/usr.bin/col/README

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  1. #	@(#)README	8.1 (Berkeley) 6/6/93
    2. 

  2. #
    3. 

  3. # $FreeBSD$
    4. 

  4. 

  5. col - filter out reverse line feeds.
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  6. 

  7. Options are:
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  8. 	-b	do not print any backspaces (last character written is printed)
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  9. 	-f	allow half line feeds in output, by default characters between
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  10. 		lines are pushed to the line below
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  11. 	-p	force unknown control sequences to be passed through unchanged
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  12. 	-x	do not compress spaces into tabs.
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  13. 	-l num	keep (at least) num lines in memory, 128 are kept by default
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  14. 

  15. In the 32V source code to col(1) the default behavior was to NOT compress
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  16. spaces into tabs.  There was a -h option which caused it to compress spaces
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  17. into tabs.  There was no -x flag.
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  18. 

  19. The 32V documentation, however, was consistent with the SVID (actually, V7
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  20. at the time) and documented a -x flag (as defined above) while making no
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  21. mention of a -h flag.  Just before 4.3BSD went out, CSRG updated the manual
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  22. page to reflect the way the code worked.  Suspecting that this was probably
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  23. the wrong way to go, this version adopts the SVID defaults, and no longer
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  24. documents the -h option.
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  25. 

  26. Known differences between AT&T's col and this one (# is delimiter):
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  27. 	Input			AT&T col		this col
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  28. 	#\nabc\E7def\n#		#   def\nabc\r#		#   def\nabc\n#
    29. 

  29. 	#a#			##			#a\n#
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  30. 		- last line always ends with at least one \n (or \E9)
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  31. 	#1234567 8\n#		#1234567\t8\n#		#1234567 8\n#
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  32. 		- single space not expanded to tab
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  33.      -f #a\E8b\n#		#ab\n#			# b\E9\ra\n#
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  34. 		- can back up past first line (as far as you want) so you
    35. 

  35. 		  *can* have a super script on the first line
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  36. 	#\E9_\ba\E8\nb\n#	#\n_\bb\ba\n#		#\n_\ba\bb\n#
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  37. 		- always print last character written to a position,
    38. 

  38. 		  AT&T col claims to do this but doesn't.
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    40. 

  40. If a character is to be placed on a line that has been flushed, a warning
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  41. is produced (the AT&T col is silent).   The -l flag (not in AT&T col) can
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  42. be used to increase the number of lines buffered to avoid the problem.
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  43. 

  44. General algorithm: a limited number of lines are buffered in a linked
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  45. list.  When a printable character is read, it is put in the buffer of
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  46. the current line along with the column it's supposed to be in.  When
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  47. a line is flushed, the characters in the line are sorted according to
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  48. column and then printed.
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