Documentation/col.txt

   1 #       @(#)README      5.1 (Berkeley) 5/22/90
   2
   3 col - filter out reverse line feeds.
   4
   5 In the 32V source code to col(1) the default behavior was to NOT compress
   6 spaces into tabs.  There was a -h option which caused it to compress spaces
   7 into tabs.  There was no -x flag.
   8
   9 The 32V documentation, however, was consistent with the SVID (actually, V7
  10 at the time) and documented a -x flag (as defined above) while making no
  11 mention of a -h flag.  Just before 4.3BSD went out, CSRG updated the manual
  12 page to reflect the way the code worked.  Suspecting that this was probably
  13 the wrong way to go, this version adopts the SVID defaults, and no longer
  14 documents the -h option.
  15
  16 The S5 -p flag is not supported because it isn't clear what it does (looks
  17 like a kludge introduced for a particular printer).
  18
  19 Known differences between AT&T's col and this one (# is delimiter):
  20         Input                   AT&T col                this col
  21         #\nabc\E7def\n#         #   def\nabc\r#         #   def\nabc\n#
  22         #a#                     ##                      #a\n#
  23                 - last line always ends with at least one \n (or \E9)
  24         #1234567 8\n#           #1234567\t8\n#          #1234567 8\n#
  25                 - single space not expanded to tab
  26      -f #a\E8b\n#               #ab\n#                  # b\E9\ra\n#
  27                 - can back up past first line (as far as you want) so you
  28                   *can* have a super script on the first line
  29         #\E9_\ba\E8\nb\n#       #\n_\bb\ba\n#           #\n_\ba\bb\n#
  30                 - always print last character written to a position,
  31                   AT&T col claims to do this but doesn't.
  32
  33 If a character is to be placed on a line that has been flushed, a warning
  34 is produced (the AT&T col is silent).   The -l flag (not in AT&T col) can
  35 be used to increase the number of lines buffered to avoid the problem.
  36
  37 General algorithm: a limited number of lines are buffered in a linked
  38 list.  When a printable character is read, it is put in the buffer of
  39 the current line along with the column it's supposed to be in.  When
  40 a line is flushed, the characters in the line are sorted according to
  41 column and then printed.