path: root/usr.bin/fmt/fmt.1

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.\"     @(#)fmt.1	8.1 (Berkeley) 6/6/93
.\"
.Dd $Mdocdate: October 24 2016 $
.Dt FMT 1
.Os
.Sh NAME
.Nm fmt
.Nd simple text formatter
.Sh SYNOPSIS
.Nm fmt
.Op Fl cmnps
.Op Fl d Ar chars
.Op Fl l Ar number
.Op Fl t Ar number
.Op Ar goal Oo Ar maximum Oc | Fl Ar width | Fl w Ar width
.Op Ar
.Sh DESCRIPTION
.Nm
is a simple text formatter which reads the concatenation of input
files (or standard input if none are given) and produces on standard
output a version of its input with lines as close to the
.Ar goal
length
as possible without exceeding the
.Ar maximum .
The
.Ar goal
length defaults
to 65 and the
.Ar maximum
to 10 more than the
.Ar goal
length.
.Pp
Alternatively, a single
.Ar width
parameter can be specified either by prepending a hyphen to it or by using
.Fl w .
For example,
.Dq fmt -w 72 ,
.Dq fmt -72 ,
and
.Dq fmt 72 72
all produce identical output.
The spacing at the beginning of the input lines is preserved in the output,
as are blank lines and interword spacing.
Lines are joined or split only at white space; that is, words are never
joined or hyphenated.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl c
Center the text, line by line.
In this case, most of the other
options are ignored; no splitting or joining of lines is done.
.It Fl d Ar chars
Treat
.Ar chars
(and no others) as sentence-ending characters.
By default the
sentence-ending characters are full stop
.Pq Ql \&. ,
question mark
.Pq Ql \&? ,
and exclamation mark
.Pq Ql \&! .
Remember that some characters may need to be
escaped to protect them from the shell.
.It Fl l Ar number
Replace multiple spaces with tabs at the start of each output
line, if possible.
.Ar number
spaces will be replaced with one tab.
.It Fl m
Try to format mail header lines contained in the input sensibly.
.It Fl n
Format lines beginning with a
.Ql \&.
(dot) character.
Normally,
.Nm
does not fill these lines,
for compatibility with troff and nroff.
.It Fl p
Allow indented paragraphs.
Without the
.Fl p
flag, any change in the amount of whitespace at the start of a line
results in a new paragraph being begun.
.It Fl s
Collapse whitespace inside lines, so that multiple whitespace
characters are turned into a single space
(or, at the end of a
sentence, a double space).
.It Fl t Ar number
Assume that the input files' tabs assume
.Ar number
spaces per tab stop.
The default is 8.
.El
.Pp
.Nm
is meant to format mail messages prior to sending, but may also be useful
for other simple tasks.
For instance,
within an editor such as
.Xr vi 1 ,
the following command
will reformat a paragraph,
evening the lines:
.Pp
.Dl !}fmt
.Sh ENVIRONMENT
.Bl -tag -width LC_CTYPE
.It Ev LC_CTYPE
The character encoding
.Xr locale 1 .
It decides which byte sequences form characters
and what their display width is.
If unset or set to
.Qq C ,
.Qq POSIX ,
or an unsupported value, each byte except the tab
is treated as a character of display width 1.
.El
.Sh EXIT STATUS
.Ex -std
The latter happens with invalid options, insufficient memory,
or when an input file is not found or not readable.
The >0 exit value is the sum of all errors up to a maximum of 127;
more errors may occur but the counter will only increment to this number.
.Sh SEE ALSO
.Xr indent 1 ,
.Xr mail 1 ,
.Xr vi 1
.Sh HISTORY
The
.Nm
command first appeared in
.Bx 2 .
.Pp
The version described herein is a complete rewrite and appeared in
.Ox 2.4 .
.Sh AUTHORS
.An Kurt Shoens
(July 1978)
.An Liz Allen
(added goal length concept)
.An Gareth McCaughan
(wrote this version)
.Sh BUGS
The program was designed to be simple and fast \(en for more complex
operations, the standard text processors are likely to be more appropriate.
.Pp
When the first line of an indented paragraph is very long (more than
about twice the goal length), the indentation in the output can be
wrong.
.Pp
.Nm
is not infallible in guessing what lines are mail headers and what
lines are not.