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Annotation of src/usr.bin/col/README, Revision 1.2

1.2     ! deraadt     1: #      $OpenBSD$
        !             2:
1.1       deraadt     3: #      @(#)README      8.1 (Berkeley) 6/6/93
                      4:
                      5: col - filter out reverse line feeds.
                      6:
                      7: Options 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:        -x      do not compress spaces into tabs.
                     12:        -l num  keep (at least) num lines in memory, 128 are kept by default
                     13:
                     14: In the 32V source code to col(1) the default behavior was to NOT compress
                     15: spaces into tabs.  There was a -h option which caused it to compress spaces
                     16: into tabs.  There was no -x flag.
                     17:
                     18: The 32V documentation, however, was consistent with the SVID (actually, V7
                     19: at the time) and documented a -x flag (as defined above) while making no
                     20: mention of a -h flag.  Just before 4.3BSD went out, CSRG updated the manual
                     21: page to reflect the way the code worked.  Suspecting that this was probably
                     22: the wrong way to go, this version adopts the SVID defaults, and no longer
                     23: documents the -h option.
                     24:
                     25: The S5 -p flag is not supported because it isn't clear what it does (looks
                     26: like a kludge introduced for a particular printer).
                     27:
                     28: Known differences between AT&T's col and this one (# is delimiter):
                     29:        Input                   AT&T col                this col
                     30:        #\nabc\E7def\n#         #   def\nabc\r#         #   def\nabc\n#
                     31:        #a#                     ##                      #a\n#
                     32:                - last line always ends with at least one \n (or \E9)
                     33:        #1234567 8\n#           #1234567\t8\n#          #1234567 8\n#
                     34:                - single space not expanded to tab
                     35:      -f #a\E8b\n#              #ab\n#                  # b\E9\ra\n#
                     36:                - can back up past first line (as far as you want) so you
                     37:                  *can* have a super script on the first line
                     38:        #\E9_\ba\E8\nb\n#       #\n_\bb\ba\n#           #\n_\ba\bb\n#
                     39:                - always print last character written to a position,
                     40:                  AT&T col claims to do this but doesn't.
                     41:
                     42: If a character is to be placed on a line that has been flushed, a warning
                     43: is produced (the AT&T col is silent).   The -l flag (not in AT&T col) can
                     44: be used to increase the number of lines buffered to avoid the problem.
                     45:
                     46: General algorithm: a limited number of lines are buffered in a linked
                     47: list.  When a printable character is read, it is put in the buffer of
                     48: the current line along with the column it's supposed to be in.  When
                     49: a line is flushed, the characters in the line are sorted according to
                     50: column and then printed.