README
1# @(#)README 8.1 (Berkeley) 6/6/93
2#
3# $FreeBSD: src/usr.bin/col/README,v 1.1.1.1.14.1 2001/08/04 01:27:00 mikeh Exp $
4# $DragonFly: src/usr.bin/col/README,v 1.2 2003/06/17 04:29:25 dillon Exp $
5
6col - filter out reverse line feeds.
7
8Options are:
9 -b do not print any backspaces (last character written is printed)
10 -f allow half line feeds in output, by default characters between
11 lines are pushed to the line below
12 -p force unknown control sequences to be passed through unchanged
13 -x do not compress spaces into tabs.
14 -l num keep (at least) num lines in memory, 128 are kept by default
15
16In the 32V source code to col(1) the default behavior was to NOT compress
17spaces into tabs. There was a -h option which caused it to compress spaces
18into tabs. There was no -x flag.
19
20The 32V documentation, however, was consistent with the SVID (actually, V7
21at the time) and documented a -x flag (as defined above) while making no
22mention of a -h flag. Just before 4.3BSD went out, CSRG updated the manual
23page to reflect the way the code worked. Suspecting that this was probably
24the wrong way to go, this version adopts the SVID defaults, and no longer
25documents the -h option.
26
27Known differences between AT&T's col and this one (# is delimiter):
28 Input AT&T col this col
29 #\nabc\E7def\n# # def\nabc\r# # def\nabc\n#
30 #a# ## #a\n#
31 - last line always ends with at least one \n (or \E9)
32 #1234567 8\n# #1234567\t8\n# #1234567 8\n#
33 - single space not expanded to tab
34 -f #a\E8b\n# #ab\n# # b\E9\ra\n#
35 - can back up past first line (as far as you want) so you
36 *can* have a super script on the first line
37 #\E9_\ba\E8\nb\n# #\n_\bb\ba\n# #\n_\ba\bb\n#
38 - always print last character written to a position,
39 AT&T col claims to do this but doesn't.
40
41If a character is to be placed on a line that has been flushed, a warning
42is produced (the AT&T col is silent). The -l flag (not in AT&T col) can
43be used to increase the number of lines buffered to avoid the problem.
44
45General algorithm: a limited number of lines are buffered in a linked
46list. When a printable character is read, it is put in the buffer of
47the current line along with the column it's supposed to be in. When
48a line is flushed, the characters in the line are sorted according to
49column and then printed.
50