col - filter reverse line-feeds
col [-b] [-f] [-x] [-p]
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 multicolumn output made with the
.rt command of nroff and output resulting from use of the 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 will be output.
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 will convert white space to tabs on
output wherever possible to shorten printing time.
The ASCII control characters SO (\017) and SI (\016) 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, 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 nonprinting
characters are ignored.
Normally, col will ignore any escape sequences unknown to it that are
found in its input; the -p option may be used to cause col 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
language-specific message file [See LANG on environ(5).]
nroff(1), tbl(1) in the DOCUMENTER'S WORKBENCH Software Technical
Discussion and Reference Manual
The input format accepted by col matches the output produced by nroff
with either the -T37 or -Tlp options. Use -T37 (and the -f option of
col) if the ultimate disposition of the output of col will be a device
that can interpret half-line motions, and -Tlp otherwise.
col cannot back up more than 256 lines or handle more than 4096
characters per line.
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.
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