FMT(1) General Commands Manual FMT(1)
fmt – simple text formatter
fmt [-cmnps] [-d chars] [-l num] [-t num]
[goal [maximum] | -width | -w width] [file ...]
The fmt utility 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 goal length as
possible without exceeding the maximum. The goal length defaults to 65 and
the maximum to 10 more than the goal length. Alternatively, a single width
parameter can be specified either by prepending a hyphen to it or by using
-w. For example, “fmt -w 72”, “fmt -72”, and “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
The options are as follows:
-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.
-m Try to format mail header lines contained in the input sensibly.
-n Format lines beginning with a ‘.’ (dot) character. Normally, fmt
does not fill these lines, for compatibility with nroff(1).
-p Allow indented paragraphs. Without the -p flag, any change in the
amount of whitespace at the start of a line results in a new
paragraph being begun.
-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.)
Treat the chars (and no others) as sentence-ending characters. By
default the sentence-ending characters are full stop (‘.’),
question mark (‘?’) and exclamation mark (‘!’). Remember that some
characters may need to be escaped to protect them from your shell.
Replace multiple spaces with tabs at the start of each output line,
if possible. Each number spaces will be replaced with one tab.
The default is 8. If number is 0, spaces are preserved.
Assume that the input files' tabs assume number spaces per tab
stop. The default is 8.
The fmt utility is meant to format mail messages prior to sending, but may
also be useful for other simple tasks. For instance, within visual mode of
the ex(1) editor (e.g., vi(1)) the command
will reformat a paragraph, evening the lines.
The LANG, LC_ALL and LC_CTYPE environment variables affect the execution of
fmt as described in environ(7).
fold(1), mail(1), nroff(1)
The fmt command appeared in 3BSD.
The version described herein is a complete rewrite and appeared in
Liz Allen (added goal length concept)
The program was designed to be simple and fast - for more complex
operations, the standard text processors are likely to be more appropriate.
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.
The fmt utility is not infallible in guessing what lines are mail headers
and what lines are not.
macOS 12.1 August 2, 2004 macOS 12.1