NAME [Toc] [Back]
col - filter reverse line-feeds and backspaces
SYNOPSIS [Toc] [Back]
DESCRIPTION [Toc] [Back]
col reads from the standard input and writes onto the standard output.
It performs the line overlays implied by reverse line feeds (ASCII
code ESC-7), and by forward and reverse half-line feeds (ESC-9 and
ESC-8). col is particularly useful for filtering multi-column output
made with the nroff .rt command, and output resulting from use of the
tbl preprocessor (see nroff(1) and tbl(1)).
If the -b option is given, col 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
If the -l option is given, col 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 overstrikes. (All but the last print operation on a line are
separated by carriage returns (\r); the last print operation is
terminated by a newline (\n).)
Although col 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 suppressed by the -f (fine) option; in this case, the output
from col may contain forward half-line feeds (ESC-9), but will still
never contain either kind of reverse line motion.
Unless the -x option is given, col 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
col 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 character 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
7, 8, or 9. 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, col ignores any unrecognized escape sequences found in its
input; the -p option can be used to cause col to output these
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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.
EXTERNAL INFLUENCES [Toc] [Back]
LANG provides a default value for the internationalization variables
that are unset or null. If LANG is unset or null, the default value of
"C" (see lang(5)) is used. If any of the internationalization
variables contains an invalid setting, col will behave as if all
internationalization variables are set to "C". See environ(5).
LC_ALL If set to a non-empty string value, overrides the values of all
the other internationalization variables.
LC_CTYPE determines the interpretation of text as single and/or
multi-byte characters, the classification of characters as printable,
and the characters matched by character class expressions in regular
LC_MESSAGES determines the locale that should be used to affect the
format and contents of diagnostic messages written to standard error
and informative messages written to standard output.
NLSPATH determines the location of message catalogues for the
processing of LC_MESSAGES.
International Code Set Support [Toc] [Back]
Single- and multi-byte character code sets are supported.
EXAMPLES [Toc] [Back]
col is used most often with nroff and tbl. A common usage is:
tbl filename | nroff -man | col | more -s
(very similar to the usual man(1) command). This command allows
vertical bars and outer boxes to be printed for tables. The file is
run through the tbl preprocessor, and the output is then piped through
nroff, formatting the output using the -man macros. The formatted
output is then piped through col, which sets up the vertical bars and
aligns the columns in the file. The file is finally piped through the
more command, which prints the output to the screen with underlining
and highlighting substituted for italic and bold typefaces. The -s
option deletes excess space from the output so that multiple blank
lines are not printed to the screen.
SEE ALSO [Toc] [Back]
nroff(1), tbl(1), ul(1), man(5).
NOTES [Toc] [Back]
The input format accepted by col matches the output produced by nroff
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with either the -T37 or -Tlp options. Use -T37 (and the -f option of
col) if the ultimate disposition of the output of col is a device that
can interpret half-line motions, and -Tlp otherwise.
BUGS [Toc] [Back]
Cannot back up more than 128 lines. Cannot back up across page
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.
WARNINGS [Toc] [Back]
This command is likely to be withdrawn from X/Open standards.
Applications using this command might not be portable to other
STANDARDS CONFORMANCE [Toc] [Back]
col: SVID2, SVID3, XPG2, XPG3
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