'\" t .\" $OpenBSD: sh.1,v 1.5 1998/06/25 19:02:17 millert Exp $ .\"{{{}}} .\"{{{ Notes about man page .\" - use the pseudo-macros .sh( and .sh) to begin and end sh-specific .\" text and .ksh( and .ksh) for ksh specific text. .\" - put i.e., e.g. and etc. in italics .\"}}} .\"{{{ To do .\" todo: Things not covered that should be: .\" - distinguish (POSIX) special built-in's, (POSIX) regular built-in's, .\" and sh/ksh weirdo built-in's (put S,R,X superscripts after command .\" name in built-in commands section?) .\" - need to be consistent about notation for `See section-name', ` .\" See description of foobar command', `See section section-name', etc. .\" - need to use the term `external command' meaning `a command that is .\" executed using execve(2)' (as opposed to a built-in command or .\" function) for more clear description. .\"}}} .\"{{{ Title .TH SH 1 "August 19, 1996" "" "User commands" .\"}}} .\"{{{ Name .SH NAME sh \- Public domain Bourne shell .\"}}} .\"{{{ Synopsis .SH SYNOPSIS .ad l \fBsh\fP [\fB\(+-abCefhikmnprsuvxX\fP] [\fB\(+-o\fP \fIoption\fP] [ [ \fB\-c\fP \fIcommand-string\fP [\fIcommand-name\fP] | \fB\-s\fP | \fIfile\fP ] [\fIargument\fP ...] ] .ad b .\"}}} .\"{{{ Description .SH DESCRIPTION \fBsh\fP is a reimplementation of the Bourne shell, a command interpreter for both interactive and script use. .\"{{{ Shell Startup .SS "Shell Startup" The following options can be specified only on the command line: .IP "\fB\-c\fP \fIcommand-string\fP" the shell executes the command(s) contained in \fIcommand-string\fP .IP \fB\-i\fP interactive mode \(em see below .IP \fB\-l\fP login shell \(em see below interactive mode \(em see below .IP \fB\-s\fP the shell reads commands from standard input; all non-option arguments are positional parameters .IP \fB\-r\fP restricted mode \(em see below .PP In addition to the above, the options described in the \fBset\fP built-in command can also be used on the command line. .PP If neither the \fB\-c\fP nor the \fB\-s\fP options are specified, the first non-option argument specifies the name of a file the shell reads commands from; if there are no non-option arguments, the shell reads commands from standard input. The name of the shell (\fIi.e.\fP, the contents of the \fB$0\fP) parameter is determined as follows: if the \fB\-c\fP option is used and there is a non-option argument, it is used as the name; if commands are being read from a file, the file is used as the name; otherwise the name the shell was called with (\fIi.e.\fP, argv[0]) is used. .PP A shell is \fBinteractive\fP if the \fB\-i\fP option is used or if both standard input and standard error are attached to a tty. An interactive shell has job control enabled (if available), ignores the INT, QUIT and TERM signals, and prints prompts before reading input (see \fBPS1\fP and \fBPS2\fP parameters). For non-interactive shells, the \fBtrackall\fP option is on by default (see \fBset\fP command below). .PP A shell is \fBrestricted\fP if the \fB\-r\fP option is used or if either the basename of the name the shell is invoked with or the \fBSHELL\fP parameter match the pattern *r*sh (\fIe.g.\fP, rsh, rksh, rpdksh, \fIetc.\fP). The following restrictions come into effect after the shell processes any profile and \fB$ENV\fP files: .nr P2 \n(PD .nr PD 0 .IP \ \ \(bu the \fBcd\fP command is disabled .IP \ \ \(bu the \fBSHELL\fP, \fBENV\fP and \fBPATH\fP parameters can't be changed .IP \ \ \(bu command names can't be specified with absolute or relative paths .IP \ \ \(bu the \fB\-p\fP option of the \fBcommand\fP built-in can't be used .IP \ \ \(bu redirections that create files can't be used (\fIi.e.\fP, \fB>\fP, \fB>|\fP, \fB>>\fP, \fB<>\fP) .nr PD \n(P2 .PP A shell is \fBprivileged\fP if the \fB\-p\fP option is used or if the real user-id or group-id does not match the effective user-id or group-id (see \fIgetuid\fP(2), \fIgetgid\fP(2)). A privileged shell does not process $HOME/.profile nor the \fBENV\fP parameter (see below), instead the file /etc/suid_profile is processed. Clearing the privileged option causes the shell to set its effective user-id (group-id) to its real user-id (group-id). .PP If the basename of the name the shell is called with (\fIi.e.\fP, argv[0]) starts with \fB\-\fP or if the \fB\-l\fP option is used, the shell is assumed to be a login shell and the shell reads and executes the contents of \fB/etc/profile\fP and \fB$HOME/.profile\fP if they exist and are readable. .PP If the \fBENV\fP parameter is set when the shell starts (or, in the case of login shells, after any profiles are processed), its value is subjected to parameter, command, arithmetic and tilde substitution and the resulting file (if any) is read and executed. If \fBENV\fP parameter is not set (and not null) and pdksh was compiled with the \fBDEFAULT_ENV\fP macro defined, the file named in that macro is included (after the above mentioned substitutions have been performed). .PP The exit status of the shell is 127 if the command file specified on the command line could not be opened, or non-zero if a fatal syntax error occurred during the execution of a script. In the absence of fatal errors, the exit status is that of the last command executed, or zero, if no command is executed. .\"}}} .\"{{{ Command Syntax .SS "Command Syntax" .\"{{{ words and tokens The shell begins parsing its input by breaking it into \fIword\fPs. Words, which are sequences of characters, are delimited by unquoted \fIwhite-space\fP characters (space, tab and newline) or \fImeta-characters\fP (\fB<\fP, \fB>\fP, \fB|\fP, \fB;\fP, \fB&\fP, \fB(\fP and \fB)\fP). Aside from delimiting words, spaces and tabs are ignored, while newlines usually delimit commands. The meta-characters are used in building the following tokens: \fB<\fP, \fB<&\fP, \fB<<\fP, \fB>\fP, \fB>&\fP, \fB>>\fP, \fIetc.\fP are used to specify redirections (see Input/Output Redirection below); \fB|\fP is used to create pipelines; \fB;\fP is used to separate commands; \fB&\fP is used to create asynchronous pipelines; \fB&&\fP and \fB||\fP are used to specify conditional execution; \fB;;\fP is used in \fBcase\fP statements; and lastly, \fB(\fP .. \fB)\fP are used to create subshells. .PP White-space and meta-characters can be quoted individually using backslash (\fB\e\fP), or in groups using double (\fB"\fP) or single (\fB'\fP) quotes. Note that the following characters are also treated specially by the shell and must be quoted if they are to represent themselves: \fB\e\fP, \fB"\fP, \fB'\fP, \fB#\fP, \fB$\fP, \fB`\fP, \fB~\fP, \fB{\fP, \fB}\fP, \fB*\fP, \fB?\fP and \fB[\fP. The first three of these are the above mentioned quoting characters (see Quoting below); \fB#\fP, if used at the beginning of a word, introduces a comment \(em everything after the \fB#\fP up to the nearest newline is ignored; \fB$\fP is used to introduce parameter, command and arithmetic substitutions (see Substitution below); \fB`\fP introduces an old-style command substitution (see Substitution below); \fB~\fP begins a directory expansion (see Tilde Expansion below); \fB{\fP and \fB}\fP delimit \fIcsh\fP(1) style alternations (see Brace Expansion below); and, finally, \fB*\fP, \fB?\fP and \fB[\fP are used in file name generation (see File Name Patterns below). .\"}}} .\"{{{ simple-command .PP As words and tokens are parsed, the shell builds commands, of which there are two basic types: \fIsimple-commands\fP, typically programs that are executed, and \fIcompound-commands\fP, such as \fBfor\fP and \fBif\fP statements, grouping constructs and function definitions. .PP A simple-command consists of some combination of parameter assignments (see Parameters below), input/output redirections (see Input/Output Redirections below), and command words; the only restriction is that parameter assignments come before any command words. The command words, if any, define the command that is to be executed and its arguments. The command may be a shell built-in command, a function or an \fIexternal command\fP, \fIi.e.\fP, a separate executable file that is located using the \fBPATH\fP parameter (see Command Execution below). Note that all command constructs have an \fIexit status\fP: for external commands, this is related to the status returned by \fIwait\fP(2) (if the command could not be found, the exit status is 127, if it could not be executed, the exit status is 126); the exit status of other command constructs (built-in commands, functions, compound-commands, pipelines, lists, \fIetc.\fP) are all well defined and are described where the construct is described. The exit status of a command consisting only of parameter assignments is that of the last command substitution performed during the parameter assignment or zero if there were no command substitutions. .\"}}} .\"{{{ pipeline .PP Commands can be chained together using the \fB|\fP token to form \fIpipelines\fP, in which the standard output of each command but the last is piped (see \fIpipe\fP(2)) to the standard input of the following command. The exit status of a pipeline is that of its last command. A pipeline may be prefixed by the \fB!\fP reserved word which causes the exit status of the pipeline to be logically complemented: if the original status was 0 the complemented status will be 1, and if the original status was not 0, then the complemented status will be 0. .\"}}} .\"{{{ lists .PP \fILists\fP of commands can be created by separating pipelines by any of the following tokens: \fB&&\fP, \fB||\fP, \fB&\fP, \fB|&\fP and \fB;\fP. The first two are for conditional execution: \fIcmd1\fP \fB&&\fP \fIcmd2\fP executes \fIcmd2\fP only if the exit status of \fIcmd1\fP is zero; \fB||\fP is the opposite \(em \fIcmd2\fP is executed only if the exit status of \fIcmd1\fP is non-zero. \fB&&\fP and \fB||\fP have equal precedence which is higher than that of \fB&\fP, \fB|&\fP and \fB;\fP, which also have equal precedence. The \fB&\fP token causes the preceding command to be executed asynchronously, that is, the shell starts the command, but does not wait for it to complete (the shell does keep track of the status of asynchronous commands \(em see Job Control below). When an asynchronous command is started when job control is disabled (\fIi.e.\fP, in most scripts), the command is started with signals INT and QUIT ignored and with input redirected from /dev/null (however, redirections specified in the asynchronous command have precedence). Note that a command must follow the \fB&&\fP and \fB||\fP operators, while a command need not follow \fB&\fP, \fB|&\fP and \fB;\fP. The exit status of a list is that of the last command executed, with the exception of asynchronous lists, for which the exit status is 0. .\"}}} .\"{{{ compound-commands .PP Compound commands are created using the following reserved words \(em these words are only recognized if they are unquoted and if they are used as the first word of a command (\fIi.e.\fP, they can't be preceded by parameter assignments or redirections): .TS center; lfB lfB lfB lfB lfB . case else function then ! do esac if time [[ done fi in until { elif for select while } .TE \fBNote:\fP Some shells (but not this one) execute control structure commands in a subshell when one or more of their file descriptors are redirected, so any environment changes inside them may fail. To be portable, the \fBexec\fP statement should be used instead to redirect file descriptors before the control structure. .PP In the following compound command descriptions, command lists (denoted as \fIlist\fP) that are followed by reserved words must end with a semi-colon, a newline or a (syntactically correct) reserved word. For example, .RS \fB{ echo foo; echo bar; }\fP .br \fB{ echo foo; echo bar}\fP .br \fB{ { echo foo; echo bar; } }\fP .RE are all valid, but .RS \fB{ echo foo; echo bar }\fP .RE is not. .\"{{{ ( list ) .IP "\fB(\fP \fIlist\fP \fB)\fP" Execute \fIlist\fP in a subshell. There is no implicit way to pass environment changes from a subshell back to its parent. .\"}}} .\"{{{ { list } .IP "\fB{\fP \fIlist\fP \fB}\fP" Compound construct; \fIlist\fP is executed, but not in a subshell. Note that \fB{\fP and \fB}\fP are reserved words, not meta-characters. .\"}}} .\"{{{ case word in [ [ ( ] pattern [ | pattern ] ... ) list ;; ] ... esac .IP "\fBcase\fP \fIword\fP \fBin\fP [ [\fB(\fP] \fIpattern\fP [\fB|\fP \fIpattern\fP] ... \fB)\fP \fIlist\fP \fB;;\fP ] ... \fBesac\fP" The \fBcase\fP statement attempts to match \fIword\fP against the specified \fIpattern\fPs; the \fIlist\fP associated with the first successfully matched pattern is executed. Patterns used in \fBcase\fP statements are the same as those used for file name patterns except that the restrictions regarding \fB\&.\fP and \fB/\fP are dropped. Note that any unquoted space before and after a pattern is stripped; any space with a pattern must be quoted. Both the word and the patterns are subject to parameter, command, and arithmetic substitution as well as tilde substitution. For historical reasons, open and close braces may be used instead of \fBin\fP and \fBesac\fP (\fIe.g.\fP, \fBcase $foo { *) echo bar; }\fP). The exit status of a \fBcase\fP statement is that of the executed \fIlist\fP; if no \fIlist\fP is executed, the exit status is zero. .\"}}} .\"{{{ for name [ in word ... term ] do list done .IP "\fBfor\fP \fIname\fP [ \fBin\fP \fIword\fP ... \fIterm\fP ] \fBdo\fP \fIlist\fP \fBdone\fP" where \fIterm\fP is either a newline or a \fB;\fP. For each \fIword\fP in the specified word list, the parameter \fIname\fP is set to the word and \fIlist\fP is executed. If \fBin\fP is not used to specify a word list, the positional parameters (\fB"$1"\fP, \fB"$2"\fP, \fIetc.\fP) are used instead. For historical reasons, open and close braces may be used instead of \fBdo\fP and \fBdone\fP (\fIe.g.\fP, \fBfor i; { echo $i; }\fP). The exit status of a \fBfor\fP statement is the last exit status of \fIlist\fP; if \fIlist\fP is never executed, the exit status is zero. .\"}}} .\"{{{ if list then list [ elif list then list ] ... [ else list ] fi .IP "\fBif\fP \fIlist\fP \fBthen\fP \fIlist\fP [\fBelif\fP \fIlist\fP \fBthen\fP \fIlist\fP] ... [\fBelse\fP \fIlist\fP] \fBfi\fP" If the exit status of the first \fIlist\fP is zero, the second \fIlist\fP is executed; otherwise the \fIlist\fP following the \fBelif\fP, if any, is executed with similar consequences. If all the lists following the \fBif\fP and \fBelif\fPs fail (\fIi.e.\fP, exit with non-zero status), the \fIlist\fP following the \fBelse\fP is executed. The exit status of an \fBif\fP statement is that of non-conditional \fIlist\fP that is executed; if no non-conditional \fIlist\fP is executed, the exit status is zero. .\"}}} .\"{{{ select name [ in word ... ] do list done .\"}}} .\"{{{ until list do list done .IP "\fBuntil\fP \fIlist\fP \fBdo\fP \fIlist\fP \fBdone\fP" This works like \fBwhile\fP, except that the body is executed only while the exit status of the first \fIlist\fP is non-zero. .\"}}} .\"{{{ while list do list done .IP "\fBwhile\fP \fIlist\fP \fBdo\fP \fIlist\fP \fBdone\fP" A \fBwhile\fP is a prechecked loop. Its body is executed as often as the exit status of the first \fIlist\fP is zero. The exit status of a \fBwhile\fP statement is the last exit status of the \fIlist\fP in the body of the loop; if the body is not executed, the exit status is zero. .\"}}} .\"{{{ function name { list } .IP "\fBfunction\fP \fIname\fP \fB{\fP \fIlist\fP \fB}\fP" Defines the function \fIname\fP. See Functions below. Note that redirections specified after a function definition are performed whenever the function is executed, not when the function definition is executed. .\"}}} .\"{{{ name () command .IP "\fIname\fP \fB()\fP \fIcommand\fP" Mostly the same as \fBfunction\fP. See Functions below. .\"}}} .\"{{{ (( expression )) .\"}}} .\"{{{ [[ expression ]] .\"}}} .\"}}} .\"}}} .\"{{{ Quoting .SS Quoting Quoting is used to prevent the shell from treating characters or words specially. There are three methods of quoting: First, \fB\e\fP quotes the following character, unless it is at the end of a line, in which case both the \fB\e\fP and the newline are stripped. Second, a single quote (\fB'\fP) quotes everything up to the next single quote (this may span lines). Third, a double quote (\fB"\fP) quotes all characters, except \fB$\fP, \fB`\fP and \fB\e\fP, up to the next unquoted double quote. \fB$\fP and \fB`\fP inside double quotes have their usual meaning (\fIi.e.\fP, parameter, command or arithmetic substitution) except no field splitting is carried out on the results of double-quoted substitutions. If a \fB\e\fP inside a double-quoted string is followed by \fB\e\fP, \fB$\fP, \fB`\fP or \fB"\fP, it is replaced by the second character; if it is followed by a newline, both the \fB\e\fP and the newline are stripped; otherwise, both the \fB\e\fP and the character following are unchanged. .PP Note: see POSIX Mode below for a special rule regarding sequences of the form \fB"\fP...\fB`\fP...\fB\e"\fP...\fB`\fP..\fB"\fP. .\"}}} .\"{{{ Aliases .SS "Aliases" There are two types of aliases: normal command aliases and tracked aliases. Command aliases are normally used as a short hand for a long or often used command. The shell expands command aliases (\fIi.e.\fP, substitutes the alias name for its value) when it reads the first word of a command. An expanded alias is re-processed to check for more aliases. If a command alias ends in a space or tab, the following word is also checked for alias expansion. The alias expansion process stops when a word that is not an alias is found, when a quoted word is found or when an alias word that is currently being expanded is found. .PP The following command aliases are defined automatically by the shell: .ft B .RS hash='alias \-t' .br type='whence \-v' .RE .ft P .PP Tracked aliases allow the shell to remember where it found a particular command. The first time the shell does a path search for a command that is marked as a tracked alias, it saves the full path of the command. The next time the command is executed, the shell checks the saved path to see that it is still valid, and if so, avoids repeating the path search. Tracked aliases can be listed and created using \fBalias \-t\fP. Note that changing the \fBPATH\fP parameter clears the saved paths for all tracked aliases. If the \fBtrackall\fP option is set (\fIi.e.\fP, \fBset \-o trackall\fP or \fBset \-h\fP), the shell tracks all commands. This option is set automatically for non-interactive shells. For interactive shells, only the following commands are automatically tracked: \fBcat\fP, \fBcc\fP, \fBchmod\fP, \fBcp\fP, \fBdate\fP, \fBed\fP, \fBemacs\fP, \fBgrep\fP, \fBls\fP, \fBmail\fP, \fBmake\fP, \fBmv\fP, \fBpr\fP, \fBrm\fP, \fBsed\fP, \fBsh\fP, \fBvi\fP and \fBwho\fP. .\"}}} .\"{{{ Substitution .SS "Substitution" The first step the shell takes in executing a simple-command is to perform substitutions on the words of the command. There are three kinds of substitution: parameter, command and arithmetic. Parameter substitutions, which are described in detail in the next section, take the form \fB$name\fP or \fB${\fP...\fB}\fP; command substitutions take the form \fB$(\fP\fIcommand\fP\fB)\fP or \fB`\fP\fIcommand\fP\fB`\fP; and arithmetic substitutions take the form \fB$((\fP\fIexpression\fP\fB))\fP. .PP If a substitution appears outside of double quotes, the results of the substitution are generally subject to word or field splitting according to the current value of the \fBIFS\fP parameter. The \fBIFS\fP parameter specifies a list of characters which are used to break a string up into several words; any characters from the set space, tab and newline that appear in the IFS characters are called \fIIFS white space\fP. Sequences of one or more IFS white space characters, in combination with zero or one non-IFS white space characters delimit a field. As a special case, leading and trailing IFS white space is stripped (\fIi.e.\fP, no leading or trailing empty field is created by it); leading or trailing non-IFS white space does create an empty field. .PP Example: if \fBIFS\fP is set to `:', and VAR is set to `A:B::D', the substitution for $VAR results in four fields: `A', `B', `' and `D'. Note that if the \fBIFS\fP parameter is set to the null string, no field splitting is done; if the parameter is unset, the default value of space, tab and newline is used. .PP Also, note that the field splitting applies only to immediate result of the substitution. Using the previous example, the substitution for $VAR:E results in the fields: `A', `B', `' and `D:E', not `A', `B', `', `D' and `E'. This behavior is POSIX compliant, but incompatible with some other shell implementations which do field splitting on the word which contained the substitution or use \fBIFS\fP\ as a general whitespace delimiter. .PP The results of substitution are, unless otherwise specified, also subject to brace expansion and file name expansion (see the relevant sections below). .PP A command substitution is replaced by the output generated by the specified command, which is run in a subshell. For \fB$(\fP\fIcommand\fP\fB)\fP substitutions, normal quoting rules are used when \fIcommand\fP is parsed, however, for the \fB`\fP\fIcommand\fP\fB`\fP form, a \fB\e\fP followed by any of \fB$\fP, \fB`\fP or \fB\e\fP is stripped (a \fB\e\fP followed by any other character is unchanged). As a special case in command substitutions, a command of the form \fB<\fP \fIfile\fP is interpreted to mean substitute the contents of \fIfile\fP ($(< foo) has the same effect as $(cat foo), but it is carried out more efficiently because no process is started). .br .\"todo: fix this( $(..) parenthesis counting). NOTE: \fB$(\fP\fIcommand\fP\fB)\fP expressions are currently parsed by finding the matching parenthesis, regardless of quoting. This will hopefully be fixed soon. .PP Arithmetic substitutions are replaced by the value of the specified expression. For example, the command \fBecho $((2+3*4))\fP prints 14. See Arithmetic Expressions for a description of an \fIexpression\fP. .\"}}} .\"{{{ Parameters .SS "Parameters" Parameters are shell variables; they can be assigned values and their values can be accessed using a parameter substitution. A parameter name is either one of the special single punctuation or digit character parameters described below, or a letter followed by zero or more letters or digits (`_' counts as a letter). Parameter substitutions take the form \fB$\fP\fIname\fP or \fB${\fP\fIname\fP\fB}\fP, where \fIname\fP is a parameter name. If substitution is performed on a parameter that is not set, a null string is substituted unless the \fBnounset\fP option (\fBset \-o nounset\fP or \fBset \-u\fP) is set, in which case an error occurs. .PP .\"{{{ parameter assignment Parameters can be assigned values in a number of ways. First, the shell implicitly sets some parameters like \fB#\fP, \fBPWD\fP, etc.; this is the only way the special single character parameters are set. Second, parameters are imported from the shell's environment at startup. Third, parameters can be assigned values on the command line, for example, `\fBFOO=bar\fP' sets the parameter FOO to bar; multiple parameter assignments can be given on a single command line and they can be followed by a simple-command, in which case the assignments are in effect only for the duration of the command (such assignments are also exported, see below for implications of this). Note that both the parameter name and the \fB=\fP must be unquoted for the shell to recognize a parameter assignment. The fourth way of setting a parameter is with the \fBexport\fP, \fBreadonly\fP and \fBtypeset\fP commands; see their descriptions in the Command Execution section. Fifth, \fBfor\fP and \fBselect\fP loops set parameters as well as the \fBgetopts\fP, \fBread\fP and \fBset \-A\fP commands. Lastly, parameters can be assigned values using assignment operators inside arithmetic expressions (see Arithmetic Expressions below) or using the \fB${\fP\fIname\fP\fB=\fP\fIvalue\fP\fB}\fP form of parameter substitution (see below). .\"}}} .PP .\"{{{ environment Parameters with the export attribute (set using the \fBexport\fP or \fBtypeset \-x\fP commands, or by parameter assignments followed by simple commands) are put in the environment (see \fIenviron\fP(5)) of commands run by the shell as \fIname\fP\fB=\fP\fIvalue\fP pairs. The order in which parameters appear in the environment of a command is unspecified. When the shell starts up, it extracts parameters and their values from its environment and automatically sets the export attribute for those parameters. .\"}}} .\"{{{ ${name[:][-+=?]word} .PP Modifiers can be applied to the \fB${\fP\fIname\fP\fB}\fP form of parameter substitution: .IP \fB${\fP\fIname\fP\fB:-\fP\fIword\fP\fB}\fP if \fIname\fP is set and not null, it is substituted, otherwise \fIword\fP is substituted. .IP \fB${\fP\fIname\fP\fB:+\fP\fIword\fP\fB}\fP if \fIname\fP is set and not null, \fIword\fP is substituted, otherwise nothing is substituted. .IP \fB${\fP\fIname\fP\fB:=\fP\fIword\fP\fB}\fP if \fIname\fP is set and not null, it is substituted, otherwise it is assigned \fIword\fP and the resulting value of \fIname\fP is substituted. .IP \fB${\fP\fIname\fP\fB:?\fP\fIword\fP\fB}\fP if \fIname\fP is set and not null, it is substituted, otherwise \fIword\fP is printed on standard error (preceded by \fIname\fP:) and an error occurs (normally causing termination of a shell script, function or \&.-script). If word is omitted the string `parameter null or not set' is used instead. .PP In the above modifiers, the \fB:\fP can be omitted, in which case the conditions only depend on \fIname\fP being set (as opposed to set and not null). If \fIword\fP is needed, parameter, command, arithmetic and tilde substitution are performed on it; if \fIword\fP is not needed, it is not evaluated. .\"}}} .PP The following forms of parameter substitution can also be used: .\"{{{ ${#name} .IP \fB${#\fP\fIname\fP\fB}\fP The number of positional parameters if \fIname\fP is \fB*\fP, \fB@\fP or is not specified, or the length of the string value of parameter \fIname\fP. .\"}}} .\"{{{ ${#name[*]}, ${#name[@]} .IP "\fB${#\fP\fIname\fP\fB[*]}\fP, \fB${#\fP\fIname\fP\fB[@]}\fP" The number of elements in the array \fIname\fP. .\"}}} .\"{{{ ${name#pattern}, ${name##pattern} .IP "\fB${\fP\fIname\fP\fB#\fP\fIpattern\fP\fB}\fP, \fB${\fP\fIname\fP\fB##\fP\fIpattern\fP\fB}\fP" If \fIpattern\fP matches the beginning of the value of parameter \fIname\fP, the matched text is deleted from the result of substitution. A single \fB#\fP results in the shortest match, two \fB#\fP's results in the longest match. .\"}}} .\"{{{ ${name%pattern}, ${name%%pattern} .IP "\fB${\fP\fIname\fP\fB%\fP\fIpattern\fP\fB}\fP, \fB${\fP\fIname\fP\fB%%\fP\fIpattern\fP\fB}\fP" Like \fB${\fP..\fB#\fP..\fB}\fP substitution, but it deletes from the end of the value. .\"}}} .\"{{{ special shell parameters .PP The following special parameters are implicitly set by the shell and cannot be set directly using assignments: .\"{{{ ! .IP \fB!\fP Process id of the last background process started. If no background processes have been started, the parameter is not set. .\"}}} .\"{{{ # .IP \fB#\fP The number of positional parameters (\fIi.e.\fP, \fB$1\fP, \fB$2\fP, \fIetc.\fP). .\"}}} .\"{{{ $ .IP \fB$\fP The process ID of the shell, or the PID of the original shell if it is a subshell. .\"}}} .\"{{{ - .IP \fB\-\fP The concatenation of the current single letter options (see \fBset\fP command below for list of options). .\"}}} .\"{{{ ? .IP \fB?\fP The exit status of the last non-asynchronous command executed. If the last command was killed by a signal, \fB$?\fP is set to 128 plus the signal number. .\"}}} .\"{{{ 0 .IP "\fB0\fP" The name the shell was invoked with (\fIi.e.\fP, \fBargv[0]\fP), or the \fBcommand-name\fP if it was invoked with the \fB\-c\fP option and the \fBcommand-name\fP was supplied, or the \fIfile\fP argument, if it was supplied. If the \fBposix\fP option is not set, \fB$0\fP is the name of the current function or script. .\"}}} .\"{{{ 1-9 .IP "\fB1\fP ... \fB9\fP" The first nine positional parameters that were supplied to the shell, function or \fB.\fP-script. Further positional parameters may be accessed using \fB${\fP\fInumber\fP\fB}\fP. .\"}}} .\"{{{ * .IP \fB*\fP All positional parameters (except parameter 0), \fIi.e.\fP, \fB$1 $2 $3\fP.... If used outside of double quotes, parameters are separate words (which are subjected to word splitting); if used within double quotes, parameters are separated by the first character of the \fBIFS\fP parameter (or the empty string if \fBIFS\fP is null). .\"}}} .\"{{{ @ .IP \fB@\fP Same as \fB$*\fP, unless it is used inside double quotes, in which case a separate word is generated for each positional parameter \- if there are no positional parameters, no word is generated ("$@" can be used to access arguments, verbatim, without loosing null arguments or splitting arguments with spaces). .\"}}} .\"}}} .\"{{{ general shell parameters .PP The following parameters are set and/or used by the shell: .\"{{{ CDPATH .IP \fBCDPATH\fP Search path for the \fBcd\fP built-in command. Works the same way as \fBPATH\fP for those directories not beginning with \fB/\fP in \fBcd\fP commands. Note that if CDPATH is set and does not contain \fB.\fP nor an empty path, the current directory is not searched. Also, the \fBcd\fP built-in command will display the resulting directory when a match is found in any search path other than the than the empty path. .\"}}} .\"{{{ COLUMNS .IP \fBCOLUMNS\fP Set to the number of columns on the terminal or window. Currently set to the \fBcols\fP value as reported by \fIstty\fP(1) if that value is non-zero. This parameter is used by the interactive line editing modes, and by \fBselect\fP, \fBset \-o\fP and \fBkill \-l\fP commands to format information in columns. .\"}}} .\"{{{ EDITOR .\"}}} .\"{{{ ENV .IP \fBENV\fP If this parameter is found to be set after any profile files are executed, the expanded value is used as a shell start-up file. It typically contains function and alias definitions. .\"}}} .\"{{{ ERRNO .IP \fBERRNO\fP Integer value of the shell's errno variable \(em indicates the reason the last system call failed. .\" todo: ERRNO variable .sp Not implemented yet. .\"}}} .\"{{{ EXECSHELL .IP \fBEXECSHELL\fP If set, this parameter is assumed to contain the shell that is to be used to execute commands that \fIexecve\fP(2) fails to execute and which do not start with a `\fB#!\fP \fIshell\fP' sequence. .\"}}} .\"{{{ FCEDIT .IP \fBFCEDIT\fP The editor used by the \fBfc\fP command (see below). .\"}}} .\"{{{ FPATH .IP \fBFPATH\fP Like \fBPATH\fP, but used when an undefined function is executed to locate the file defining the function. It is also searched when a command can't be found using \fBPATH\fP. See Functions below for more information. .\"}}} .\"{{{ HISTFILE .\"}}} .\"{{{ HISTSIZE .\"}}} .\"{{{ HOME .IP \fBHOME\fP The default directory for the \fBcd\fP command and the value substituted for an unqualified \fB~\fP (see Tilde Expansion below). .\"}}} .\"{{{ IFS .IP \fBIFS\fP Internal field separator, used during substitution and by the \fBread\fP command, to split values into distinct arguments; normally set to space, tab and newline. See Substitution above for details. .br \fBNote:\fP this parameter is not imported from the environment when the shell is started. .\"}}} .\"{{{ KSH_VERSION .\"}}} .\"{{{ SH_VERSION .IP \fBSH_VERSION\fP The version of shell and the date the version was created (readonly). .\"}}} .\"{{{ LINENO .IP \fBLINENO\fP The line number of the function or shell script that is currently being executed. .\" todo: LINENO variable .sp Not implemented yet. .\"}}} .\"{{{ LINES .IP \fBLINES\fP Set to the number of lines on the terminal or window. .\"Currently set to the \fBrows\fP value as reported by \fIstty\fP(1) if that .\"value is non-zero. .\" todo: LINES variable .sp Not implemented yet. .\"}}} .\"{{{ MAIL .\"}}} .\"{{{ MAILCHECK .\"}}} .\"{{{ MAILPATH .\"}}} .\"{{{ OLDPWD .IP \fBOLDPWD\fP The previous working directory. Unset if \fBcd\fP has not successfully changed directories since the shell started, or if the shell doesn't know where it is. .\"}}} .\"{{{ OPTARG .IP \fBOPTARG\fP When using \fBgetopts\fP, it contains the argument for a parsed option, if it requires one. .\"}}} .\"{{{ OPTIND .IP \fBOPTIND\fP The index of the last argument processed when using \fBgetopts\fP. Assigning 1 to this parameter causes \fBgetopts\fP to process arguments from the beginning the next time it is invoked. .\"}}} .\"{{{ PATH .IP \fBPATH\fP A colon separated list of directories that are searched when looking for commands and \fB.\fP'd files. An empty string resulting from a leading or trailing colon, or two adjacent colons is treated as a `.', the current directory. .\"}}} .\"{{{ POSIXLY_CORRECT .IP \fBPOSIXLY_CORRECT\fP If set, this parameter causes the \fBposix\fP option to be enabled. See POSIX Mode below. .\"}}} .\"{{{ PPID .IP \fBPPID\fP The process ID of the shell's parent (readonly). .\"}}} .\"{{{ PS1 .IP \fBPS1\fP \fBPS1\fP is the primary prompt for interactive shells. The prompt is printed verbatim (\fIi.e.\fP, no substitutions are done). Default is `\fB$\ \fP' for non-root users, `\fB#\ \fP' for root.. .\"}}} .\"{{{ PS2 .IP \fBPS2\fP Secondary prompt string, by default `\fB>\fP ', used when more input is needed to complete a command. .\"}}} .\"{{{ PS3 .\"}}} .\"{{{ PS4 .IP \fBPS4\fP Used to prefix commands that are printed during execution tracing (see \fBset \-x\fP command below). The prompt is printed verbatim (\fIi.e.\fP, no substitutions are done). Default is `\fB+\ \fP'. .\"}}} .\"{{{ PWD .IP \fBPWD\fP The current working directory. Maybe unset or null if shell doesn't know where it is. .\"}}} .\"{{{ RANDOM .\"}}} .\"{{{ REPLY .IP \fBREPLY\fP Default parameter for the \fBread\fP command if no names are given. Also used in \fBselect\fP loops to store the value that is read from standard input. .\"}}} .\"{{{ SECONDS .\"}}} .\"{{{ TMOUT .\"}}} .\"{{{ TMPDIR .IP \fBTMPDIR\fP The directory shell temporary files are created in. If this parameter is not set, or does not contain the absolute path of a writable directory, temporary files are created in \fB/tmp\fP. .\"}}} .\"{{{ VISUAL .\"}}} .\"}}} .\"}}} .\"{{{ Tilde Expansion .SS "Tilde Expansion" Tilde expansion, which is done in parallel with parameter substitution, is done on words starting with an unquoted \fB~\fP. The characters following the tilde, up to the first \fB/\fP, if any, are assumed to be a login name. If the login name is empty, \fB+\fP or \fB\-\fP, the value of the \fBHOME\fP, \fBPWD\fP, or \fBOLDPWD\fP parameter is substituted, respectively. Otherwise, the password file is searched for the login name, and the tilde expression is substituted with the user's home directory. If the login name is not found in the password file or if any quoting or parameter substitution occurs in the login name, no substitution is performed. .PP In parameter assignments (those preceding a simple-command or those occurring in the arguments of \fBalias\fP, \fBexport\fP, \fBreadonly\fP, and \fBtypeset\fP), tilde expansion is done after any unquoted colon (\fB:\fP), and login names are also delimited by colons. .PP The home directory of previously expanded login names are cached and re-used. The \fBalias \-d\fP command may be used to list, change and add to this cache (\fIe.g.\fP, `alias \-d fac=/usr/local/facilities; cd ~fac/bin'). .\"}}} .\"{{{ Brace Expansion .\"}}} .\"{{{ File Name Patterns .SS "File Name Patterns" .PP A file name pattern is a word containing one or more unquoted \fB?\fP or \fB*\fP characters or \fB[\fP..\fB]\fP sequences. Once brace expansion has been performed, the shell replaces file name patterns with the sorted names of all the files that match the pattern (if no files match, the word is left unchanged). The pattern elements have the following meaning: .IP \fB?\fP matches any single character. .IP \fB*\fP matches any sequence of characters. .IP \fB[\fP..\fB]\fP matches any of the characters inside the brackets. Ranges of characters can be specified by separating two characters by a \fB\-\fP, \fIe.g.\fP, \fB[a0\-9]\fP matches the letter \fBa\fP or any digit. In order to represent itself, a \fB\-\fP must either be quoted or the first or last character in the character list. Similarly, a \fB]\fP must be quoted or the first character in the list if it is represent itself instead of the end of the list. Also, a \fB!\fP appearing at the start of the list has special meaning (see below), so to represent itself it must be quoted or appear later in the list. .IP \fB[!\fP..\fB]\fP like \fB[\fP..\fB]\fP, except it matches any character not inside the brackets. .PP Note that pdksh currently never matches \fB.\fP and \fB..\fP, but the original ksh, Bourne sh and bash do, so this may have to change (too bad). .PP Note that none of the above pattern elements match either a period (\fB.\fP) at the start of a file name or a slash (\fB/\fP), even if they are explicitly used in a \fB[\fP..\fB]\fP sequence; also, the names \fB.\fP and \fB..\fP are never matched, even by the pattern \fB.*\fP. .PP If the \fBmarkdirs\fP option is set, any directories that result from file name generation are marked with a trailing \fB/\fP. .PP .\" todo: implement this ([[:alpha:]], \fIetc.\fP) The POSIX character classes (\fIi.e.\fP, \fB[:\fP\fIclass-name\fP\fB:]\fP inside a \fB[\fP..\fB]\fP expression) are not yet implemented. .\"}}} .\"{{{ Input/Output Redirection .SS "Input/Output Redirection" When a command is executed, its standard input, standard output and standard error (file descriptors 0, 1 and 2, respectively) are normally inherited from the shell. Three exceptions to this are commands in pipelines, for which standard input and/or standard output are those set up by the pipeline, asynchronous commands created when job control is disabled, for which standard input is initially set to be from \fB/dev/null\fP, and commands for which any of the following redirections have been specified: .IP "\fB>\fP \fIfile\fP" standard output is redirected to \fIfile\fP. If \fIfile\fP does not exist, it is created; if it does exist, is a regular file and the \fBnoclobber\fP option is set, an error occurs, otherwise the file is truncated. Note that this means the command \fIcmd < foo > foo\fP will open \fIfoo\fP for reading and then truncate it when it opens it for writing, before \fIcmd\fP gets a chance to actually read \fIfoo\fP. .IP "\fB>|\fP \fIfile\fP" same as \fB>\fP, except the file is truncated, even if the \fBnoclobber\fP option is set. .IP "\fB>>\fP \fIfile\fP" same as \fB>\fP, except the file an existing file is appended to instead of being truncated. Also, the file is opened in append mode, so writes always go to the end of the file (see \fIopen\fP(2)). .IP "\fB<\fP \fIfile\fP" standard input is redirected from \fIfile\fP, which is opened for reading. .IP "\fB<>\fP \fIfile\fP" same as \fB<\fP, except the file is opened for reading and writing. .IP "\fB<<\fP \fImarker\fP" after reading the command line containing this kind of redirection (called a here document), the shell copies lines from the command source into a temporary file until a line matching \fImarker\fP is read. When the command is executed, standard input is redirected from the temporary file. If \fImarker\fP contains no quoted characters, the contents of the temporary file are processed as if enclosed in double quotes each time the command is executed, so parameter, command and arithmetic substitutions are performed, along with backslash (\fB\e\fP) escapes for \fB$\fP, \fB`\fP, \fB\e\fP and \fB\enewline\fP. If multiple here documents are used on the same command line, they are saved in order. .IP "\fB<<-\fP \fImarker\fP" same as \fB<<\fP, except leading tabs are stripped from lines in the here document. .IP "\fB<&\fP \fIfd\fP" standard input is duplicated from file descriptor \fIfd\fP. \fIfd\fP can be a single digit, indicating the number of an existing file descriptor, the letter \fBp\fP, indicating the file descriptor associated with the output of the current co-process, or the character \fB\-\fP, indicating standard input is to be closed. .IP "\fB>&\fP \fIfd\fP" same as \fB<&\fP, except the operation is done on standard output. .PP In any of the above redirections, the file descriptor that is redirected (\fIi.e.\fP, standard input or standard output) can be explicitly given by preceding the redirection with a single digit. Parameter, command and arithmetic substitutions, tilde substitutions and file name generation are all performed on the \fIfile\fP, \fImarker\fP and \fIfd\fP arguments of redirections. Note however, that the results of any file name generation are only used if a single file is matched; if multiple files match, the word with the unexpanded file name generation characters is used. Note that in restricted shells, redirections which can create files cannot be used. .PP For simple-commands, redirections may appear anywhere in the command, for compound-commands (\fBif\fP statements, \fIetc.\fP), any redirections must appear at the end. Redirections are processed after pipelines are created and in the order they are given, so .RS \fBcat /foo/bar 2>&1 > /dev/null | cat \-n\fP .RE will print an error with a line number prepended to it. .\"}}} .\"{{{ Arithmetic Expressions .SS "Arithmetic Expressions" Integer arithmetic expressions can be used inside \fB$((\fP..\fB))\fP expressions, inside array references (\fIe.g.\fP, \fIname\fP\fB[\fP\fIexpr\fP\fB]\fP), as numeric arguments to the \fBtest\fP command, and as the value of an assignment to an integer parameter. .PP Expression may contain alpha-numeric parameter identifiers, array references, and integer constants and may be combined with the following C operators (listed and grouped in increasing order of precedence). .TP Unary operators: \fB+ \- ! ~ ++ --\fP .TP Binary operators: \fB,\fP .br \fB= *= /= %= += \-= <<= >>= &= ^= |=\fP .br \fB||\fP .br \fB&&\fP .br \fB|\fP .br \fB^\fP .br \fB&\fP .br \fB== !=\fP .br \fB< <= >= >\fP .br \fB<< >>\fP .br \fB+ \-\fP .br \fB* / %\fP .TP Ternary operator: \fB?:\fP (precedence is immediately higher than assignment) .TP Grouping operators: \fB( )\fP .PP Integer constants may be specified with arbitrary bases using the notation \fIbase\fP\fB#\fP\fInumber\fP, where \fIbase\fP is a decimal integer specifying the base, and \fInumber\fP is a number in the specified base. .LP The operators are evaluated as follows: .RS .IP "unary \fB+\fP" result is the argument (included for completeness). .IP "unary \fB\-\fP" negation. .IP "\fB!\fP" logical not; the result is 1 if argument is zero, 0 if not. .IP "\fB~\fP" arithmetic (bit-wise) not. .IP "\fB++\fP" increment; must be applied to a parameter (not a literal or other expression) - the parameter is incremented by 1. When used as a prefix operator, the result is the incremented value of the parameter, when used as a postfix operator, the result is the original value of the parameter. .IP "\fB++\fP" similar to \fB++\fP, except the paramter is decremented by 1. .IP "\fB,\fP" seperates two arithmetic expressions; the left hand side is evaluated first, then the right. The result is value of the expression on the right hand side. .IP "\fB=\fP" assignment; variable on the left is set to the value on the right. .IP "\fB*= /= %= += \-= <<= >>= &= ^= |=\fP" assignment operators; \fI \fP\fB=\fP \fI\fP is the same as \fI\fP \fB=\fP \fI \fP \fB(\fP \fI\fP \fB)\fP. .IP "\fB||\fP" logical or; the result is 1 if either argument is non-zero, 0 if not. The right argument is evaluated only if the left argument is zero. .IP "\fB&&\fP" logical and; the result is 1 if both arguments are non-zero, 0 if not. The right argument is evaluated only if the left argument is non-zero. .IP "\fB|\fP" arithmetic (bit-wise) or. .IP "\fB^\fP" arithmetic (bit-wise) exclusive-or. .IP "\fB&\fP" arithmetic (bit-wise) and. .IP "\fB==\fP" equal; the result is 1 if both arguments are equal, 0 if not. .IP "\fB!=\fP" not equal; the result is 0 if both arguments are equal, 1 if not. .IP "\fB<\fP" less than; the result is 1 if the left argument is less than the right, 0 if not. .IP "\fB<= >= >\fP" less than or equal, greater than or equal, greater than. See <. .IP "\fB<< >>\fP" shift left (right); the result is the left argument with its bits shifted left (right) by the amount given in the right argument. .IP "\fB+ - * /\fP" addition, subtraction, multiplication, and division. .IP "\fB%\fP" remainder; the result is the remainder of the division of the left argument by the right. The sign of the result is unspecified if either argument is negative. .IP "\fI\fP \fB?\fP \fI\fP \fB:\fP \fI\fP" if \fI\fP is non-zero, the result is \fI\fP, otherwise \fI\fP. .RE .\"}}} .\"{{{ Co-Processes .\"}}} .\"{{{ Functions .SS "Functions" Functions are defined using either Korn shell \fBfunction\fP \fIname\fP syntax or the Bourne/POSIX shell \fIname\fP\fB()\fP syntax (see below for the difference between the two forms). Functions are like \fB.\fP-scripts in that they are executed in the current environment, however, unlike \fB.\fP-scripts, shell arguments (\fIi.e.\fP, positional parameters, \fB$1\fP, \fIetc.\fP) are never visible inside them. When the shell is determining the location of a command, functions are searched after special built-in commands, and before regular and non-regular built-ins, and before the \fBPATH\fP is searched. .PP An existing function may be deleted using \fBunset \-f\fP \fIfunction-name\fP. A list of functions can be obtained using \fBtypeset +f\fP and the function definitions can be listed using \fBtypeset \-f\fP. \fBautoload\fP (which is an alias for \fBtypeset \-fu\fP) may be used to create undefined functions; when an undefined function is executed, the shell searches the path specified in the \fBFPATH\fP parameter for a file with the same name as the function, which, if found is read and executed. If after executing the file, the named function is found to be defined, the function is executed, otherwise, the normal command search is continued (\fIi.e.\fP, the shell searches the regular built-in command table and \fBPATH\fP). Note that if a command is not found using \fBPATH\fP, an attempt is made to autoload a function using \fBFPATH\fP (this is an undocumented feature of the original Korn shell). .PP Functions can have two attributes, trace and export, which can be set with \fBtypeset \-ft\fP and \fBtypeset \-fx\fP, respectively. When a traced function is executed, the shell's \fBxtrace\fP option is turned on for the functions duration, otherwise the \fBxtrace\fP option is turned off. The export attribute of functions is currently not used. In the original Korn shell, exported functions are visible to shell scripts that are executed. .PP Since functions are executed in the current shell environment, parameter assignments made inside functions are visible after the function completes. If this is not the desired effect, the \fBtypeset\fP command can be used inside a function to create a local parameter. Note that special parameters (\fIe.g.\fP, \fB$$\fP, \fB$!\fP) can't be scoped in this way. .PP The exit status of a function is that of the last command executed in the function. A function can be made to finish immediately using the \fBreturn\fP command; this may also be used to explicitly specify the exit status. .PP Functions defined with the \fBfunction\fP reserved word are treated differently in the following ways from functions defined with the \fB()\fP notation: .nr P2 \n(PD .nr PD 0 .IP \ \ \(bu the \fB$0\fP parameter is set to the name of the function (Bourne-style functions leave \fB$0\fP untouched). .IP \ \ \(bu parameter assignments preceeding function calls are not kept in the shell environment (executing Bourne-style functions will keep assignments). .IP \ \ \(bu \fBOPTIND\fP is saved/reset and restored on entry and exit from the function so \fBgetopts\fP can be used properly both inside and outside the function (Bourne-style functions leave \fBOPTIND\fP untouched, so using \fBgetopts\fP inside a function interferes with using \fBgetopts\fP outside the function). .nr PD \n(P2 In the future, the following differences will also be added: .nr P2 \n(PD .nr PD 0 .IP \ \ \(bu A separate trap/signal environment will be used during the execution of functions. This will mean that traps set inside a function will not affect the shell's traps and signals that are not ignored in the shell (but may be trapped) will have their default effect in a function. .IP \ \ \(bu The EXIT trap, if set in a function, will be executed after the function returns. .nr PD \n(P2 .\"}}} .\"{{{ POSIX mode .SS "POSIX Mode" The shell is intended to be POSIX compliant, however, in some cases, POSIX behaviour is contrary either to the original Korn shell behaviour or to user convenience. How the shell behaves in these cases is determined by the state of the posix option (\fBset \-o posix\fP) \(em if it is on, the POSIX behaviour is followed, otherwise it is not. The \fBposix\fP option is set automatically when the shell starts up if the environment contains the \fBPOSIXLY_CORRECT\fP parameter. (The shell can also be compiled so that it is in POSIX mode by default, however this is usually not desirable). .PP The following is a list of things that are affected by the state of the \fBposix\fP option: .nr P2 \n(PD .nr PD 0 .IP \ \ \(bu reading of \fB$ENV\fP: if not in posix mode, the \fBENV\fP parameter is not expanded and included when the shell starts. .IP \ \ \(bu \fB\e"\fP inside double quoted \fB`\fP..\fB`\fP command substitutions: in posix mode, the \fB\e"\fP is interpreted when the command is interpreted; in non-posix mode, the backslash is stripped before the command substitution is interpreted. For example, \fBecho "`echo \e"hi\e"`"\fP produces `"hi"' in posix mode, `hi' in non-posix mode. To avoid problems, use the \fB$(...\fP) form of command substitution. .IP \ \ \(bu \fBkill \-l\fP output: in posix mode, signal names are listed one a single line; in non-posix mode, signal numbers, names and descriptions are printed in columns. In future, a new option (\fB\-v\fP perhaps) will be added to distinguish the two behaviours. .IP \ \ \(bu \fBfg\fP exit status: in posix mode, the exit status is 0 if no errors occur; in non-posix mode, the exit status is that of the last foregrounded job. .IP \ \ \(bu \fBgetopts\fP: in posix mode, options must start with a \fB\-\fP; in non-posix mode, options can start with either \fB\-\fP or \fB+\fP. .IP \ \ \(bu brace expansion (also known as alternation): in posix mode, brace expansion is disabled; in non-posix mode, brace expansion enabled. Note that \fBset \-o posix\fP (or setting the \fBPOSIXLY_CORRECT\fP parameter) automatically turns the \fBbraceexpand\fP option off, however it can be explicitly turned on later. .IP \ \ \(bu \fBset \-\fP: in posix mode, this does not clear the \fBverbose\fP or \fBxtrace\fP options; in non-posix mode, it does. .IP \ \ \(bu \fBset\fP exit status: in posix mode, the exit status of set is 0 if there are no errors; in non-posix mode, the exit status is that of any command substitutions performed in generating the set command. For example, `\fBset \-\- `false`; echo $?\fP' prints 0 in posix mode, 1 in non-posix mode. This construct is used in most shell scripts that use the old \fIgetopt\fP(1) command. .IP \ \ \(bu argument expansion of \fBalias\fP, \fBexport\fP, \fBreadonly\fP, and \fBtypeset\fP commands: in posix mode, normal argument expansion done; in non-posix mode, field splitting, file globing, brace expansion and (normal) tilde expansion are turned off, and assignment tilde expansion is turned on. .IP \ \ \(bu signal specification: in posix mode, signals can be specified as digits only if signal numbers match POSIX values (\fIi.e.\fP, HUP=1, INT=2, QUIT=3, ABRT=6, KILL=9, ALRM=14, and TERM=15); in non-posix mode, signals can be always digits. .IP \ \ \(bu alias expansion: in posix mode, alias expansion is only carried out when reading command words; in non-posix mode, alias expansion is carried out on any word following an alias that ended in a space. For example, the following for loop .RS .ft B alias a='for ' i='j' .br a i in 1 2; do echo i=$i j=$j; done .ft P .RE uses parameter \fBi\fP in posix mode, \fBj\fP in non-posix mode. .IP \ \ \(bu test: in posix mode, the expression "\fB-t\fP" (preceded by some number of "\fB!\fP" arguments) is always true as it is a non-zero length string; in non-posix mode, it tests if file descriptor 1 is a tty (\fIi.e.\fP, the \fIfd\fP argument to the \fB-t\fP test may be left out and defaults to 1). .nr PD \n(P2 .\"}}} .\"{{{ Command Execution (built-in commands) .SS "Command Execution" After evaluation of command line arguments, redirections and parameter assignments, the type of command is determined: a special built-in, a function, a regular built-in or the name of a file to execute found using the \fBPATH\fP parameter. The checks are made in the above order. Special built-in commands differ from other commands in that the \fBPATH\fP parameter is not used to find them, an error during their execution can cause a non-interactive shell to exit and parameter assignments that are specified before the command are kept after the command completes. Just to confuse things, if the posix option is turned off (see \fBset\fP command below) some special commands are very special in that no field splitting, file globing, brace expansion nor tilde expansion is preformed on arguments that look like assignments. Regular built-in commands are different only in that the \fBPATH\fP parameter is not used to find them. .PP The original ksh and POSIX differ somewhat in which commands are considered special or regular: .IP "POSIX special commands" .TS lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB . \&. continue exit return trap : eval export set unset break exec readonly shift .TE .IP "Additional ksh special commands" .TS lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB . builtin times typeset .TE .IP "Very special commands (non-posix mode)" .TS lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB . alias readonly set typeset .TE .IP "POSIX regular commands" .TS lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB . alias command fg kill umask bg false getopts read unalias cd fc jobs true wait .TE .IP "Additional ksh regular commands" .TS lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB lw(8m)fB . [ let pwd ulimit echo print test whence .TE .PP In the future, the additional ksh special and regular commands may be treated differently from the POSIX special and regular commands. .PP Once the type of the command has been determined, any command line parameter assignments are performed and exported for the duration of the command. .PP The following describes the special and regular built-in commands: .\"{{{ . file [ arg1 ... ] .IP "\fB\&.\fP \fIfile\fP [\fIarg1\fP ...]" Execute the commands in \fIfile\fP in the current environment. The file is searched for in the directories of \fBPATH\fP. If arguments are given, the positional parameters may be used to access them while \fIfile\fP is being executed. If no arguments are given, the positional parameters are those of the environment the command is used in. .\"}}} .\"{{{ : [ ... ] .IP "\fB:\fP [ ... ]" The null command. Exit status is set to zero. .\"}}} .\"{{{ alias [ -d | +-t [ -r ] ] [+-px] [+-] [name1[=value1] ...] .IP "\fBalias\fP [ \fB\-d\fP | \fB\(+-t\fP [\fB\-r\fP] ] [\fB\(+-px\fP] [\fB\(+-\fP] [\fIname1\fP[\fB=\fP\fIvalue1\fP] ...]" Without arguments, \fBalias\fP lists all aliases. For any name without a value, the existing alias is listed. Any name with a value defines an alias (see Aliases above). .sp When listing aliases, one of two formats is used: normally, aliases are listed as \fIname\fP\fB=\fP\fIvalue\fP, where \fIvalue\fP is quoted; if options were preceded with \fB+\fP or a lone \fB+\fP is given on the command line, only \fIname\fP is printed. In addition, if the \fB\-p\fP option is used, each alias is prefixed with the string "\fBalias\fP\ ". .sp The \fB\-x\fP option sets (\fB+x\fP clears) the export attribute of an alias, or, if no names are given, lists the aliases with the export attribute (exporting an alias has no affect). .sp The \fB\-x\fP option sets the export attribute of an alias, or, if no names are given, lists the aliases with the export attribute (exporting an alias currently has no affect). .sp The \fB\-t\fP option indicates that tracked aliases are to be listed/set (values specified on the command line are ignored for tracked aliases). The \fB\-r\fP option indicates that all tracked aliases are to be reset. .sp The \fB\-d\fP causes directory aliases, which are used in tilde expansion, to be listed or set (see Tilde Expansion above). .\"}}} .\"{{{ bg [job ...] .IP "\fBbg\fP [\fIjob\fP ...]" Resume the specified stopped job(s) in the background. If no jobs are specified, \fB%+\fP is assumed. This command is only available on systems which support job control. See Job Control below for more information. .\"}}} .\"{{{ bind [-l] [-m] [key[=editing-command] ...] .IP "\fBbind\fP [\fB\-m\fP] [\fIkey\fP[\fB=\fP\fIediting-command\fP] ...]" Set or view the current emacs command editing key bindings/macros. See Emacs Interactive Input Line Editing below for a complete description. .\"}}} .\"{{{ break [level] .IP "\fBbreak\fP [\fIlevel\fP]" \fBbreak\fP exits the \fIlevel\fPth inner most for, select, until, or while loop. \fIlevel\fP defaults to 1. .\"}}} .\"{{{ builtin command [arg1 ...] .IP "\fBbuiltin\fP \fIcommand\fP [\fIarg1\fP ...]" Execute the built-in command \fIcommand\fP. .\"}}} .\"{{{ cd [-LP] [dir] .IP "\fBcd\fP [\fB\-LP\fP] [\fIdir\fP]" Set the working directory to \fIdir\fP. If the parameter \fBCDPATH\fP is set, it lists the search path for the directory containing \fIdir\fP. A null path means the current directory. If \fIdir\fP is found in any component of the \fBCDPATH\fP search path other than the null path the name of the new working directory will be written to standard output. If \fIdir\fP is missing, the home directory \fB$HOME\fP is used. If \fIdir\fP is \fB\-\fP, the previous working directory is used (see OLDPWD parameter). If \fB\-L\fP option (logical path) is used or if the \fBphysical\fP option (see \fBset\fP command below) isn't set, references to \fB..\fP in \fIdir\fP are relative to the path used get to the directory. If \fB\-P\fP option (physical path) is used or if the \fBphysical\fP option is set, \fB..\fP is relative to the filesystem directory tree. The \fBPWD\fP and \fBOLDPWD\fP parameters are updated to reflect the current and old wording directory, respectively. .\"}}} .\"{{{ cd [-LP] old new .IP "\fBcd\fP [\fB\-LP\fP] \fIold new\fP" The string \fInew\fP is substituted for \fIold\fP in the current directory, and the shell attempts to change to the new directory. .\"}}} .\"{{{ command [ -pvV ] cmd [arg1 ...] .IP "\fBcommand\fP [\fB\-p\fP] \fIcmd\fP [\fIarg1\fP ...]" \fIcmd\fP is executed exactly as if the \fBcommand\fP had not been specified, with two exceptions: first, \fIcmd\fP cannot be a shell function, and second, special built-in commands lose their specialness (\fIi.e.\fP, redirection and utility errors do not cause the shell to exit, and command assignments are not permanent). If the \fB\-p\fP option is given, a default search path is used instead of the current value of \fBPATH\fP (the actual value of the default path is system dependent: on POSIXish systems, it is the value returned by .ce \fBgetconf CS_PATH\fP ). .sp .\"}}} .\"{{{ continue [levels] .IP "\fBcontinue\fP [\fIlevels\fP]" \fBcontinue\fP jumps to the beginning of the \fIlevel\fPth inner most for, select, until, or while loop. \fIlevel\fP defaults to 1. .\"}}} .\"{{{ echo [-neE] [arg ...] .IP "\fBecho\fP [\fB\-neE\fP] [\fIarg\fP ...]" Prints its arguments (separated by spaces) followed by a newline, to standard out. The newline is suppressed if any of the arguments contain the backslash sequence \fB\ec\fP. See \fBprint\fP command below for a list of other backslash sequences that are recognized. .sp The options are provided for compatibility with BSD shell scripts: \fB\-n\fP suppresses the trailing newline, \fB\-e\fP enables backslash interpretation (a no-op, since this is normally done), and \fB\-E\fP which suppresses backslash interpretation. .\"}}} .\"{{{ eval command ... .IP "\fBeval\fP \fIcommand ...\fP" The arguments are concatenated (with spaces between them) to form a single string which the shell then parses and executes in the current environment. .\"}}} .\"{{{ exec [command [arg ...]] .IP "\fBexec\fP [\fIcommand\fP [\fIarg\fP ...]]" The command is executed without forking, replacing the shell process. .sp If no arguments are given, any IO redirection is permanent and the shell is not replaced. Any file descriptors which are opened or \fIdup\fP(2)-ed in this way are made available to other executed commands (note that the Korn shell differs here: it does not pass on file descriptors greater than 2). .\"}}} .\"{{{ exit [status] .IP "\fBexit\fP [\fIstatus\fP]" The shell exits with the specified exit status. If \fIstatus\fP is not specified, the exit status is the current value of the \fB?\fP parameter. .\"}}} .\"{{{ export [-p] [parameter[=value] ...] .IP "\fBexport\fP [\fB\-p\fP] [\fIparameter\fP[\fB=\fP\fIvalue\fP]] ..." Sets the export attribute of the named parameters. Exported parameters are passed in the environment to executed commands. If values are specified, the named parameters also assigned. .sp If no parameters are specified, the names of all parameters with the export attribute are printed one per line, unless the \fB\-p\fP option is used, in which case \fBexport\fP commands defining all exported parameters, including their values, are printed. .\"}}} .\"{{{ false .IP "\fBfalse\fP" A command that exits with a non-zero status. .\"}}} .\"{{{ fc [-e editor | -l [-n]] [-r] [first [ last ]] .\"}}} .\"{{{ fc [-e - | -s] [-g] [old=new] [prefix] .IP "\fBfc\fP [\fB\-e \-\fP | \fB\-s\fP] [\fB\-g\fP] [\fIold\fP\fB=\fP\fInew\fP] [\fIprefix\fP]" Re-execute the selected command (the previous command by default) after performing the optional substitution of \fIold\fP with \fInew\fP. If \fB\-g\fP is specified, all occurrences of \fIold\fP are replaced with \fInew\fP. This command is usually accessed with the predefined alias \fBr='fc \-e \-'\fP. .\"}}} .\"{{{ fg [job ...] .IP "\fBfg\fP [\fIjob\fP ...]" Resume the specified job(s) in the foreground. If no jobs are specified, \fB%+\fP is assumed. This command is only available on systems which support job control. See Job Control below for more information. .\"}}} .\"{{{ getopts optstring name [arg ...] .IP "\fBgetopts\fP \fIoptstring\fP \fIname\fP [\fIarg\fP ...]" \fBgetopts\fP is used by shell procedures to parse the specified arguments (or positional parameters, if no arguments are given) and to check for legal options. \fIoptstring\fP contains the option letters that \fBgetopts\fP is to recognize. If a letter is followed by a colon, the option is expected to have an argument. Options that do not take arguments may be grouped in a single argument. If an option takes an argument and the option character is not the last character of the argument it is found in, the remainder of the argument is taken to be the option's argument, otherwise, the next argument is the option's argument. .sp Each time \fBgetopts\fP is invoked, it places the next option in the shell parameter \fIname\fP and the index of the next argument to be processed in the shell parameter \fBOPTIND\fP. If the option was introduced with a \fB+\fP, the option placed in \fIname\fP is prefixed with a \fB+\fP. When an option requires an argument, \fBgetopts\fP places it in the shell parameter \fBOPTARG\fP. When an illegal option or a missing option argument is encountered a question mark or a colon is placed in \fIname\fP (indicating an illegal option or missing argument, respectively) and \fBOPTARG\fP is set to the option character that caused the problem. An error message is also printed to standard error if \fIoptstring\fP does not begin with a colon. .sp When the end of the options is encountered, \fBgetopts\fP exits with a non-zero exit status. Options end at the first (non-option argument) argument that does not start with a \-, or when a \fB\-\-\fP argument is encountered. .sp Option parsing can be reset by setting \fBOPTIND\fP to 1 (this is done automatically whenever the shell or a shell procedure is invoked). .sp Warning: Changing the value of the shell parameter \fBOPTIND\fP to a value other than 1, or parsing different sets of arguments without resetting \fBOPTIND\fP may lead to unexpected results. .\"}}} .\"{{{ hash [-r] [name ...] .IP "\fBhash\fP [\fB\-r\fP] [\fIname ...\fP]" Without arguments, any hashed executable command pathnames are listed. The \fB\-r\fP option causes all hashed commands to be removed from the hash table. Each \fIname\fP is searched as if it where a command name and added to the hash table if it is an executable command. .\"}}} .\"{{{ jobs [-lpn] [job ...] .IP "\fBjobs\fP [\fB\-lpn\fP] [\fIjob\fP ...]" Display information about the specified jobs; if no jobs are specified, all jobs are displayed. The \fB\-n\fP option causes information to be displayed only for jobs that have changed state since the last notification. If the \fB\-l\fP option is used, the process-id of each process in a job is also listed. The \fB\-p\fP option causes only the process group of each job to be printed. See Job Control below for the format of \fIjob\fP and the displayed job. .\"}}} .\"{{{ kill [-s signame | -signum | -signame] { job | pid | -pgrp } ... .IP "\fBkill\fP [\fB\-s\fP \fIsigname\fP | \fB\-signum\fP | \fB\-signame\fP ] { \fIjob\fP | \fIpid\fP | \fB\-\fP\fIpgrp\fP } ..." Send the specified signal to the specified jobs, process ids, or process groups. If no signal is specified, the signal TERM is sent. If a job is specified, the signal is sent to the job's process group. See Job Control below for the format of \fIjob\fP. .\"}}} .\"{{{ kill -l [exit-status ...] .IP "\fBkill \-l\fP [\fIexit-status\fP ...]" Print the name of the signal that killed a process which exited with the specified \fIexit-status\fPes. If no arguments are specified, a list of all the signals, their numbers and a short description of them are printed. .\"}}} .\"{{{ let [expression ...] .\"}}} .\"{{{ print [-nprsun | -R [-en]] [argument ...] .IP "\fBprint\fP [\fB\-nprsu\fP\fIn\fP | \fB\-R\fP [\fB\-en\fP]] [\fIargument ...\fP]" \fBPrint\fP prints its arguments on the standard output, separated by spaces, and terminated with a newline. The \fB\-n\fP option suppresses the newline. By default, certain C escapes are translated. These include \eb, \ef, \en, \er, \et, \ev, and \e0### (# is an octal digit, of which there may be 0 to 3). \ec is equivalent to using the \fB\-n\fP option. \e expansion may be inhibited with the \fB\-r\fP option. The \fB\-s\fP option prints to the history file instead of standard output, the \fB\-u\fP option prints to file descriptor \fIn\fP (\fIn\fP defaults to 1 if omitted), and the \fB\-p\fP option prints to the co-process (see Co-Processes above). .sp The \fB\-R\fP option is used to emulate, to some degree, the BSD echo command, which does not process \e sequences unless the \fB\-e\fP option is given. As above, the \fB\-n\fP option suppresses the trailing newline. .\"}}} .\"{{{ pwd [-LP] .IP "\fBpwd\fP [\fB\-LP\fP]" Print the present working directory. If \fB\-L\fP option is used or if the \fBphysical\fP option (see \fBset\fP command below) isn't set, the logical path is printed (\fIi.e.\fP, the path used to \fBcd\fP to the current directory). If \fB\-P\fP option (physical path) is used or if the \fBphysical\fP option is set, the path determined from the filesystem (by following \fB..\fP directories to the root directory) is printed. .\"}}} .\"{{{ read [-prsun] [parameter ...] .IP "\fBread\fP [\fB\-prsu\fP\fIn\fP] [\fIparameter ...\fP]" Reads a line of input from standard input, separate the line into fields using the \fBIFS\fP parameter (see Substitution above), and assign each field to the specified parameters. If there are more parameters than fields, the extra parameters are set to null, or alternatively, if there are more fields than parameters, the last parameter is assigned the remaining fields (inclusive of any separating spaces). If no parameters are specified, the \fBREPLY\fP parameter is used. If the input line ends in a backslash and the \fB\-r\fP option was not used, the backslash and newline are stripped and more input is read. If no input is read, \fBread\fP exits with a non-zero status. .sp The first parameter may have a question mark and a string appended to it, in which case the string is used as a prompt (printed to standard error before any input is read) if the input is a tty (\fIe.g.\fP, \fBread nfoo?'number of foos: '\fP). .sp The \fB\-u\fP\fIn\fP and \fB\-p\fP options cause input to be read from file descriptor \fIn\fP or the current co-process (see Co-Processes above for comments on this), respectively. If the \fB\-s\fP option is used, input is saved to the history file. .\"}}} .\"{{{ readonly [-p] [parameter[=value] ...] .IP "\fBreadonly\fP [\fB\-p\fP] [\fIparameter\fP[\fB=\fP\fIvalue\fP]] ..." Sets the readonly attribute of the named parameters. If values are given, parameters are set to them before setting the attribute. Once a parameter is made readonly, it cannot be unset and its value cannot be changed. .sp If no parameters are specified, the names of all parameters with the readonly attribute are printed one per line, unless the \fB\-p\fP option is used, in which case \fBreadonly\fP commands defining all readonly parameters, including their values, are printed. .\"}}} .\"{{{ return [status] .IP "\fBreturn\fP [\fIstatus\fP]" Returns from a function or \fB.\fP script, with exit status \fIstatus\fP. If no \fIstatus\fP is given, the exit status of the last executed command is used. If used outside of a function or \fB.\fP script, it has the same effect as \fBexit\fP. Note that pdksh treats both profile and \fB$ENV\fP files as \fB.\fP scripts, while the original Korn shell only treats profiles as \fB.\fP scripts. .\"}}} .\"{{{ set [+-abCefhkmnpsuvxX] [+-o [option]] [+-A name] [--] [arg ...] .IP "\fBset\fP [\fB\(+-abCefhkmnpsuvxX\fP] [\fB\(+-o\fP [\fIoption\fP]] [\fB\(+-A\fP \fIname\fP] [\fB\-\-\fP] [\fIarg\fP ...]" The set command can be used to set (\fB\-\fP) or clear (\fB+\fP) shell options, set the positional parameters, or set an array parameter. Options can be changed using the \fB\(+-o\fP \fIoption\fP syntax, where \fIoption\fP is the long name of an option, or using the \fB\(+-\fP\fIletter\fP syntax, where \fIletter\fP is the option's single letter name (not all options have a single letter name). The following table lists both option letters (if they exist) and long names along with a description of what the option does. .sp .TS expand; afB lfB lw(3i). \-A T{ Sets the elements of the array parameter \fIname\fP to \fIarg\fP ...; If \fB\-A\fP is used, the array is reset (\fIi.e.\fP, emptied) first; if \fB+A\fP is used, the first N elements are set (where N is the number of \fIarg\fPs), the rest are left untouched. T} \-a allexport T{ all new parameters are created with the export attribute T} \-b notify T{ Print job notification messages asynchronously, instead of just before the prompt. Only used if job control is enabled (\fB\-m\fP). T} \-C noclobber T{ Prevent \fB>\fP redirection from overwriting existing files (\fB>|\fP must be used to force an overwrite). T} \-e errexit T{ Exit (after executing the \fBERR\fP trap) as soon as an error occurs or a command fails (\fIi.e.\fP, exits with a non-zero status). This does not apply to commands whose exit status is explicitly tested by a shell construct such as \fBif\fP, \fBuntil\fP, \fBwhile\fP, \fB&&\fP or \fB||\fP statements. T} \-f noglob T{ Do not expand file name patterns. T} \-h trackall T{ Create tracked aliases for all executed commands (see Aliases above). On by default for non-interactive shells. T} \-i interactive T{ Enable interactive mode \- this can only be set/unset when the shell is invoked. T} \-k keyword T{ Parameter assignments are recognized anywhere in a command. T} \-l login T{ The shell is a login shell \- this can only be set/unset when the shell is invoked (see Shell Startup above). T} \-m monitor T{ Enable job control (default for interactive shells). T} \-n noexec T{ Do not execute any commands \- useful for checking the syntax of scripts (ignored if interactive). T} \-p privileged T{ Set automatically if, when the shell starts, the read uid or gid does not match the effective uid or gid, respectively. See Shell Startup above for a description of what this means. T} -r restricted T{ Enable restricted mode \(em this option can only be used when the shell is invoked. See Shell Startup above for a description of what this means. T} \-s stdin T{ If used when the shell is invoked, commands are read from standard input. Set automatically if the shell is invoked with no arguments. .sp When \fB\-s\fP is used in the \fBset\fP command, it causes the specified arguments to be sorted before assigning them to the positional parameters (or to array \fIname\fP, if \fB\-A\fP is used). T} \-u nounset T{ Referencing of an unset parameter is treated as an error, unless one of the \fB\-\fP, \fB+\fP or \fB=\fP modifiers is used. T} \-v verbose T{ Write shell input to standard error as it is read. T} \-x xtrace T{ Print commands and parameter assignments when they are executed, preceded by the value of \fBPS4\fP. T} \-X markdirs T{ Mark directories with a trailing \fB/\fP during file name generation. T} bgnice T{ Background jobs are run with lower priority. T} ignoreeof T{ The shell will not exit on when end-of-file is read, \fBexit\fP must be used. T} nohup T{ Do not kill running jobs with a \fBHUP\fP signal when a login shell exists. Currently set by default, but this will change in the future to be compatible with the original Korn shell (which doesn't have this option, but does send the \fBHUP\fP signal). T} nolog T{ No effect \- in the original Korn shell, this prevents function definitions from being stored in the history file. T} physical T{ Causes the \fBcd\fP and \fBpwd\fP commands to use `physical' (\fIi.e.\fP, the filesystem's) \fB..\fP directories instead of `logical' directories (\fIi.e.\fP, the shell handles \fB..\fP, which allows the user to be obliveous of symlink links to directories). Clear by default. Note that setting this option does not effect the current value of the \fBPWD\fP parameter; only the \fBcd\fP command changes \fBPWD\fP. See the \fBcd\fP and \fBpwd\fP commands above for more details. T} posix T{ Enable posix mode. See POSIX Mode above. T} vi T{ Enable vi-like command line editing (interactive shells only). T} viraw T{ No effect \- in the original Korn shell, unless viraw was set, the vi command line mode would let the tty driver do the work until ESC (^[) was entered. pdksh is always in viraw mode. T} vi-esccomplete T{ In vi command line editing, do command / file name completion when escape (^[) is entered in command mode. T} vi-show8 T{ Prefix characters with the eighth bit set with `M-'. If this option is not set, characters in the range 128-160 are printed as is, which may cause problems. T} vi-tabcomplete T{ In vi command line editing, do command / file name completion when tab (^I) is entered in insert mode. T} .TE .sp These options can also be used upon invocation of the shell. The current set of options (with single letter names) can be found in the parameter \fB\-\fP. \fBset -o\fP with no option name will list all the options and whether each is on or off; \fBset +o\fP will print the long names of all options that are currently on. .sp Remaining arguments, if any, are positional parameters and are assigned, in order, to the positional parameters (\fIi.e.\fP, \fB1\fP, \fB2\fP, \fIetc.\fP). If options are ended with \fB\-\-\fP and there are no remaining arguments, all positional parameters are cleared. If no options or arguments are given, then the values of all names are printed. For unknown historical reasons, a lone \fB\-\fP option is treated specially: it clears both the \fB\-x\fP and \fB\-v\fP options. .\"}}} .\"{{{ shift [number] .IP "\fBshift\fP [\fInumber\fP]" The positional parameters \fInumber\fP+1, \fInumber\fP+2 \fIetc.\fP\& are renamed to \fB1\fP, \fB2\fP, \fIetc.\fP \fInumber\fP defaults to 1. .\"}}} .\"{{{ test expression, [ expression ] .IP "\fBtest\fP \fIexpression\fP" .IP "\fB[\fP \fIexpression\fP \fB]\fP" \fBtest\fP evaluates the \fIexpression\fP and returns zero status if true, and 1 status if false and greater than 1 if there was an error. It is normally used as the condition command of \fBif\fP and \fBwhile\fP statements. The following basic expressions are available: .sp .TS afB ltw(2.8i). \fIstr\fP T{ \fIstr\fP has non-zero length. Note that there is the potential for problems if \fIstr\fP turns out to be an operator (\fIe.g.\fP, \fB-r\fP) - it is generally better to use a test like .RS \fB[ X"\fP\fIstr\fP\fB" != X ]\fP .RE instead (double quotes are used in case \fIstr\fP contains spaces or file globing characters). T} \-r \fIfile\fP T{ \fIfile\fP exists and is readable T} \-w \fIfile\fP T{ \fIfile\fP exists and is writable T} \-x \fIfile\fP T{ \fIfile\fP exists and is executable T} \-a \fIfile\fP T{ \fIfile\fP exists T} \-e \fIfile\fP T{ \fIfile\fP exists T} \-f \fIfile\fP T{ \fIfile\fP is a regular file T} \-d \fIfile\fP T{ \fIfile\fP is a directory T} \-c \fIfile\fP T{ \fIfile\fP is a character special device T} \-b \fIfile\fP T{ \fIfile\fP is a block special device T} \-p \fIfile\fP T{ \fIfile\fP is a named pipe T} \-u \fIfile\fP T{ \fIfile\fP's mode has setuid bit set T} \-g \fIfile\fP T{ \fIfile\fP's mode has setgid bit set T} \-k \fIfile\fP T{ \fIfile\fP's mode has sticky bit set T} \-s \fIfile\fP T{ \fIfile\fP is not empty T} \-O \fIfile\fP T{ \fIfile\fP's owner is the shell's effective user-ID T} \-G \fIfile\fP T{ \fIfile\fP's group is the shell's effective group-ID T} \-h \fIfile\fP T{ \fIfile\fP is a symbolic link T} \-H \fIfile\fP T{ \fIfile\fP is a context dependent directory (only useful on HP-UX) T} \-L \fIfile\fP T{ \fIfile\fP is a symbolic link T} \-S \fIfile\fP T{ \fIfile\fP is a socket T} \-o \fIoption\fP T{ shell \fIoption\fP is set (see \fBset\fP command above for list of options). As a non-standard extension, if the option starts with a \fB!\fP, the test is negated; the test always fails if option doesn't exist (thus .RS \fB[ -o \fP\fIfoo\fP \fB-o -o !\fP\fIfoo\fP \fB]\fP .RE returns true if and only if option \fIfoo\fP exists). T} \fIfile\fP \-nt \fIfile\fP T{ first \fIfile\fP is newer than second \fIfile\fP T} \fIfile\fP \-ot \fIfile\fP T{ first \fIfile\fP is older than second \fIfile\fP T} \fIfile\fP \-ef \fIfile\fP T{ first \fIfile\fP is the same file as second \fIfile\fP T} \-t\ [\fIfd\fP] T{ file descriptor is a tty device. If the posix option (\fBset \-o posix\fP, see POSIX Mode above) is not set, \fIfd\fP may be left out, in which case it is taken to be 1 (the behaviour differs due to the special POSIX rules described below). T} \fIstring\fP T{ \fIstring\fP is not empty T} \-z\ \fIstring\fP T{ \fIstring\fP is empty T} \-n\ \fIstring\fP T{ \fIstring\fP is not empty T} \fIstring\fP\ =\ \fIstring\fP T{ strings are equal T} \fIstring\fP\ !=\ \fIstring\fP T{ strings are not equal T} \fInumber\fP\ \-eq\ \fInumber\fP T{ numbers compare equal T} \fInumber\fP\ \-ne\ \fInumber\fP T{ numbers compare not equal T} \fInumber\fP\ \-ge\ \fInumber\fP T{ numbers compare greater than or equal T} \fInumber\fP\ \-gt\ \fInumber\fP T{ numbers compare greater than T} \fInumber\fP\ \-le\ \fInumber\fP T{ numbers compare less than or equal T} \fInumber\fP\ \-lt\ \fInumber\fP T{ numbers compare less than T} .TE .sp The above basic expressions, in which unary operators have precedence over binary operators, may be combined with the following operators (listed in increasing order of precedence): .sp .TS afB l. \fIexpr\fP \-o \fIexpr\fP logical or \fIexpr\fP \-a \fIexpr\fP logical and ! \fIexpr\fP logical not ( \fIexpr\fP ) grouping .TE .sp On operating systems not supporting \fB/dev/fd/\fP\fIn\fP devices (where \fIn\fP is a file descriptor number), the \fBtest\fP command will attempt to fake it for all tests that operate on files (except the \fB-e\fP test). I.e., \fB[ -w /dev/fd/2 ]\fP tests if file descriptor 2 is writable. .sp Note that some special rules are applied (courtesy of POSIX) if the number of arguments to \fBtest\fP or \fB[\fP \&... \fB]\fP is less than five: if leading \fB!\fP arguments can be stripped such that only one argument remains then a string length test is performed (again, even if the argument is a unary operator); if leading \fB!\fP arguments can be stripped such that three arguments remain and the second argument is a binary operator, then the binary operation is performed (even if first argument is a unary operator, including an unstripped \fB!\fP). .sp \fBNote:\fP A common mistake is to use \fBif [ $foo = bar ]\fP which fails if parameter \fBfoo\fP is null or unset, if it has embedded spaces (\fIi.e.\fP, \fBIFS\fP characters), or if it is a unary operator like \fB!\fP or \fB\-n\fP. Use tests like \fBif [ "X$foo" = Xbar ]\fP instead. .\"}}} .\"{{{ times .IP \fBtimes\fP Print the accumulated user and system times used by the shell and by processes which have exited that the shell started. .\"}}} .\"{{{ trap [handler signal ...] .IP "\fBtrap\fP [\fIhandler\fP \fIsignal ...\fP]" Sets trap handler that is to be executed when any of the specified signals are received. \fBHandler\fP is either a null string, indicating the signals are to be ignored, a minus (\fB\-\fP), indicating that the default action is to be taken for the signals (see signal(2 or 3)), or a string containing shell commands to be evaluated and executed at the first opportunity (\fIi.e.\fP, when the current command completes, or before printing the next \fBPS1\fP prompt) after receipt of one of the signals. \fBSignal\fP is the name of a signal (\fIe.g.\fP, PIPE or ALRM) or the number of the signal (see \fBkill \-l\fP command above). There are two special signals: \fBEXIT\fP (also known as \fB0\fP), which is executed when the shell is about to exit, and \fBERR\fP which is executed after an error occurs (an error is something that would cause the shell to exit if the \fB\-e\fP or \fBerrexit\fP option were set \(em see \fBset\fP command above). \fBEXIT\fP handlers are executed in the environment of the last executed command. Note that for non-interactive shells, the trap handler cannot be changed for signals that were ignored when the shell started. .sp With no arguments, \fBtrap\fP lists, as a series of \fBtrap\fP commands, the current state of the traps that have been set since the shell started. .sp .\" todo: add these features (trap DEBUG, trap ERR/EXIT in function) The original Korn shell's \fBDEBUG\fP trap and the handling of \fBERR\fP and \fBEXIT\fP traps in functions are not yet implemented. .\"}}} .\"{{{ true .IP \fBtrue\fP A command that exits with a zero value. .\"}}} .\"{{{ typeset [[+-Ulprtux] [-L[n]] [-R[n]] [-Z[n]] [-i[n]] | -f [-tux]] [name[=value] ...] .IP "\fBtypeset\fP [[\(+-Ulprtux] [\fB\-L\fP[\fIn\fP]] [\fB\-R\fP[\fIn\fP]] [\fB\-Z\fP[\fIn\fP]] [\fB\-i\fP[\fIn\fP]] | \fB\-f\fP [\fB\-tux\fP]] [\fIname\fP[\fB=\fP\fIvalue\fP] ...]" Display or set parameter attributes. With no \fIname\fP arguments, parameter attributes are displayed: if no options arg used, the current attributes of all parameters are printed as typeset commands; if an option is given (or \fB\-\fP with no option letter) all parameters and their values with the specified attributes are printed; if options are introduced with \fB+\fP, parameter values are not printed. .sp If \fIname\fP arguments are given, the attributes of the named parameters are set (\fB\-\fP) or cleared (\fB+\fP). Values for parameters may optionally be specified. If typeset is used inside a function, any newly created parameters are local to the function. .sp When \fB\-f\fP is used, typeset operates on the attributes of functions. As with parameters, if no \fIname\fPs are given, functions are listed with their values (\fIi.e.\fP, definitions) unless options are introduced with \fB+\fP, in which case only the function names are reported. .sp .TS expand; afB lw(4.5i). \-L\fIn\fP T{ Left justify attribute: \fIn\fP specifies the field width. If \fIn\fP is not specified, the current width of a parameter (or the width of its first assigned value) is used. Leading white space (and zeros, if used with the \fB\-Z\fP option) is stripped. If necessary, values are either truncated or space padded to fit the field width. T} \-R\fIn\fP T{ Right justify attribute: \fIn\fP specifies the field width. If \fIn\fP is not specified, the current width of a parameter (or the width of its first assigned value) is used. Trailing white space are stripped. If necessary, values are either stripped of leading characters or space padded to make them fit the field width. T} \-Z\fIn\fP T{ Zero fill attribute: if not combined with \fB\-L\fP, this is the same as \fB\-R\fP, except zero padding is used instead of space padding. T} \-i\fIn\fP T{ integer attribute: \fIn\fP specifies the base to use when displaying the integer (if not specified, the base given in the first assignment is used). Parameters with this attribute may be assigned values containing arithmetic expressions. T} \-U T{ unsigned integer attribute: integers are printed as unsigned values (only useful when combined with the \fB\-i\fP option). This option is not in the original Korn shell. T} \-f T{ Function mode: display or set functions and their attributes, instead of parameters. T} \-l T{ Lower case attribute: all upper case characters in values are converted to lower case. (In the original Korn shell, this parameter meant `long integer' when used with the \fB\-i\fP option). T} \-p T{ Print complete typeset commands that can be used to re-create the attributes (but not the values) of parameters. This is the default action (option exists for ksh93 compatability). T} \-r T{ Readonly attribute: parameters with the this attribute may not be assigned to or unset. Once this attribute is set, it can not be turned off. T} \-t T{ Tag attribute: has no meaning to the shell; provided for application use. .sp For functions, \fB\-t\fP is the trace attribute. When functions with the trace attribute are executed, the \fBxtrace\fP (\fB\-x\fP) shell option is temporarily turned on. T} \-u T{ Upper case attribute: all lower case characters in values are converted to upper case. (In the original Korn shell, this parameter meant `unsigned integer' when used with the \fB\-i\fP option, which meant upper case letters would never be used for bases greater than 10. See the \fB\-U\fP option). .sp For functions, \fB\-u\fP is the undefined attribute. See Functions above for the implications of this. T} \-x T{ Export attribute: parameters (or functions) are placed in the environment of any executed commands. Exported functions are not implemented yet. T} .TE .\"}}} .\"{{{ ulimit [-acdfHlmnpsStvw] [value] .IP "\fBulimit\fP [\fB\-acdfHlmnpsStvw\fP] [\fIvalue\fP]" Display or set process limits. If no options are used, the file size limit (\fB\-f\fP) is assumed. \fBvalue\fP, if specified, may be either be an arithmetic expression or the word \fBunlimited\fP. The limits affect the shell and any processes created by the shell after a limit is imposed. Note that some systems may not allow limits to be increased once they are set. Also note that the types of limits available are system dependent \- some systems have only the \fB\-f\fP limit. .RS .IP \fB\-a\fP Displays all limits; unless \fB\-H\fP is used, soft limits are displayed. .IP \fB\-H\fP Set the hard limit only (default is to set both hard and soft limits). .IP \fB\-S\fP Set the soft limit only (default is to set both hard and soft limits). .IP \fB\-c\fP Impose a size limit of \fIn\fP blocks on the size of core dumps. .IP \fB\-d\fP Impose a size limit of \fIn\fP kbytes on the size of the data area. .IP \fB\-f\fP Impose a size limit of \fIn\fP blocks on files written by the shell and its child processes (files of any size may be read). .IP \fB\-l\fP Impose a limit of \fIn\fP kbytes on the amount of locked (wired) physical memory. .IP \fB\-m\fP Impose a limit of \fIn\fP kbytes on the amount of physical memory used. .IP \fB\-n\fP Impose a limit of \fIn\fP file descriptors that can be open at once. .IP \fB\-p\fP Impose a limit of \fIn\fP processes that can be run by the user at any one time. .IP \fB\-s\fP Impose a size limit of \fIn\fP kbytes on the size of the stack area. .IP \fB\-t\fP Impose a time limit of \fIn\fP cpu seconds to be used by each process. .IP \fB\-v\fP Impose a limit of \fIn\fP kbytes on the amount of virtual memory used; on some systems this is the maximum allowable virtual address (in bytes, not kbytes). .IP \fB\-w\fP Impose a limit of \fIn\fP kbytes on the amount of swap space used. .PP As far as \fBulimit\fP is concerned, a block is 512 bytes. .RE .\"}}} .\"{{{ umask [-S] [mask] .IP "\fBumask\fP [\fB\-S\fP] [\fImask\fP]" .RS Display or set the file permission creation mask, or umask (see \fIumask\fP(2)). If the \fB\-S\fP option is used, the mask displayed or set is symbolic, otherwise it is an octal number. .sp Symbolic masks are like those used by \fIchmod\fP(1): .RS [\fBugoa\fP]{{\fB=+-\fP}{\fBrwx\fP}*}+[\fB,\fP...] .RE in which the first group of characters is the \fIwho\fP part, the second group is the \fIop\fP part, and the last group is the \fIperm\fP part. The \fIwho\fP part specifies which part of the umask is to be modified. The letters mean: .RS .IP \fBu\fP the user permissions .IP \fBg\fP the group permissions .IP \fBo\fP the other permissions (non-user, non-group) .IP \fBa\fP all permissions (user, group and other) .RE .sp The \fIop\fP part indicates how the \fIwho\fP permissions are to be modified: .RS .IP \fB=\fP set .IP \fB+\fP added to .IP \fB\-\fP removed from .RE .sp The \fIperm\fP part specifies which permissions are to be set, added or removed: .RS .IP \fBr\fP read permission .IP \fBw\fP write permission .IP \fBx\fP execute permission .RE .sp When symbolic masks are used, they describe what permissions may be made available (as opposed to octal masks in which a set bit means the corresponding bit is to be cleared). Example: `ug=rwx,o=' sets the mask so files will not be readable, writable or executable by `others', and is equivalent (on most systems) to the octal mask `07'. .RE .\"}}} .\"{{{ unalias [-adt] name ... .IP "\fBunalias\fP [\fB\-adt\fP] [\fIname1\fP ...]" The aliases for the given names are removed. If the \fB\-a\fP option is used, all aliases are removed. If the \fB\-t\fP or \fB\-d\fP options are used, the indicated operations are carried out on tracked or directory aliases, respectively. .\"}}} .\"{{{ unset [-fv] parameter ... .IP "\fBunset\fP [\fB\-fv\fP] \fIparameter\fP ..." Unset the named parameters (\fB\-v\fP, the default) or functions (\fB\-f\fP). The exit status is non-zero if any of the parameters were already unset, zero otherwise. .\"}}} .\"{{{ wait [job] .IP "\fBwait\fP [\fIjob\fP]" Wait for the specified job(s) to finish. The exit status of wait is that of the last specified job: if the last job is killed by a signal, the exit status is 128 + the number of the signal (see \fBkill \-l\fP \fIexit-status\fP above); if the last specified job can't be found (because it never existed, or had already finished), the exit status of wait is 127. See Job Control below for the format of \fIjob\fP. \fBWait\fP will return if a signal for which a trap has been set is received, or if a HUP, INT or QUIT signal is received. .sp If no jobs are specified, \fBwait\fP waits for all currently running jobs (if any) to finish and exits with a zero status. If job monitoring is enabled, the completion status of jobs is printed (this is not the case when jobs are explicitly specified). .\"}}} .\"{{{ whence [-pv] [name ...] .IP "\fBwhence\fP [\fB\-pv\fP] [name ...]" For each name, the type of command is listed (reserved word, built-in, alias, function, tracked alias or executable). If the \fB\-p\fP option is used, a path search done even if \fIname\fP is a reserved word, alias, \fIetc.\fP Without the \fB\-v\fP option, \fBwhence\fP is similar to \fBcommand \-v\fP except that \fBwhence\fP will find reserved words and won't print aliases as alias commands; with the \fB\-v\fP option, \fBwhence\fP is the same as \fBcommand \-V\fP. Note that for \fBwhence\fP, the \fB\-p\fP option does not affect the search path used, as it does for \fBcommand\fP. If the type of one or more of the names could not be determined, the exit status is non-zero. .\"}}} .\"}}} .\"{{{ job control (and its built-in commands) .SS "Job Control" Job control refers to the shell's ability to monitor and control \fBjobs\fP, which are processes or groups of processes created for commands or pipelines. At a minimum, the shell keeps track of the status of the background (\fIi.e.\fP, asynchronous) jobs that currently exist; this information can be displayed using the \fBjobs\fP command. If job control is fully enabled (using \fBset \-m\fP or \fBset \-o monitor\fP), as it is for interactive shells, the processes of a job are placed in their own process group, foreground jobs can be stopped by typing the suspend character from the terminal (normally ^Z), jobs can be restarted in either the foreground or background, using the \fBfg\fP and \fBbg\fP commands, respectively, and the state of the terminal is saved or restored when a foreground job is stopped or restarted, respectively. .sp Note that only commands that create processes (\fIe.g.\fP, asynchronous commands, subshell commands, and non-built-in, non-function commands) can be stopped; commands like \fBread\fP cannot be. .sp When a job is created, it is assigned a job-number. For interactive shells, this number is printed inside \fB[\fP..\fB]\fP, followed by the process-ids of the processes in the job when an asynchronous command is run. A job may be referred to in \fBbg\fP, \fBfg\fP, \fBjobs\fP, \fBkill\fP and \fBwait\fP commands either by the process id of the last process in the command pipeline (as stored in the \fB$!\fP parameter) or by prefixing the job-number with a percent sign (\fB%\fP). Other percent sequences can also be used to refer to jobs: .sp .TS expand; afB lw(4.5i). %+ T{ The most recently stopped job, or, if there are no stopped jobs, the oldest running job. T} %%\fR, \fP% T{ Same as \fB%+\fP. T} %\- T{ The job that would be the \fB%+\fP job, if the later did not exist. T} %\fIn\fP T{ The job with job-number \fIn\fP. T} %?\fIstring\fP T{ The job containing the string \fIstring\fP (an error occurs if multiple jobs are matched). T} %\fIstring\fP T{ The job starting with string \fIstring\fP (an error occurs if multiple jobs are matched). T} .TE .sp When a job changes state (\fIe.g.\fP, a background job finishes or foreground job is stopped), the shell prints the following status information: .RS \fB[\fP\fInumber\fP\fB]\fP \fIflag status command\fP .RE where .IP "\ \fInumber\fP" is the job-number of the job. .IP "\ \fIflag\fP" is \fB+\fP or \fB-\fP if the job is the \fB%+\fP or \fB%-\fP job, respectively, or space if it is neither. .IP "\ \fIstatus\fP" indicates the current state of the job and can be .RS .IP "\fBRunning\fP" the job has neither stopped or exited (note that running does not necessarily mean consuming CPU time \(em the process could be blocked waiting for some event). .IP "\fBDone\fP [\fB(\fP\fInumber\fP\fB)\fP]" the job exited. \fInumber\fP is the exit status of the job, which is omitted if the status is zero. .IP "\fBStopped\fP [\fB(\fP\fIsignal\fP\fB)\fP]" the job was stopped by the indicated \fIsignal\fP (if no signal is given, the job was stopped by SIGTSTP). .IP "\fIsignal-description\fP [\fB(core dumped)\fP]" the job was killed by a signal (\fIe.g.\fP, Memory\ fault, Hangup, \fIetc.\fP \(em use \fBkill \-l\fP for a list of signal descriptions). The \fB(core\ dumped)\fP message indicates the process created a core file. .RE .IP "\ \fIcommand\fP" is the command that created the process. If there are multiple processes in the job, then each process will have a line showing its \fIcommand\fP and possibly its \fIstatus\fP, if it is different from the status of the previous process. .PP When an attempt is made to exit the shell while there are jobs in the stopped state, the shell warns the user that there are stopped jobs and does not exit. If another attempt is immediately made to exit the shell, the stopped jobs are sent a \fBHUP\fP signal and the shell exits. Similarly, if the \fBnohup\fP option is not set and there are running jobs when an attempt is made to exit a login shell, the shell warns the user and does not exit. If another attempt is immediately made to exit the shell, the running jobs are sent a \fBHUP\fP signal and the shell exits. .\"}}} .\"{{{ Emacs Interactive Input Line Editing .\"}}} .\"{{{ Vi Interactive Input Line Editing .\"}}} .\"}}} .\"{{{ Files .SH FILES ~/.profile .br /etc/profile .br /etc/suid_profile .\"}}} .\"{{{ Notes .SH NOTES Sh is implemented as a runtime option of pdksh, with only those ksh features whose syntax or semantics are incompatible with a traditional Bourne shell disabled. Since this leaves some ksh extensions exposed, caution should be used where backwards compatibility with traditional Bourne or POSIX compliant shells is an issue. .\"}}} .\"{{{ Bugs .SH BUGS Any bugs in pdksh should be reported to pdksh@cs.mun.ca. Please include the version of pdksh (echo $KSH_VERSION shows it), the machine, operating system and compiler you are using and a description of how to repeat the bug (a small shell script that demonstrates the bug is best). The following, if relevant (if you are not sure, include them), can also helpful: options you are using (both options.h options and set \-o options) and a copy of your config.h (the file generated by the configure script). New versions of pdksh can be obtained from ftp.cs.mun.ca:pub/pdksh/. .\"}}} .\"{{{ Authors .SH AUTHORS This shell is based on the public domain 7th edition Bourne shell clone by Charles Forsyth and parts of the BRL shell by Doug A.\& Gwyn, Doug Kingston, Ron Natalie, Arnold Robbins, Lou Salkind and others. The first release of pdksh was created by Eric Gisin, and it was subsequently maintained by John R.\& MacMillan (chance!john@sq.sq.com), and Simon J.\& Gerraty (sjg@zen.void.oz.au). The current maintainer is Michael Rendell (michael@cs.mun.ca). The CONTRIBUTORS file in the source distribution contains a more complete list of people and their part in the shell's development. .\"}}} .\"{{{ See also .SH "SEE ALSO" awk(1), ksh(1), csh(1), ed(1), getconf(1), getopt(1), sed(1), stty(1), vi(1), dup(2), execve(2), getgid(2), getuid(2), open(2), pipe(2), wait(2), getopt(3), rand(3), signal(3), system(3), environ(5) .PP .IR "The KornShell Command and Programming Language" , Morris Bolsky and David Korn, 1989, ISBN 0-13-516972-0. .PP .\" XXX ISBN missing .IR "UNIX Shell Programming" , Stephen G.\& Kochan, Patrick H.\& Wood, Hayden. .PP .IR "IEEE Standard for information Technology \- Portable Operating System Interface (POSIX) \- Part 2: Shell and Utilities" , IEEE Inc, 1993, ISBN 1-55937-255-9. .\"}}}