col(1)col(1)NAMEcol - filter reverse line-feeds and backspaces
reads from the standard input and writes onto the standard output. It
performs the line overlays implied by reverse line feeds (ASCII code
and by forward and reverse half-line feeds and is particularly useful
for filtering multi-column output made with the command, and output
resulting from use of the preprocessor (see nroff(1) and tbl(1)).
If the option is given, assumes that the output device in use is not
capable of backspacing. In this case, if two or more characters are to
appear in the same place, only the last one read is output.
If the option is given, assumes the output device is a line printer
(rather than a character printer) and removes backspaces in favor of
multiply overstruck full lines. It generates the minimum number of
print operations necessary to generate the required number of over‐
strikes. (All but the last print operation on a line are separated by
carriage returns (\r); the last print operation is terminated by a new‐
Although accepts half-line motions in its input, it normally does not
emit them on output. Instead, text that would appear between lines is
moved to the next lower full-line boundary. This treatment can be sup‐
pressed by the (fine) option; in this case, the output from may contain
forward half-line feeds (ESC-9), but will still never contain either
kind of reverse line motion.
Unless the option is given, converts white space to tabs on output
wherever possible to shorten printing time.
The ASCII control characters SO (\016) and SI (\017) are assumed by to
start and end text in an alternate character set. The character set to
which each input character belongs is remembered, and on output SI and
SO characters are generated as appropriate to ensure that each charac‐
ter is printed in the correct character set.
On input, the only control characters accepted are space, backspace,
tab, return, new-line, SI, SO, and VT, (\013), and ESC followed by or
The VT character is an alternate form of full reverse line-feed,
included for compatibility with some earlier programs of this type.
All other non-printing characters are ignored.
Normally, ignores any unrecognized escape sequences found in its input;
the option can be used to cause to output these sequences as regular
characters, subject to overprinting from reverse line motions. The use
of this option is highly discouraged unless the user is fully aware of
the textual position of the escape sequences.
The input format accepted by matches the output produced by with either
the or options. Use (and the option of if the ultimate disposition of
the output of is a device that can interpret half-line motions, and
provides a default value for the internationalization variables that
are unset or null. If is unset or null, the default value of "C" (see
lang(5)) is used. If any of the internationalization variables contains
an invalid setting, will behave as if all internationalization vari‐
ables are set to "C". See environ(5).
If set to a non-empty string value, overrides the values of all the
other internationalization variables.
determines the interpretation of text as single and/or multi-byte char‐
acters, the classification of characters as printable, and the charac‐
ters matched by character class expressions in regular expressions.
determines the locale that should be used to affect the format and con‐
tents of diagnostic messages written to standard error and informative
messages written to standard output.
determines the location of message catalogues for the processing of
International Code Set Support
Single- and multi-byte character code sets are supported.
is used most often with and A common usage is:
(very similar to the usual man(1) command). This command allows verti‐
cal bars and outer boxes to be printed for tables. The file is run
through the preprocessor, and the output is then piped through format‐
ting the output using the macros. The formatted output is then piped
through which sets up the vertical bars and aligns the columns in the
file. The file is finally piped through the command, which prints the
output to the screen with underlining and highlighting substituted for
italic and bold typefaces. The option deletes excess space from the
output so that multiple blank lines are not printed to the screen.
This command is likely to be withdrawn from X/Open standards. Applica‐
tions using this command might not be portable to other vendors' sys‐
Cannot back up more than 128 lines. Cannot back up across page bound‐
There is a maximum limit for the number of characters, including
backspaces and overstrikes, on a line. The maximum limit is at least
Local vertical motions that would result in backing up over the first
line of the document are ignored. As a result, the first line must not
have any superscripts.
SEE ALSOnroff(1), tbl(1), ul(1), man(5).