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/usr.bin/col/README

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