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1.TH COL 1 "18 January 1983"
2.SH NAME
3col \- filter reverse line feeds
4.SH SYNOPSIS
5.B col
6[
7.B \-bfx
8]
9.SH DESCRIPTION
10.I Col
11reads the standard input and writes the standard output.
12It performs the line overlays implied by reverse line
13feeds (ESC-7 in ASCII)
14and by forward and reverse half line feeds (ESC-9 and ESC-8).
15.I Col
16is particularly useful for filtering multicolumn
17output made with the `.rt' command of
18.I nroff
19and output resulting from use of the
20.IR tbl (1)
21preprocessor.
22.PP
23Although
24.I col
25accepts half line motions in its input, it normally does not
26emit them on output.
27Instead, text that would appear between lines is moved to the next lower
28full line boundary.
29This treatment can be suppressed by the
30.B \-f
31(fine) option; in this case
32the output from
33.I col
34may contain forward half line feeds (ESC-9), but will still never contain
35either kind of reverse line motion.
36.PP
37If the
38.B \-b
39option is given,
40.I col
41assumes that the output device in use is not capable of backspacing.
42In this case, if several characters are to appear in the same place,
43only the last one read will be taken.
44.PP
45The control characters SO (ASCII code 017),
46and SI (016) are assumed
47to start and end text in an alternate character set.
48The character set (primary or alternate) associated with each printing
49character read is remembered; on output, SO and SI characters are generated
50where necessary to maintain the correct treatment of each character.
51.PP
52.I Col
53normally converts white space to tabs to shorten printing time.
54If the
55.B \-x
56option is given, this conversion is suppressed.
57.PP
58All control characters are removed from the input except space,
59backspace,
60tab, return, newline, ESC (033) followed by one of 7, 8, 9, SI, SO, and VT
61(013).
62This last character is an alternate form of full reverse line feed, for
63compatibility with some other hardware conventions.
64All other non-printing characters are ignored.
65.SH "SEE ALSO"
66troff(1), tbl(1)
67.SH BUGS
68Can't back up more than 128 lines.
69.br
70No more than 800 characters, including backspaces, on a line.