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 hyphenated.

The options are as follows:

Center the text, line by line. In this case, most of the other options are ignored; no splitting or joining of lines is done.
Try to format mail header lines contained in the input sensibly.
Format lines beginning with a ‘.’ (dot) character.
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.
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.)
chars
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.
number
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.
number
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

!}fmt

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).

Center the text in standard input:

$ echo -e 'The merit of all things\nlies\nin their difficulty' | fmt -c
                     The merit of all things
                               lies
                       in their difficulty

Format the text in standard input collapsing spaces:

$ echo -e 'Multiple   spaces    will be collapsed' | fmt -s
Multiple spaces will be collapsed

fold(1), mail(1)

The fmt command appeared in 3BSD.

The version described herein is a complete rewrite and appeared in FreeBSD 4.4.

Kurt Shoens
Liz Allen (added goal length concept)
Gareth McCaughan

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.

October 29, 2020 macOS 15.2