} is that @code{pn} does not cause a break or actually eject a page. @example .de newpage 'bp 'sp .5i .tl 'left top'center top'right top' 'sp .3i .. @end example @cindex orphan @findex ne Often you may want to make sure that you have a certain amount of space before a new page occurs. This is most useful to make sure that there is not a single @dfn{orphan} line left at the bottom of a page. The @code{ne} request will ensure that there is a certain distance, specified by the first argument, before the next page is triggered (@pxref{Traps}, for further information). The default unit for @code{ne} is v's and the default argument is 1v. For example, to make sure that no fewer than 2 lines get orphaned, you can do the following before each paragraph. @example .ne 2 .ti +5n text @end example @findex sv @findex os The @code{sv} is similar to the @code{ne} request, it reserves the specified amount of vertical space. If the desired amount of space exists before the next trap (bottom page boundary), the space will be output immediately. If there is not enough space, it is stored for later output via the @code{os} request. The default argument is 1v and the default units are v's. @node Fonts, Sizes, Page Control, Programming Tutorial @section Fonts @cindex fonts @findex ft @findex \f Groff gives you the ability to switch fonts at any point in your text. There are two ways to do this, via the @code{ft} request and the @code{\f} escape. Fonts are generaly specified as uppercase strings, which are usually 1 to 4 characters representing an abreviation of acronym of the font name. The basic set of fonts are R, I, B, and BI. These are Times Roman, Italic, Bold, and Bold Italic. There is also at least one symbol font which contains various special symbols (greek, mathematics). These latter fonts cannot be used directly, but should be used via an escape. @menu * Changing Fonts:: * Font Families:: * Font Positions:: * Using Symbols:: * Artificial Fonts:: * Ligatures and Kerning:: @end menu @node Changing Fonts, Font Families, Fonts, Fonts @subsection Changing Fonts @cindex changing fonts @cindex fonts, changing @findex ft You can change fonts with both the @code{ft} request. With no arguments it will switch to the previous font (also known as P). @example eggs, bacon, .ft B spam .ft and sausage. @end example @findex \f The @code{\f} escape is useful for changing fonts in the middle of words @example eggs, bacon, \fBspam\fP and sausage. @end example Both of the above examples will produce the same output. Sometimes when putting letters of different fonts, you need more or less space at such boundaries. There are two escapes to help with this. @findex \/ The @code{\/} escape increases the width of the preceding character so that the spacing between that character and the following character will be correct if the following character is a roman character. For example, if an italic f is immediately followed by a roman right parenthesis, then in many fonts the top right portion of the f will overlap the top left of the right parenthesis. It is a good idea to use this escape sequence whenever an italic character is immediately followed by a roman character without any intervening space. @c producing @i{f}), which is ugly. Inserting \/ produces f) and avoids this problem. @findex \, The @code{\,} escape modifies the spacing of the following character so that the spacing between that character and the preceding character will correct if the preceding character is a roman character. It is a good idea to use this escape sequence whenever a roman character is immediately followed by an italic character without any intervening space. @c For example, inserting \, between the parenthesis and the f changes (f to (f. @findex ftr The @code{ftr} request will translate fonts, it is called as @samp{.ftr @var{F G}}, which Translate font @var{F} to @var{G}. Whenever a font named @var{F} is referred to in @code{\f} escape sequence, or in the @code{ft}, @var{ul}, @var{bd}, @var{cs}, @var{tkf}, @var{special}, @var{fspecial}, @var{fp}, or @var{sty} requests, font @var{G} will be used. If @var{G} is missing, or equal to @var{F} then font @var{F} will not be translated. @node Font Families, Font Positions, Changing Fonts, Fonts @subsection Font Families @cindex font families @cindex families, font Due to the variety of fonts available, groff has added the concept of font families. Each of these families has four styles (R, I, B and BI), The fonts are specified as the concatenation of the font family and style. Specifying a font without the family part will cause groff to use that style of the current family. By default, groff uses the Times family. This way, you can just use the basic four fonts and select a different font family on the command line. @findex fam @vindex .fam You can also switch font families with the @code{fam} request The current font family is available in the number register @code{.fam}. This is a string-valued register. @example spam, .fam H spam, .ft B spam, .fam T spam, .ft AR baked beans, .ft R and spam. @end example @node Font Positions, Using Symbols, Font Families, Fonts @subsection Font Positions @cindex font positions @cindex positions, font For the sake of old phototypesetters and compatability with old versions of troff, groff has the concept of font @dfn{positions}, on which various fonts are mounted. The last one or two are reserved for the symbol font(s). @findex fp New fonts can be mounted with the @code{fp} request. These numeric positions can then be referred to with font changing commands. When groff starts it is using font number one. @example .fp 1 H .fp 2 HI .fp 3 HB wink, wink, .ft 2 nudge, nudge, .ft .ft 3 say no more! .ft @end example (note that after these font changes have taken place the original font is restored.) @vindex .f The current font in use, as a font position. This can be useful to remember the current font, for later recall. @example .nr save-font \n(.f ... lots 'o text ... .ft \n[save-font] @end example @vindex .fp The number of the next free font position is available in the number register @code{.fp}. This is useful when mounting a new font, like so: @example .fp \n[.fp] NEATOFONT @end example @pindex DESC Fonts not listed in the @file{DESC} file are automatically mounted on the next available font position when they are referenced. If a font is to be mountfed explicitly with the @code{fp} request on an unused font position, it should be mounted on the first unused font position, which can be found in the @code{.fp} register; although troff does not enforce this strictly, it will not allow a font to be mounted at a position whose number is much greater than that of any currently used position. The @code{fp} request has an optional third argument. This argument gives the external name of the font, which is used for finding the font description file. The second argument gives the internal name of the font which is used to refer to the font in troff after it has been mounted. If there is no third argument then the internal name will be used as the external name. This feature allows you to use fonts with long names in compatibility mode. @node Using Symbols, Artificial Fonts, Font Positions, Fonts @subsection Using Symbols @cindex using symbols @cindex symbols, using @findex \( @findex \[ Symbols can be inserted by using a special escape sequence. This escape is simply the escape character (a backslash) followed by an identifier. The symbol identifiers have to be two or more characters, since single characters conflict with all the other escapes. The identifier can be either preceded by a parenthesis if it is two character, or surrounded by square brackets. So, the symbol for pi can be produced either by @code{\(*p} or @code{\[*p]}. @example area = \(*p\fIr\fP\u2\d @end example @findex \C The escape @code{\C'@var{xxx}'} will typeset character named @var{xxx}. Normally it is more convenient to use @code{\[@var{xxx}]}. But @code{\C} has the advantage that it is compatible with recent versions of ditroff and is available in compatibility mode. @findex \N The escape @code{\N'@var{n}'} will typeset the character with code @var{n} in the current font. @var{n} can be any integer. Most devices only have characters with codes between 0 and 255. If the current font does not contain a character with that code, special fonts will not be searched. The @code{\N} escape sequence can be conveniently used on conjunction with the @code{char} request: @example .char \[phone] \f(ZD\N'37' @end example The code of each character is given in the fourth column in the font description file after the charset command. It is possible to include unnamed characters in the font description file by using a name of @samp{---}; the @code{\N} escape sequence is the only way to use these. @findex cflags Each character has certain properties associated with it. These properties can be modified with the @code{cflags} request. The first argument is the the sum of the desired flags and the remaining arguments are the characters to have those properties. @table @code @item 1 the character ends sentences (initially characters @samp{.?!} have this property); @item 2 lines can be broken before the character (initially no characters have this property); @item 4 lines can be broken after the character (initially characters @samp{-\(hy\(em} have this property); @item 8 the character overlaps horizontally (initially characters @samp{\(ul\(rn\(ru} have this property); @item 16 the character overlaps vertically (initially character @samp{\(br} has this property); @item 32 an end of sentence character followed by any number of characters with this property will be treated as the end of a sentence if followed by a newline or two spaces; in other words the character is transparent for the purposes of end of sentence recognition; this is the same as having a zero space factor in @TeX{} (initially characters @samp{"')]*\(dg\(rq} have this property). @end table @findex char You can create new characters with the @code{char} request. It is called as @samp{.char @var{c} @var{string}} Define character @var{c} to be @var{string}. Every time character @var{c} needs to be printed, @var{string} will be processed in a temporary environment and the result will be wrapped up into a single object. Compatibility mode will be turned off and the escape character will be set to \ while @var{string} is being processed. Any emboldening, constant spacing or track kerning will be applied to this object rather than to individual characters in @var{string}. A character defined by this request can be used just like a normal character provided by the output device. In particular other characters can be translated to it with the @code{tr} request; it can be made the leader character by the @code{lc} request; repeated patterns can be drawn with the character using the @code{\l} and @code{\L} escape sequences; words containing the character can be hyphenated correctly, if the @code{hcode} request is used to give the character a hyphenation code. There is a special anti-recursion feature: use of character within the character's definition will be handled like normal characters not defined with @code{char}. @findex rchar A character definition can be removed with the @code{rchar} request. Its arguments are the characters to be removed. This undoes the effect of a @code{char} request. @c distribute these through the text @xref{Special Characters} @node Artificial Fonts, Ligatures and Kerning, Using Symbols, Fonts @subsection Artificial Fonts @cindex artificial fonts @cindex fonts, artificial There are a number of requests for artificially creating fonts. These are largely vestigal remains from the days when output devices did not have a wide variety of fonts, and when nroff and troff were separate programs. These are no longer necessary in GNU Troff. @findex ul The @code{ul} request will print subsequent lines in italics on a device capable of it, or underline the text on an ascii output device. The single argument is the number of lines to be ``underlined,'' with no argument, the next line will be underlined. @findex cu The @code{cu} request is similar to @code{ul} ... @findex uf The @code{uf} request will set the underline font used by @code{ul} and @code{cu}. @findex bd The @code{bd} request artificially creates a bold font by printing each character twice, slightly offset. The first argument specifies the font to embolden, and the second is the number of basic units, minus one, by which the two characters will be offset. If the second argument is missing, emboldening will be turned off. @node Ligatures and Kerning, , Artificial Fonts, Fonts @subsection Ligatures and Kerning @cindex ligatures and kerning @cindex kerning and ligatures @findex lg @vindex .lg @code{lg} @code{.lg} The current ligature mode. What is kerning?? If the font description file contains pairwise kerning information, characters from that font will be kerned. Kerning between two characters can be inhibited by placing a @code{\&} between them. @findex kern @vindex .kern @code{kern} If n is non-zero or missing, enable pairwise kerning, otherwise disable it. @code{.kern} 1 if pairwise kerning is enabled, 0 otherwise. @findex tkf .tkf f s1 n1 s2 n2 Enable track kerning for font f. When the current font is f the width of every character will be increased by an amount between n1 and n2; when the current point size is less than or equal to s1 the width will be increased by n1; when it is greater than or equal to s2 the width will be increased by n2; when the point size is greater than or equal to s1 and less than or equal to s2 the increase in width is a linear function of the point size. @node Sizes, Strings, Fonts, Programming Tutorial @section Sizes @cindex sizes @cindex baseline Groff uses two dimensions with each line of text, type size and vertical spacing. The type size is the height from the text @dfn{baseline} to the top of the tallest character (decenders may drop below this baseline). Vertical spacing is the amount of space groff allows for a line of text, normally, this is about 20% larger than the current type size. Ratios smaller than this can result in hard-to-read text, larger that this, it will spread your text out more vertically (useful for term papers). By default, troff uses 10 point type on 12 point spacing. @cindex leading The difference between type size and vertical spacing is known, by typesetters, as @dfn{leading}. @menu * Changing Type Sizes:: * Fractional Type Sizes:: @end menu @node Changing Type Sizes, Fractional Type Sizes, Sizes, Sizes @subsection Changing Type Sizes @cindex changing type sizes @cindex type sizes, changing @findex ps @findex vs @findex \s @vindex .s @vindex .v Using the @code{ps} request and the @code{\s} escape you can change the type size. The @code{vs} request will change the vertical spacing. The default unit for the @code{ps} and @code{vs} requests are points. The number registers @code{.s} and @code{.v} contain the current type size and vertical spacing. These requests take parameters in units of points. You can specify sizes as an absolute size, or as a relative change from the current size. The size 0 means go back to the previous size. With no argument it will revert to the previous size. @example snap, snap, .ps +2 grin, grin, .ps +2 wink, wink, \s+2nudge, nudge,\s+8 say no more! .ps 10 @end example The @code{\s} escape may be called in a variety of ways. Much like other escapes there must be a way to determine where the argument ends and the text begins. Any of the following forms are valid: @code{\s@var{n}}, @code{\s+@var{n}}, @code{\s-@var{n}}, @code{\s(@var{nn}}, @code{\s+(@var{nn}}, @code{\s-(@var{nn}}, @code{\s[+@var{nnn}]}, @code{\s[-@var{nnn}]}, @code{\s+[@var{nnn}]}, @code{\s-[@var{nnn}]}. Some devices may only have certain permissible sizes, in which case groff will round to the nearest permissible size. @example ... .sz macro example?? ... @end example @node Fractional Type Sizes, , Changing Type Sizes, Sizes @subsection Fractional Type Sizes @cindex fractional type sizes @cindex type sizes, fractional A @dfn{scaled point} is equal to 1/@var{sizescale} points, where @var{sizescale} is specified in the @file{DESC} file (1 by default.) There is a new scale indicator @samp{z} which has the effect of multiplying by @var{sizescale}. Requests and escape sequences in troff interpret arguments that represent a pointsize as being in units of scaled points, but they evaluate each such argument using a default scale indicator of @samp{z}. Arguments treated in this way are the argument to the @code{ps} request, the third argument to the @code{cs} request, the second and fourth arguments to the @code{tkf} request, the argument to the @code{\H} escape sequence, and those variants of the @code{\s} escape sequence that take a numeric expression as their argument. For example, suppose @var{sizescale} is 1000; then a scaled point will be equivalent to a millipoint; the request @samp{.ps 10.25} is equivalent to @samp{.ps 10.25z} and so sets the pointsize to 10250 scaled points, which is equal to 10.25 points. The number register @code{\n(.s} returns the pointsize in points as decimal fraction. There is also a new number register @code{\n[.ps]} that returns the pointsize in scaled points. It would make no sense to use the @samp{z} scale indicator in a numeric expression whose default scale indicator was neither @samp{u} nor @samp{z}, and so troff disallows this. Similarily it would make no sense to use a scaling indicator other than @samp{z} or @samp{u} in a numeric expression whose default scale indicator was @samp{z}, and so troff disallows this as well. There is also new scale indicator @samp{s} which multiplies by the number of units in a scaled point. So, for example, @samp{\n[.ps]s} is equal to 1m. Be sure not to confuse the @samp{s} and @samp{z} scale indicators. @code{\s'+@var{n}'} @code{\s'-@var{n}'} @code{\s+'@var{n}'} @code{\s-'@var{n}'} Set the point size to @var{n} scaled points; @var{n} is a numeric expression with a default scale indicator of @samp{z}. @code{\n[.ps]} The current pointsize in scaled points. @code{\n[.psr]} The last-requested pointsize in scaled points. @code{\n[.sr]} The last requested pointsize in points as a decimal fraction. This is a string-valued register. @c distribute these through the text @xref{Font Files} @node Strings, Conditionals and Loops, Sizes, Programming Tutorial @section Strings @cindex strings @findex ds Groff has string variables, which are entirely for user convenience (i.e. there are no builtin strings) They are defined via the @code{ds} request. @example .ds UX \s-1UNIX\s0\u\s-3tm\s0\d @end example @findex \* The are interpolated, or expanded in-place, via the @code{\*} escape: @example The \*(UX Operating System @end example Will produce: @example The UNIXtm Operating System @end example If the string named by the @code{\*} does not exist, the escape will be replaced by nothing. @cindex comments, with @code{ds} NOTE: Unlike other requests the third argument takes up the entire line including trailing spaces. This means that comments on a line with such a request can introduce unwanted space into a string. @example .ds UX \s-1UNIX\s0\u\s-3tm\s0\d \" trademark of you-know-who @end example Instead you should either put the comment on another line or have the comment escape adjacent with the end of the string. @example .ds UX \s-1UNIX\s0\u\s-3tm\s0\d\" trademark of you-know-who @end example If you need leading space you can start the string with a double quote. No trailing quote is needed, in fact any trailing quote is included in your string. @cindex canibalism @example .ds sign " Yours in a white wine sauce, @end example @findex as @cindex appending to strings @cindex strings, appending You can also append onto a string with the @code{as} request. It works the same as the @code{ds} request except that it appends the second argument onto the string named by the first argument. @example .as sign " with shallots, onions and garlic, @end example @findex \@key{ret} Strings are not limited to a sigle line of text. A string can span several lines by escaping the newlines with a backslash. The resulting string will be stored @emph{without} the newlines. @example .ds foo lots and lots \ of text are on these \ next several lines @end example @findex rn @code{rn} @findex rm @code{rm} @findex als @code{als} @findex chop @code{chop} @c distribute these through the text @xref{Identifiers} @c distribute these through the text @xref{Comments} @node Conditionals and Loops, Writing Macros, Strings, Programming Tutorial @section Conditionals and Loops @cindex conditionals and loops @cindex loops and conditionals @findex if @findex while In @code{if} and @code{while} requests, there are several more operators available: @table @code @item e @itemx o True if the current page is even or odd numbered (respectively) @item n @itemx t True if the document is being processed by nroff (or an ascii device) or troff. @item '@var{xxx}'@var{yyy}' True if the string @var{xxx} is equal to the string @var{yyy}. Other characters can be used in place of the single quotes. (Which?) The strings are `formatted' before being compared. (?) @item r@var{xxx} True if there is a number register named @var{xxx}. @item d@var{xxx} True if there is a string, macro, diversion, or request named @var{xxx}. @item c@var{ch} True if there is a character @var{ch} available; @var{ch} is either an ASCII character or a special character @code{\(@var{ch}} or @code{\[@var{ch}]}; the condition will also be true if @var{ch} has been defined by the @code{char} request. @end table @menu * if-else:: * while:: @end menu @node if-else, while, Conditionals and Loops, Conditionals and Loops @subsection if-else @cindex if-else Troff has if-then-else constructs like other languages, although the formatting can be painful. @findex if The @code{if} request is troff's if statement, it is called as @samp{.if @var{expr} @var{anything}}, where @var{expr} is the expression to be evaluated, and @var{anything} (the remainder of the line) which will be executed if the @var{expr} evaluates to non-zero (true). @var{anything} will be interpreted as though it was on a line by itself. @xref{Expressions}, for more info. Here are some examples: @example .if t .ls 2 \" double spacing in troff .if 0 .ab how'd this happen?? @end example @findex ie @findex el An if-then-else is written using two requests @code{ie} and @code{el} the first request is the if part and the latter is the else part. @example .ie .el @end example @findex \@{ @findex \@} In many cases you will want more than one request to be executed as a result of any of these requests, this can be done using the \@{ and \@} escapes. The following example shows the possible ways to use these escapes. @example .ie t \@{\ . ds lq `` . ds rq '' .\@} .el \ .\@{\ . ds lq " . ds rq "\@} .ds qq " @end example @c distribute these through the text @xref{Expressions} @node while, , if-else, Conditionals and Loops @subsection while @cindex while @findex while Groff provides a looping construct using the @code{while} request, which is used much like the @code{if} (and related) requests. The first argument is an expression which will be evaluated. The @code{while} request will interpret the remainder of the line until the expression evaluates to 0 or false. @example .nr a 0 1 .while (\na<9) \&\n+a, \&\n+a @end example The preceding example produces: @example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 @end example @findex break @findex continue The @code{break} request will @dfn{break} out of a while loop. Be sure not to confuse this with the @code{.br} request. The @code{continue} request will finish the current iteration of a while loop. @c distribute these through the text @xref{Expressions} @node Writing Macros, Page Motions, Conditionals and Loops, Programming Tutorial @section Writing Macros @cindex writing macros @cindex macros, writing @findex de A macro is a collection of text and embedded commands which can be invoked multiple times. Macros are used for defining common operations. Macros are defined using the @code{de} request. This request takes a name for the macro as the first argument. Subsequent lines are copied into an internal buffer until the line @code{..} is encountered. The optional second argument to @code{de} can change this ending token. For example, suppose at the beginning of each paragraph, you want cause a break, move down a partial line and indent the first line. Such a macro could be defined as follows: @example .de P .br .sp .8v .. @end example @findex am The @code{am} request works similarily to @code{de} except it appends onto the macro named by the first argument. So, if we decide we want our previously @code{P} macro to actually do indented instead of block paragraphs we can add the necessary code to our existing macro. @example .am P .ti +5n .. @end example @findex als @cindex aliases, macro @cindex macro aliases Macros can be aliased with the @code{als} request. @findex rn @code{rn} @findex rm @code{rm} @findex chop @code{chop} @menu * Copy-in Mode:: * Parameters:: @end menu @node Copy-in Mode, Parameters, Writing Macros, Writing Macros @subsection Copy-in Mode @cindex copy-in mode @cindex mode, copy-in @findex \n @findex \$ @findex \* @findex \\ @findex \@key{RET} When troff reads in the test for a macro or diversion it copies the text (including request lines) into an internal buffer, except for escapes. Escapes will be converted into an internal form, except for @code{\n}, @code{\$}, @code{\*}, @code{\\} and @code{\@key{RET}} which are evaluated and inserted into the text where the escape was located. This is known as @dfn{copy-in} mode. What this means is that you can specify when these escapes are to be evaluated (copy-in time or time of use) by insulating the escapes with an extra backslash. For example, the following will result in the numbers 20 and 10 being printed. @example .nr x 20 .de y .nr x 10 \&\nx \&\\nx .. .y @end example @node Parameters, , Copy-in Mode, Writing Macros @subsection Parameters @cindex parameters @findex \$ @vindex .$ The arguments to a macro can be examined using a variety of escapes. The number of arguments is available in the @code{.$} number register. Any individual argument can be retrieved with one of the following escapes: The escapes @code{\$@var{n}}, @code{\$(@var{nn}} and @code{\$[@var{nnn}]} will result in the @var{n}th, @var{nn}th or @var{nnn}th argument. Macros can have a unlimited number of arguments. Note that due to copy-in mode, you will want to have two backslashes on these in actual use, since you do not want them interpolated until the macro is actually invoked. @findex shift The request @code{shift} will shift the arguments 1 position, or as many positions as specified by the first argument. After executing this request, argument @var{i} will become argument @var{i}-@var{n}; arguments 1 to @var{n} will no longer be available. Shifting by negative amounts is currently undefined. @findex \$* @findex \$@@ In some cases you will want to just use all of the arguments at once. For example if you pass the arguments along to another macro. The @code{\$*} escape is the concatenation of all the arguments separated by spaces. A similar escape is @code{\$@@}, which is the concatenation of all the arguments with each surrounded by double quotes, and separated by spaces. @findex \$0 @findex als The @code{\$0} escape is the name by which the current macro was invoked. The @code{als} request can make a macro have more than one name. @example .de vl .ie \\n(.$=1 .ds Vl Pre-Release Version .el .ds Vl Version \\$3, \\$4. .. @end example This would be called as @example .vl $Id: groff.texinfo,v 1.2 2000/04/09 08:25:11 millert Exp $ @end example @c distribute these through the text @xref{Request Arguments} @node Page Motions, Drawing Functions, Writing Macros, Programming Tutorial @section Page Motions @cindex page motions @cindex motions, page @findex sp Motions up and down the page can be done with the @code{sp} request. However, this causes a break so that the actual effect is to move to the left margin and then to the specified location. @findex mk @findex rt The request @code{mk} can be used to mark a location on a page, for movement to later. This request takes a register name as an argument in which to store the current page location, with no argument it will store the location in an internal register. The results of this can be used later by the @code{rt} or the @code{sp} request. The @code{rt} request will return @strong{upwards} to the location given in the register name given as an argument, with no argument it will return to the location marked with the @code{mk} request @example ... dual column example ... @end example There are escapes which will give you much finer control of movements about the page. @findex \v The @code{\v'@var{e}'} will let you do arbitrary vertical motion from the current location on the page. The argument @var{e} specifies the distance to move, positive is downwards and negative upwards. The default unit for this escape is vertical spaces, @code{v}'s. Beware, however, that troff will leave text processing to continue wherever the motion ends, so if you don't want to interfere with text processing, make sure your motions are balanced. There are some special case escapes for vertical motion. @ftable @code @item \r move upwards 1v. @item \u move upwards .5v. @item \d move down .5v. @end ftable @findex \h Horizontal motions can be done via the @code{\h'@var{e}'} escape. The expression @var{e} indicates how far to move: positive is rightwards and negative leftwards. There are a number of special case escapes for horizontal motion: @ftable @code @item \@key{SP} An unbreakable and unpadable (i.e. not expanded during filling) space. (Note: it is a backslash followed by a space.) @item \~ This produces an unbreakable space that stretches like a normal interword space when a line is adjusted. @item \| a 1/6th em space. @item \^ a 1/12th em space. @item \0 a space the size of a digit. @item \& A zero width space. @item \) Like @code{\&} except that it behaves like a character declared with the @code{cflags} request to be transparent for the purposes of end of sentence recognition. @end ftable @example ... tex logo example ... @end example @findex \w @cindex width escape @cindex escape, width Often you will want to do horizontal movement based on the width of some arbitrary text (e.g. given as an argument to a macro). For that, there is the escape @code{\w'@var{text}'} which will interpolate to the width of the given @var{text} in basic units. @example ... strlen example ... @end example Font changes may occur in @var{text} and not affect current settings. Also after use, @code{\w} sets several registers: @table @code @item st @vindex st @itemx sb @vindex sb The highest and lowest point, respectively, in @var{text}. @item rst @vindex rst @itemx rsb @vindex rsb Like the @code{st} and @code{sb} registers, but takes account of the heights and depths of characters. @item ct @vindex ct is set according to what kinds of characters occur in @var{text}. @table @asis @item 0 all short characters, no decenders or tall characters. @item 1 decender @item 2 tall character @item 3 both a decender and a tall character @end table @item ssc @vindex ssc The amount of horizontal space (possibly negative) that should be added to the last character before a subscript. @item skw @vindex skw How far to right of the center of the last character in the @code{\w} argument, the center of an accent from a roman font should be placed over that character. @end table @findex \k @vindex .k @code{\k} @code{.k} @node Drawing Functions, Traps, Page Motions, Programming Tutorial @section Drawing Functions @cindex drawing functions @cindex functions for drawing Groff provides a number of ways to draw lines, and other figures on the page. Used in combination with the page motion commands (@pxref{Page Motions}, for more info) you can draw a wide variety of figures. However, for complex drawings these operations can be quite cumbersome, and it may be wise to use the pic preprocessor. @xref{gpic}, for more information. All drawing is done via escapes. @findex \l The @code{\l} will draw a line rightwards from the current location. The full syntax for this escape is @samp{\l'@var{l}@var{c}'}, where @var{l} is the length of the line to be drawn, starting at the current location, positive numbers will draw to the right, and negative will draw towards the left. This can also be specified absolutely (i.e. with a leading |) which will draw back to the begining of the line. The optional second parameter @var{c} is a character to draw the line with. If this second argument is not specified, troff will use the underscore character. If you need to separate the two arguments (to prevent troff from interpreting a drawing character as a scaling indicator), you can separate them with @code{\&}. And now, for a useful example: @example .de box \(br\\$*\(br\l'|0\(rn'\l'|0\(ul' .. @end example Note that this works by outputing a box rule (a vertical line), then the text given as an argument and then another box rule. Then the line drawing escapes both draw from the current location to the beginning of the @emph{input} line. @findex \L Vertical lines are drawn using the @code{\L} escape. It's parameters are specified the same as the @code{\l} escape. If the length is positive, the movement will be downwards, and upwards for negative. The default character is the box rule character. As with the vertical motion escapes, text processing will blindly continue where the line ends. @example ...box macro... @end example @findex \D More flexible drawing functions are available via the @code{\D} escape. While the previous escapes will work on an ascii device, these escapes will not. @table @code @item \D'l @var{x} @var{y}' Draw a line from the current location to the relative point specified by @var{x}, @var{y}. @example ...revised box macro... @end example @item \D'c @var{d}' Draw a circle with a diameter of @var{d} with the leftmost point at the current position. @item \D'C @var{d}' Draw a solid circle with the same parameters as an outlined circle. @item \D'e @var{dx} @var{dy}' Draw an ellipse with a horizontal diameter of @var{dx} and a vertical diameter of @var{dy} with the leftmost point at the current position. @item \D'E @var{dx} @var{dy}' Draw a solid elipse with the same parameters as an outlined elipse. @item \D'a @var{dx1} @var{dy1} @var{dx2} @var{dy2}' Draw an arc clockwise from the current location through the two specified locations. @item \D'~ @var{dx1} @var{dy1} @var{dx2} @var{dy2} ...' Draw a spline from the current location to @var{dx1}, @var{dy1} and then to @var{dx2}, @var{dy2}, and so on. @item \D'f @var{n}' Set the shade of gray to be used for filling solid objects to @var{n}; @var{n} must be an integer between 0 and 1000, where 0 corresponds solid white and 1000 to solid black, and values in between correspond to intermediate shades of gray. This applies only to solid circles, solid ellipses and solid polygons. By default, a level of 1000 will be used. @item \D'p @var{dx1} @var{dy1} @var{dx2} @var{dy2} ...' Draw a polygon from the current location to @var{dx1}, @var{dy1} and then to @var{dx2}, @var{dy2} and so on. When the specified data points are exhausted, a line is drawn back to the starting point. @example ... box example (yes, again)... @end example @itemx \D'P @var{dx1} @var{dy1} @var{dx2} @var{dy2} ...' Draw a solid polygon with the same parameters as an outlined polygon. @example ... shaded box example ... @end example @item \D't @var{n}' Set the current line thickness to @var{n} machine units. A value of zero selects the smallest available line thickness. @end table Current position @findex \b @cindex pile, character @cindex character pile The @code{\b} escape will @dfn{pile} a sequence of characters vertically, and center it vertically on the current line. This can be used to build large brackets and braces. @example \b'\(lt\(bv\(lk\(bv\(lb' @end example @node Traps, Diversions, Drawing Functions, Programming Tutorial @section Traps @cindex traps Traps are locations, which, when reached, will call a specified macro. These traps can occur at a given location on the page, at a given location in the current diversion, after a certain number of input lines or at the end of input. @findex ch Any of these traps can be changed after they have been set with the @code{ch} request. The first arguemnt is the name of the trap or macro, and the second is the new value for that trap. @menu * Page Location Traps:: * Diversion Traps:: * Input Line Traps:: * End-of-input Traps:: @end menu @node Page Location Traps, Diversion Traps, Traps, Traps @subsection Page Location Traps @cindex page location traps @cindex traps, page location Page location traps are frequently used for page headers and footers. The following is a simple example of this. @example .de hd \" Page header 'sp .5i .tl 'Title''date' 'sp .3i .. .de fo \" Page footer 'sp 1v .tl ''%'' 'bp .. .wh 0 hd \" top of the page .wh -1i fo \" one inch from bottom @end example @vindex .t The number register @code{.t} is the distance to the next trap. @findex ch The location of a trap can be changed later on with the @code{ch} request. The first argument is the name of the macro to be invoked at the trap and the second argument is the new location for the trap. This is useful when you are building up footnotes in a diversion, and you need to allow more space at the bottom of the page for them. @example ... (simplified) footnote example ... @end example @findex vpt @findex wh @findex dt @vindex .vpt The @code{vpt} request will enable vertical position traps if the argment is non-zero, disable them otherwise. Vertical position traps are traps set by the @code{wh} or @code{dt} requests. Traps set by the @code{it} request are not vertical position traps. The parameter that controls whether vertical position traps are enabled is global. Initially vertical position traps are enabled. The current setting of this is available in the number register @code{.vpt}. @vindex .trunc @findex ne The number register @code{.trunc} contains the amount of vertical space truncated by the most recently sprung vertical position trap, or, if the trap was sprung by a @code{ne} request, minus the amount of vertical motion produced by the @code{ne} request. In other words, at the point a trap is sprung, it represents the difference of what the vertical position would have been but for the trap, and what the vertical position actually is. @vindex .ne The number register @code{.ne} contains the amount of space that was needed in the last @code{ne} request that caused a trap to be sprung. Useful in conjunction with the @code{.trunc} register. @xref{Page Control}, for more information. @node Diversion Traps, Input Line Traps, Page Location Traps, Traps @subsection Diversion Traps @cindex diversion traps @cindex traps, diversion @findex dt @vindex .t Traps can also be set @emph{within} a diversion using the @code{dt} request. Like @code{wh} the first argument is the location of the trap and the second argument is the name of the macro to be invoked. The number register @code{.t} will still work within diversions. @xref{Diversions}, for more information. @node Input Line Traps, End-of-input Traps, Diversion Traps, Traps @subsection Input Line Traps @cindex input line traps @cindex traps, input line @findex it The @code{it} request will set an input line trap. The format for calling this is @samp{.it @var{n} @var{name}}, where @var{n} is the number of lines of input which may be read before @dfn{springing} the trap, @var{name} is the macro to be invoked. Request lines are not counted as input lines. For example, one possible use is to have a macro which will print the next @var{n} lines in a bold font. @example .de B .it B-end \\$1 .ft B .. .de B-end .ft R .. @end example @node End-of-input Traps, , Input Line Traps, Traps @subsection End-of-input Traps @cindex end-of-input traps @cindex traps, end-of-input @findex em The @code{em} request will set a trap at the end of input. The macro specified as an arguement will be executed after the last line of the input file has been processed. For example, if your document had to have a section at the bottom of the last page for someone to approve you document, you could set it up with @code{em}. @example .de approval .ne 5v .sp |(\\n(.t-6v) .in +4i .lc _ .br Approved:\t\a .sp Date:\t\t\a .. .em approval @end example @node Diversions, Environments, Traps, Programming Tutorial @section Diversions @cindex diversions In Troff you can divert text into a named storage area, due to the similarity to defining macros it is sometimes said to be stored in a macro. This is used for saving text for output at a later time, which is useful for keeping blocks of text on the same page, footnotes, tables of contents and indexes. @findex di @findex da Diversion is initiated by the @code{di} request, like the @code{de} request it takes an argument of a macro name to divert subsequent text to into. The @code{da} macro will append to an existing diversion. @example ... end-note example ... @end example @vindex .z @vindex .d @vindex nl @vindex .h Diversions may be nested. The number register @code{.z} contains the name of the current diversion. The number register @code{.d} contains the current vertical place in the diversion. If not in a diversion it is the same as the register @code{nl}. @code{.h} @vindex dn @vindex dl After compleating a diversion, the builtin number registers @code{dn} and @code{dl} contain the vertical and horizontal size of the diversion. @example .\" Center text both horizontally & vertically .de (c .br .nf .di @@c .. .de )c .br .di .nr @@s (((\\n(.tu-\\n(dnu)/2u)-1v) .sp \\n(@@su .ce 1000 .nf .@c .br .ce 0 .sp \\n(@@su .br .fi .rr @@s .. @end example @findex \! Requests, macros and escapes are interpreted when read into a diversion. There are two ways to prevent this, either way will take the given text and @dfn{transparently} embed it into the diversion. The first method is to prefix the line with @code{\!}. This will cause the entire line to be transparently inserted into the diversion. This is useful for macros you do not want invoked until the diverted text is actually output. @c anything is read in copy mode. (what about \! ??) @findex \? The other way is to surround the text by the @code{\?} escape, i.e. @samp{\?@var{anything}\?}. @var{anything} may not contain newlines; use @code{\!} if you want to embed newlines in a diversion. The escape sequence @code{\?} is also recognised in copy mode and turned into a single internal code; it is this code that terminates anything. Thus the followin example will print 4. @example .nr x 1 .nf .di d \?\\?\\\\?\\\\\\\\nx\\\\?\\?\? .di .nr x 2 .di e .d .di .nr x 3 .di f .e .di .nr x 4 .f @end example @findex rn @code{rn} @findex rm @code{rm} @findex als @code{als} @findex chop @code{chop} @findex asciify @code{asciify} This request only exists in order to make it possible to make certain gross hacks work with GNU troff. It @dfn{unformats} the diversion specified as an argument in such a way that ASCII characters that were formatted and diverted will be treated like ordinary input characters when the diversion is reread. For example, the following will set register @code{n} to 1. @example .tr @@. .di x @@nr\ n\ 1 .br .di .tr @@@@ .asciify x .x @end example @c distribute these through the text @xref{Copy-in Mode} @node Environments, I/O, Diversions, Programming Tutorial @section Environments @cindex environments Often you will need to print some text in a certain format regardless of what may be in effect at the time, for example, in a trap invoked macro to print headers and footers. To solve this groff has @dfn{environments} in which text is processed. An environment contains most of the parameters that control text processing. You can switch amongst these environments, by default groff processes text in environment 0. The following is the information kept in an environment. @itemize @bullet{} @item Type size @item Font (family and style) @item Page parameters @item Fill/adjust mode @item Tab stops @item Partially collected lines @end itemize These environments may be given arbitrary names (@pxref{Identifiers}, for more info.) Old versions of troff only had environments named 0, 1 and 2. @findex ev @vindex .ev The @code{ev} request will switch among these environments. The single argument is the name of the environment to switch to, with no argument groff will switch back to the previous enviroment. There is no limit on the number of named environments; they will be created the first time that they are referenced. The @code{.ev} number register contains the name or number of the current environment. This is a string-valued register. @example ... page break macro, revised ... @end example @example .ev footnote-env .fam N .ps 6 .vs 8 .ll -.5i .ev ... .ev footnote-env \(dg Note the large, friendly letters. .ev @end example @node I/O, Postprocessor Access, Environments, Programming Tutorial @section I/O @cindex i/o @findex so The @code{so} request will read in the file given as an argument and include it in place of the @code{so} request. This is quite useful for large documents, i.e. keeping each chapter in a separate file. @xref{gsoelim}, for more information. @findex mso The @code{mso} request is the same as the @code{so} request except that file is searched for in the same way that @file{tmac.@var{name}} is searched for when the @samp{-m@var{name}} option is specified. @findex cf @findex trf The @code{cf} and @code{trf} requests are to include a file. It will transparently output the contents of file filename. Each line is output as it would be were it preceded by @code{\!}; however, the lines are not subject to copy-mode interpretation. If the file does not end with a newline, then a newline will be added. For example, you can define a macro @code{x} containing the contents of file @file{f}, using @example .di x .trf f .di @end example .cf filename When used in a diversion, this will embed in the diversion an object which, when reread, will cause the contents of filename to be transparently copied through to the output. In @sc{Unix} troff, the contents of filename is immediately copied through to the output regardless of whether there is a current diversion; this behaviour is so anomalous that it must be considered a bug. With @code{trf}, unlike @code{cf}, the file cannot contain characters such as NUL that are not legal troff input characters. @findex nx The @code{nx} request will force groff to continue processing of the file specified as an argument. @findex rd The @code{rd} request will read from standard input, and include what is read as though it were part of the input file. Text is read until a blank line is encountered. @cindex form letters @cindex letters, form Using these two requests you can set up form letters. The form letter template is constructed like this: @example .ce \*(td .sp 2 .nf .rd .sp .rd .fi Body of letter. .bp .nx repeat.let @end example @findex ex When this is run, the following file should be redirected in. Note that requests included in this file are executed as though they were part of the form letter. The last block of input is the @code{ex} requests which tells groff to stop processing. If this was not there, groff would not know when to stop. @cindex Beagle Brothers @example Trent A. Fisher 708 NW 19th Av., #202 Portland, OR 97209 Dear Trent, Len Adollar 4315 Sierra Vista San Diego, CA 92103 Dear Mr. Adollar, .ex @end example @findex pi @code{pi} @findex sy The @code{sy} request will allow arbitrary system commands to be executed from within a groff document. The output is not saved anyplace, so it is up to you to do so. For example, the following example will introduce the current time into your document: @cindex time @pindex perl @example .sy perl -e 'printf ".nr H %d\\n.nr M %d\\n.nr S %d\\n",\ (localtime(time))[2,1,0]' > /tmp/x\n[$$] .so /tmp/x\n[$$] .sy rm /tmp/x\n[$$] \nH:\nM:\nS @end example Note that this works by having the perl script (run by @code{sy}) print out the @code{nr} requests which will set the number registers @samp{H}, @samp{M} and @samp{S}, and then reads those commands in with the @code{so} request. @vindex systat The @code{systat} number register contains The return value of the @code{system()} function executed by the last @code{sy} request. @findex open The @code{open} request will open a file (specified as the second argument) for writing and associate the stream (specified as the first argument) with it. @findex opena The @code{opena} is like open, but if filename exists, append to it instead of truncating it. @findex write @findex ds @cindex copy-in mode @cindex mode, copy-in The @code{write} request will write to the file associated with the stream specified by the first argument. The stream must previously have been the subject of an open request. The remainder of the line in interpreted as the @code{ds} request reads its second argument: a leading @code{"} will be stripped, and it will be read in copy-in mode. @findex close The @code{close} request will close the stream specified by the first argument; stream will no longer be an acceptable argument to the @code{write} request. @example ... example of open write &c... @end example @findex \v The @code{\V} escape will interpolate the contents of the specified environment variable, as returned by getenv(3). The argument to @code{\V} is specified as an identifier, i.e. @samp{\V@var{x}}, @samp{\V(@var{xx}} or @samp{\V[@var{xxx}]}. @code{\V} is interpreted in copy-in mode. @node Postprocessor Access, Miscellany, I/O, Programming Tutorial @section Postprocessor Access @cindex postprocessor access @cindex access of postprocessor There are two escapes which will allow you to give information directly to the postprocessor. This is particularly useful for embedding PostScript into your final document. @findex \X The @code{\X} escape will embed its argument into the gtroff output preceded with @samp{x X}. @findex \Y The @code{\Y} escape is called with an identifier (i.e. @code{\Y@var{x}}, @code{\Y(@var{xx}} or @code{\Y[@var{xxx}]}). This is approximately equivalent to @samp{\X'\*[@var{xxx}]'}. However the contents of the string or macro @var{xxx} are not interpreted; also it is permitted for @var{xxx} to have been defined as a macro and thus contain newlines (it is not permitted for the argument to @code{\X} to contain newlines). The inclusion of newlines requires an extetension to the @sc{Unix} troff output format, and will confuse drivers that do not know about this extension. @c distribute these through the text @xref{Devices} @node Miscellany, Debugging, Postprocessor Access, Programming Tutorial @section Miscellany @cindex miscellany This section contains parts of troff which cannot (yet) be categorized elsewhere in this manual. @findex nm Line numbers can be printed in the left margin using the @code{nm} request. The first argument is the line number of the @emph{next} output line, this defaults to 1. The second argument indicates on which lines numbers will be printed, i.e. 5 means put line numbers on every 5 lines, this defaults to 1. The third argument is the space to be left between the number and your text, this defaults to 1. The fourth argument is the indentation of the line numbers. Without arguments, line numbers are turned off. @findex nn The @code{nn} request will temporarily turn off line numbering. The first argument is the number of lines not to be numbered, this defaults to 1. (does this disable incrementing or display?) @example ... line numbering example ... @end example @findex mc margin characters can be automatically printed to the right of your text with the @code{mc} request. The first argument is the character to be printed and the second argument is the distance away from your text. With no arguments the margin characters are turned off. If this occurs before a break, no margin character will be printed. This is quite useful for indicating text that has changed, and, in fact, there are programs available for doing this (they are called @code{nrchbar} and @code{changebar} and can be found in any @samp{comp.sources.unix} archive. @example ... margin char example ... @end example @findex lf @pindex soelim The @code{lf} primary reason for existence is to make debugging documents which are split into many files, which are then put together with @code{soelim} and other preprocessors. The first argument is the name of the file and the second argument is the input line number in that file. This way troff can produce error messages which are intelligible to the user. @example ... example of soelim'ed doc ... @end example @node Debugging, Implementation Differences, Miscellany, Programming Tutorial @section Debugging @cindex debugging Troff is not easy to debug, but there are some useful features and strategies for debugging. @itemize @bullet{} @item @findex tm The @code{tm} request will send output to stderr, this is very useful for printing debugging output. @item When doing something involved it is useful to leave the debugging statements in the code and have them turned on by a command line flag. @example .if \n(DB .tm debugging output @end example Then you can activate these statements with: @example groff -rDB=1 file @end example @item @findex ab The @code{ab} request is similar to the @code{tm} request, except that it will cause groff to stop processing. With no argument it will print @samp{User Abort}. @item @findex ex The @code{ex} request will also cause groff to stop processing. @item If you know you are going to get many errors and no useful output, you can tell groff to suppress formatted output with the @samp{-z} flag. @item @findex pm The @code{pm} request will dump out the entire symbol table. @item @findex pnr The @code{pnr} request will print the names and contents of all currently defined number registers on stderr. @item @findex ptr The @code{ptr} request will print the names and positions of all traps (not including input line traps and diversion traps) on stderr. Empty slots in the page trap list are printed as well, because they can affect the priority of subsequently planted traps. @item @findex fl The @code{fl} request instructs groff to flush its output immediately. The intention is that this be used when using troff interactively. There is little other use for it. @item @findex backtrace The @code{backtrace} request will print a backtrace of the input stack on stderr. @item Groff has command line options for printing out more warnings (@samp{-w}) and for printing backtraces (@samp{-b}) when a warning or an error occurs. The most verbose level of warnings is @samp{-ww}. @item @findex warn @vindex .warn The @code{warn} request controls the level of warnings checked for. The one argument is the sum of the numbers associated with each warning that is to be enabled; all other warnings will be disabled. The number associated with each warning is listed below. For example, @code{.warn 0} will disable all warnings, and @code{.warn 1} will disable all warnings except that about missing characters. If an argument is not given, all warnings will be enabled. The number register @code{.warn} contains the current warning level. @end itemize @subsection Warnings @cindex warnings The warnings that can be given by troff are divided into the following categories. The name associated with each warning is used by the @samp{-w} and @samp{-W} options; the number is used by the @code{warn} request, and by the @code{.warn} register. @table @samp @item char @itemx 1 Non-existent characters. This is enabled by default. @item number @itemx 2 Invalid numeric expressions. This is enabled by default. @item break @itemx 4 In fill mode, lines which could not be broken so that their length was less than the line length. This is enabled by default. @item delim @itemx 8 Missing or mismatched closing delimiters. @item el @itemx 16 Use of the @code{el} request with no matching @code{ie} request. @xref{if-else}, for more information. @item scale @itemx 32 Meaningless scaling indicators. @item range @itemx 64 Out of range arguments. @item syntax @itemx 128 Dubious syntax in numeric expressions. @item di @itemx 256 @findex di @findex da Use of @code{di} or @code{da} without an argument when there is no current diversion. @item mac @itemx 512 Use of undefined strings, macros and diversions. When an undefined string, macro or diversion is used, that string is automatically defined as empty. So, in most cases, at most one warning will be given for each name. @item reg @itemx 1024 Use of undefined number registers. When an undefined number register is used, that register is automatically defined to have a value of 0. a definition is automatically made with a value of 0. So, in most cases, at most one warning will be given for use of a particular name. @item tab @itemx 2048 Use of a tab character where a number was expected. @item right-brace @itemx 4096 @findex \@} Use of @code{\@}} where a number was expected. @item missing @itemx 8192 Requests that are missing non-optional arguments. @item input @itemx 16384 Illegal input characters. @item escape @itemx 32768 Unrecognized escape sequences. When an unrecognized escape sequence is encountered, the escape character is ignored. @item space @itemx 65536 Missing space between a request or macro and its argument. This warning will be given when an undefined name longer than two characters is encountered, and the first two characters of the name make a defined name. The request or macro will not be invoked. When this warning is given, no macro is automatically defined. This is enabled by default. This warning will never occur in compatibility mode. @item font @itemx 131072 Non-existent fonts. This is enabled by default. @item all All warnings except @samp{di}, @samp{mac} and @samp{reg}. It is intended that this covers all warnings that are useful with traditional macro packages. @item w All warnings. @end table @node Implementation Differences, Summary, Debugging, Programming Tutorial @section Implementation Differences @cindex implementation differences @cindex differences in implementation GNU troff has a number of features which cause incompatibilites with documents written with old versions of troff. Long names cause some incompatibilities. @sc{Unix} troff will interpret @example .dsabcd @end example @findex \* @findex \n @findex cp @vindex .C as defining a string @samp{ab} with contents @samp{cd}. Normally, GNU troff will interpret this as a call of a macro named @code{dsabcd}. Also @sc{Unix} troff will interpret @code{\*[} or @code{\n[} as references to a string or number register called @samp{[}. In GNU troff, however, this will normally be interpreted as the start of a long name. In compatibility mode GNU troff will interpret these things in the traditional way. In compatibility mode, however, long names are not recognised. Compatibility mode can be turned on with the @samp{-C} command line option, and turned on or off with the @code{cp} request. The number register @code{.C} is 1 if compatibility mode is on, 0 otherwise. @findex \A GNU troff does not allow the use of the escape sequences @samp{\| \^ \& \@} \@{ \@key{SP} \' \` \- \_ \! \% \c} in names of strings, macros, diversions, number registers, fonts or environments; @sc{Unix} troff does. The @code{\A} escape sequence may be helpful in avoiding use of these escape sequences in names. @cindex fractional point sizes @cindex point sizes, fractional @findex ps Fractional pointsizes cause one noteworthy incompatibility. In @sc{Unix} troff the @code{ps} request ignores scale indicators and so @example .ps 10u @end example will set the pointsize to 10 points, whereas in GNU troff it will set the pointsize to 10 scaled points. @xref{Fractional Type Sizes}, for more information. @findex bd @findex cs @findex tkf @findex tr @findex fp In GNU troff there is a fundamental difference between unformatted, input characters, and formatted, output characters. Everything that affects how an output character will be output is stored with the character; once an output character has been constructed it is unaffected by any subsequent requests that are executed, including @code{bd}, @code{cs}, @code{tkf}, @code{tr}, or @code{fp} requests. Normally output characters are constructed from input characters at the moment immediately before the character is added to the current output line. Macros, diversions and strings are all, in fact, the same type of object; they contain lists of input characters and output characters in any combination. An output character does not behave like an input character for the purposes of macro processing; it does not inherit any of the special properties that the input character from which it was constructed might have had. For example, @example .di x \\\\ .br .di .x @end example @findex \e @findex \! @findex \? will print @samp{\\} in GNU troff; each pair of input backslashes is turned into one output backslash and the resulting output backslashes are not interpreted as escape characters when they are reread. @sc{Unix} troff would interpret them as escape characters when they were reread and would end up printing one @samp{\}. The correct way to obtain a printable backslash is to use the @code{\e} escape sequence: this will always print a single instance of the current escape character, regardless of whether or not it is used in a diversion; it will also work in both GNU troff and @sc{Unix} troff. If you wish for some reason to store in a diversion an escape sequence that will be interpreted when the diversion is reread, you can either use the traditional @code{\!} transparent output facility, or, if this is unsuitable, the new @code{\?} escape sequence. @xref{Diversions}, for more information. @node Summary, , Implementation Differences, Programming Tutorial @section Summary @cindex summary @node geqn, gtbl, Programming Tutorial, Top @chapter @code{geqn} @cindex @code{eqn} @cindex @code{geqn} @menu * Invoking geqn:: @end menu @node Invoking geqn, , geqn, geqn @section Invoking @code{geqn} @cindex invoking @code{geqn} @cindex @code{geqn}, invoking @node gtbl, gpic, geqn, Top @chapter @code{gtbl} @cindex @code{tbl} @cindex @code{gtbl} @menu * Invoking gtbl:: @end menu @node Invoking gtbl, , gtbl, gtbl @section Invoking @code{gtbl} @cindex invoking @code{gtbl} @cindex @code{gtbl}, invoking @node gpic, grap, gtbl, Top @chapter @code{gpic} @cindex @code{pic} @cindex @code{gpic} @menu * Invoking gpic:: @end menu @node Invoking gpic, , gpic, gpic @section Invoking @code{gpic} @cindex invoking @code{gpic} @cindex @code{gpic}, invoking @node grap, grefer, gpic, Top @chapter @code{grap} @cindex @code{grap} @node grefer, gsoelim, grap, Top @chapter @code{grefer} @cindex @code{refer} @cindex @code{grefer} @menu * Invoking grefer:: @end menu @node Invoking grefer, , grefer, grefer @section Invoking @code{grefer} @cindex invoking @code{grefer} @cindex @code{grefer}, invoking @node gsoelim, Devices, grefer, Top @chapter @code{gsoelim} @cindex @code{soelim} @cindex @code{gsoelim} @menu * Invoking gsoelim:: @end menu @node Invoking gsoelim, , gsoelim, gsoelim @section Invoking @code{gsoelim} @cindex invoking @code{gsoelim} @cindex @code{gsoelim}, invoking @node Devices, File formats, gsoelim, Top @chapter Devices @cindex devices @menu * Special Characters:: * grotty:: * grops:: * grodvi:: * grolj4:: * grohtml:: * gxditview:: @end menu @node Special Characters, grotty, Devices, Devices @section Special Characters @cindex special characters @cindex characters, special @c distribute these through the text @xref{Font Files} @node grotty, grops, Special Characters, Devices @section @code{grotty} @cindex @code{grotty} @menu * Invoking grotty:: @end menu @node Invoking grotty, , grotty, grotty @subsection Invoking @code{grotty} @cindex invoking @code{grotty} @cindex @code{grotty}, invoking @node grops, grodvi, grotty, Devices @section @code{grops} @cindex @code{grops} @menu * Invoking grops:: * Embedding PostScript:: @end menu @node Invoking grops, Embedding PostScript, grops, grops @subsection Invoking @code{grops} @cindex invoking @code{grops} @cindex @code{grops}, invoking @node Embedding PostScript, , Invoking grops, grops @subsection Embedding PostScript @cindex embedding postscript @cindex postscript, embedding @node grodvi, grolj4, grops, Devices @section @code{grodvi} @cindex @code{grodvi} @menu * Invoking grodvi:: @end menu @node Invoking grodvi, , grodvi, grodvi @subsection Invoking @code{grodvi} @cindex invoking @code{grodvi} @cindex @code{grodvi}, invoking @node grolj4, grohtml, grodvi, Devices @section @code{grolj4} @cindex @code{grolj4} @menu * Invoking grolj4:: @end menu @node Invoking grolj4, , grolj4, grolj4 @subsection Invoking @code{grolj4} @cindex invoking @code{grolj4} @cindex @code{grolj4}, invoking @node grohtml, gxditview, grolj4, Devices @section @code{grohtml} @cindex @code{grohtml} @menu * Invoking grohtml:: @end menu @node Invoking grohtml, , grohtml, grohtml @subsection Invoking @code{grohtml} @cindex invoking @code{grohtml} @cindex @code{grohtml}, invoking @node gxditview, , grohtml, Devices @section @code{gxditview} @cindex @code{gxditview} @menu * Invoking gxditview:: @end menu @node Invoking gxditview, , gxditview, gxditview @subsection Invoking @code{gxditview} @cindex invoking @code{gxditview} @cindex @code{gxditview}, invoking @node File formats, Installation, Devices, Top @chapter File formats @cindex file formats @cindex formats, file @menu * gtroff Output:: * Font Files:: @end menu @node gtroff Output, Font Files, File formats, File formats @section @code{gtroff} Output @cindex @code{gtroff} output @cindex output, @code{gtroff} This section describes the format output by GNU troff. The output format used by GNU troff is very similar to that used by @sc{Unix} device-independent troff. The output format is ascii based, as opposed to a binary format (like @TeX{} dvi). The output format is 8 bit clean, thus single characters can have the eighth bit set, as can the names of fonts and special characters. The output format consists of single command characters with attached parameters which are separated from subsequent text by whitespace, or a newline. The names of characters and fonts an be of arbitrary length; drivers should not assume that they will be only two characters long (as device-independent troff did). When a character is to be printed, that character will always be in the current font. Unlike device-independent troff, it is not necessary for drivers to search special fonts to find a character. @table @code @item H@var{n} @item V@var{n} @item h@var{n} @item v@var{n} @item c@var{n} @item C@var{n} @item @var{nn}@var{c} @item t@var{xxx} @var{xxx} is any sequence of characters terminated by a space or a newline; the first character should be printed at the current position, the the current horizontal position should be increased by the width of the first character, and so on for each character. The width of the character is that given in the font file, appropriately scaled for the current point size, and rounded so that it is a multiple of the horizontal resolution. Special characters cannot be printed using this command. This command is only allowed if the @samp{tcommand} line is present in the @file{DESC} file. @item u@var{n} @var{xxx} @pindex DESC This is same as the @code{t} command except that after printing each character, the current horizontal position is increased by the sum of the width of that character and @code{n}. This command is only allowed if the @samp{tcommand} line is present in the @file{DESC} file. @item n@var{a}@var{b} @item p@var{n} @item s@var{n} The argument to the s command is in scaled points (units of points/n, where n is the argument to the sizescale command in the DESC file.) @item f@var{n} @item x @dots{} \n Device control. @item D@var{c} @var{x}@dots{}\n @end table @subsection Device Control The @code{x} command is normally followed by a letter or word indicating the function to perform, followed by white space separated arguments. The first argument can be abreviated to the first letter. @table @code @item x init @item x T @item x res @var{n} @var{h} @var{v} @item x H The argument to the x Height command is also in scaled points. @end table The first three output commands are guaranteed to be: @example x T device x res n h v x init @end example For example, the input @samp{crunchy \fH\s+2frog\s0\fP!?} will produce: @example ... sample output here ... @end example @subsection Drawing Functions The D drawing command has been extended. These extensions will only be used by GNU pic if the -x option is given. @table @code ... @item Df n\n Set the shade of gray to be used for filling solid objects to n; n must be an integer between 0 and 1000, where 0 corresponds solid white and 1000 to solid black, and values in between correspond to intermediate shades of gray. This applies only to solid circles, solid ellipses and solid polygons. By default, a level of 1000 will be used. Whatever color a solid object has, it should completely obscure everything beneath it. A value greater than 1000 or less than 0 can also be used: this means fill with the shade of gray that is currently being used for lines and text. Normally this will be black, but some drivers may provide a way of changing this. @item DC d\n Draw a solid circle with a diameter of d with the leftmost point at the current position. @item DE dx dy\n Draw a solid ellipse with a horizontal diameter of dx and a vertical diameter of dy with the leftmost point at the current position. @item Dp $dx sub 1$ $dy sub 1$ $dx sub 2$ $dy sub 2$ $...$ $dx sub n$ $dy sub n$\n Draw a polygon with, for $i = 1 ,..., n+1$, the i-th vertex at the current position $+ sum from j=1 to i-1 ( dx sub j , dy sub j )$. At the moment, GNU pic only uses this command to generate triangles and rectangles. @item DP $dx sub 1$ $dy sub 1$ $dx sub 2$ $dy sub 2$ $...$ $dx sub n$ $dy sub n$\n Like Dp but draw a solid rather than outlined polygon. @item Dt n\n Set the current line thickness to n machine units. Traditionally @sc{Unix} troff drivers use a line thickness proportional to the current point size; drivers should continue to do this if no Dt command has been given, or if a Dt command has been given with a negative value of n. A zero value of n selects the smallest available line thickness. @end table A difficulty arises in how the current position should be changed after the execution of these commands. This is not of great importance since the code generated by GNU pic does not depend on this. Given a drawing command of the form \D'c $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$ $x sub n$ $y sub n$' where c is not one of c, e, l, a or ~, @sc{Unix} troff will treat each of the $x sub i$ as a horizontal quantity, and each of the $y sub i$ as a vertical quantity and will assume that the width of the drawn object is $sum from i=1 to n x sub i$, and that the height is $sum from i=1 to n y sub i$. (The assumption about the height can be seen by examining the st and sb registers after using such a D command in a \w escape sequence.) This rule also holds for all the original drawing commands with the exception of De. For the sake of compatibility GNU troff also follows this rule, even though it produces an ugly result in the case of the Df, Dt, and, to a lesser extent, DE commands. Thus after executing a D command of the form Dc $x sub 1$ $y sub 1$ $x sub 2$ $y sub 2$ $...$ $x sub n$ $y sub n$\n the current position should be increased by $( sum from i=1 to n x sub i , sum from i=1 to n y sub i )$. @subsection Line Continuation There is a continuation convention which permits the argument to the x X command to contain newlines: when outputting the argument to the x X command, GNU troff will follow each newline in the argument with a + character (as usual, it will terminate the entire argument with a newline); thus if the line after the line containing the x X command starts with +, then the newline ending the line containing the x X command should be treated as part of the argument to the x X command, the + should be ignored, and the part of the line following the + should be treated like the part of the line following the x X command. @node Font Files, , gtroff Output, File formats @section Font Files @cindex font files @cindex files, font The groff font format is roughly a superset of the ditroff font format. Unlike the ditroff font format, there is no associated binary format. The font files for device name are stored in a directory @file{dev@var{name}}. There are two types of file: a device description file called @file{DESC} and for each font @samp{F} a font file called @file{F}. These are text files; there is no associated binary format. @subsection @file{DESC} file format @pindex DESC The @file{DESC} file can contain the following types of line: @table @code @item res @var{n} There are @var{n} machine units per inch. @item hor @var{n} The horizontal resolution is @var{n} machine units. @item vert @var{n} The vertical resolution is @var{n} machine units. @item sizescale @var{n} The scale factor for pointsizes. By default this has a value of 1. One scaled point is equal to one point/@var{n}. The arguments to the @code{unitwidth} and @code{sizes} commands are given in scaled points. @xref{Fractional Type Sizes}, for more information. @item unitwidth @var{n} Quantities in the font files are given in machine units for fonts whose point size is @var{n} scaled points. @item tcommand This means that the postprocessor can handle the @code{t} and @code{u} output commands. @item sizes @var{s1} @var{s2}@dots{}@var{sn} 0 This means that the device has fonts at @var{s1}, @var{s2}, @dots{}@var{sn} scaled points. The list of sizes must be terminated by a 0. Each @var{si} can also be a range of sizes @var{m}-@var{n}. The list can extend over more than one line. @item styles @var{S1 S2@dots{}Sm} The first @var{m} font positions will be associated with styles @var{S1}@dots{}@var{Sm}. @item fonts @var{n} @var{F1 F2 F3@dots{}Fn} Fonts @var{F1@dots{}Fn} will be mounted in the font positions @var{m}+1, @dots{}, @var{m}+@var{n} where @var{m} is the number of styles. This command may extend over more than one line. A font name of 0 will cause no font to be mounted on the corresponding font position. @item family @var{fam} The default font family is @var{fam}. @item charset This line and everything following in the file are ignored. It is allowed for the sake of backwards compatibility. @end table The @code{res}, @code{unitwidth}, @code{fonts} and @code{sizes} lines are compulsory. Other commands are ignored by troff but may be used by postprocessors to store arbitrary information about the device in the @file{DESC} file. @subsection Font file format A font file has two sections. The first section is a sequence of lines each containing a sequence of blank delimited words; the first word in the line is a key, and subsequent words give a value for that key. @table @code @item name @var{F} The name of the font is @var{F}. @item spacewidth @var{n} The normal width of a space is @var{n}. @item slant @var{n} The characters of the font have a slant of @var{n} degrees. (Positive means forward.) @item ligatures @var{lig1} @var{lig2}@dots{}@var{lign} [0] Characters @var{lig1}, @var{lig2}, @dots{}, @var{lign} are ligatures; possible ligatures are ff, fi, fl and ffl. For backwards compatibiliy, the list of ligatures may be terminated with a 0. The list of ligatures may not extend over more than one line. @item special The font is special; this means that when a character is requested that is not present in the current font, it will be searched for in any special fonts that are mounted. @end table Other commands are ignored by troff but may be used by postprocessors to store arbitrary information about the font in the font file. The first section can contain comments which start with the # character and extend to the end of a line. The second section contains one or two subsections. It must contain a @code{charset} subsection and it may also contain a @code{kernpairs} subsection. These subsections can appear in any order. Each subsection starts with a word on a line by itself. The word @code{charset} starts the @code{charset} subsection. The @code{charset} line is followed by a sequence of lines. Each line gives information for one character. A line comprises a number of fields separated by blanks or tabs. The format is @display @var{name} @var{metrics} @var{type} @var{code} @var{comment} @end display @var{name} identifies the character: if @var{name} is a single character @var{c} then it corresponds to the groff input character @var{c}; if it is of the form @samp{\@var{c}} where @var{c} is a single character, then it corresponds to the groff input character @samp{\@var{c}}; otherwise it corresponds to the groff input character @samp{\[@var{name}]} (if it is exactly two characters @var{xx} it can be entered as @samp{\(@var{xx}}.) Groff supports eight bit characters; however some utilities has difficulties with eight bit characters. For this reason, there is a convention that the @var{name} @samp{char@var{n}} is equivalent to the single character whose code is @var{n}. For example, @samp{char163} would be equivalent to the character with @var{code} 163 which is the pounds sterling sign in ISO Latin-1 character set. The name @samp{---} is special and indicates that the character is unnamed; such characters can only be used by means of the @code{\N} escape sequence in troff. The @var{type} field gives the character type: @table @code @item 1 means the character has an descender, for example, p; @item 2 means the character has an ascender, for example, b; @item 3 means the character has both an ascender and a descender, for example, @samp{(}. @end table The @var{code} field gives the code which the postprocessor uses to print the character. The character can also be input to groff using this code by means of the @code{\N} escape sequence. The code can be any integer. If it starts with a 0 it will be interpreted as octal; if it starts with 0x or 0X it will be intepreted as hexdecimal. Anything on the line after the @var{code} field will be ignored. The @var{metrics} field has the form: @smallexample @var{width[,height[,depth[,italic_correction[,left_italic_correction[,subscript_correction]]]]]} @end smallexample There must not be any spaces between these subfields. Missing subfields are assumed to be 0. The subfields are all decimal integers. Since there is no associated binary format, these values are not required to fit into a variable of type @samp{char} as they are in ditroff. The @var{width} subfields gives the width of the character. The @var{height} subfield gives the height of the character (upwards is positive); if a character does not extend above the baseline, it should be given a zero height, rather than a negative height. The @var{depth} subfield gives the depth of the character, that is, the distance below the lowest point below the baseline to which the character extends (downwards is positive); if a character does not extend below above the baseline, it should be given a zero depth, rather than a negative depth. The @var{italic_correction} subfield gives the amount of space that should be added after the character when it is immediately to be followed by a character from a roman font. The @var{left_italic_correction} subfield gives the amount of space that should be added before the character when it is immediately to be preceded by a character from a roman font. The @var{subscript_correction} gives the amount of space that should be added after a character before adding a subscript. This should be less than the italic correction. A line in the @code{charset} section can also have the format @example @var{name} " @end example This indicates that @var{name} is just another name for the character mentioned in the preceding line. The word @code{kernpairs} starts the kernpairs section. This contains a sequence of lines of the form: @display @var{c1 c2 n} @end display This means that when character @var{c1} appears next to character @var{c2} the space between them should be increased by @var{n}. Most entries in kernpairs section will have a negative value for @var{n}. @node Installation, Request Index, File formats, Top @chapter Installation @cindex installation @node Request Index, Register Index, Installation, Top @chapter Request Index @printindex fn @node Register Index, String Index, Request Index, Top @chapter Register Index @printindex vr @node String Index, Macro Index, Register Index, Top @chapter String Index @node Macro Index, Program Index, String Index, Top @chapter Macro Index @node Program Index, Concept Index, Macro Index, Top @chapter Program Index @printindex pg @node Concept Index, , Program Index, Top @chapter Concept Index @printindex cp @summarycontents @contents @bye