49 lines
2.2 KiB
Text
49 lines
2.2 KiB
Text
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# @(#)README 8.1 (Berkeley) 6/6/93
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col - filter out reverse line feeds.
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Options are:
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-b do not print any backspaces (last character written is printed)
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-f allow half line feeds in output, by default characters between
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lines are pushed to the line below
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-x do not compress spaces into tabs.
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-l num keep (at least) num lines in memory, 128 are kept by default
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In the 32V source code to col(1) the default behavior was to NOT compress
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spaces into tabs. There was a -h option which caused it to compress spaces
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into tabs. There was no -x flag.
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The 32V documentation, however, was consistent with the SVID (actually, V7
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at the time) and documented a -x flag (as defined above) while making no
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mention of a -h flag. Just before 4.3BSD went out, CSRG updated the manual
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page to reflect the way the code worked. Suspecting that this was probably
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the wrong way to go, this version adopts the SVID defaults, and no longer
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documents the -h option.
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The S5 -p flag is not supported because it isn't clear what it does (looks
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like a kludge introduced for a particular printer).
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Known differences between AT&T's col and this one (# is delimiter):
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Input AT&T col this col
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#\nabc\E7def\n# # def\nabc\r# # def\nabc\n#
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#a# ## #a\n#
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- last line always ends with at least one \n (or \E9)
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#1234567 8\n# #1234567\t8\n# #1234567 8\n#
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- single space not expanded to tab
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-f #a\E8b\n# #ab\n# # b\E9\ra\n#
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- can back up past first line (as far as you want) so you
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*can* have a super script on the first line
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#\E9_\ba\E8\nb\n# #\n_\bb\ba\n# #\n_\ba\bb\n#
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- always print last character written to a position,
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AT&T col claims to do this but doesn't.
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If a character is to be placed on a line that has been flushed, a warning
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is produced (the AT&T col is silent). The -l flag (not in AT&T col) can
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be used to increase the number of lines buffered to avoid the problem.
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General algorithm: a limited number of lines are buffered in a linked
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list. When a printable character is read, it is put in the buffer of
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the current line along with the column it's supposed to be in. When
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a line is flushed, the characters in the line are sorted according to
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column and then printed.
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