filter reverse line feeds and
backspaces from input
col filters out reverse (and half-reverse)
line feeds so that the output is in the correct order with only forward and
half-forward line feeds, and replaces whitespace characters with tabs where
col reads from the standard input and
writes to the standard output.
The options are as follows:
- Do not output any backspaces, printing only the last character written to each column position. This can be useful in processing the output of mandoc(1).
- Forward half-line feeds are permitted (“fine” mode). Normally characters printed on a half-line boundary are printed on the following line.
- Compress spaces into tabs. This is the default behavior.
- Buffer at least num lines in memory. By default, 128 lines are buffered.
- Output multiple spaces instead of tabs.
In the input stream,
col understands both
the escape sequences of the form escape-digit mandated by
Version 2 of the Single UNIX Specification
(“SUSv2”) and the traditional
BSD format escape-control-character. The control
sequences for carriage motion and their ASCII values are as follows:
- Reverse line feed (27 then 7).
- Reverse line feed (27 then 55).
- Half reverse line feed (27 then 8).
- Half reverse line feed (27 then 56).
- Half forward line feed (27 then 9).
- Half forward line feed (27 then 57). In
-fmode, this sequence may also occur in the output stream.
- Moves back one column (8); ignored in the first column.
- carriage return
- Forward line feed (10); also does carriage return.
- shift in
- Shift to normal character set (15).
- shift out
- Shift to alternate character set (14).
- Moves forward one column (32).
- Moves forward to next tab stop (9).
- vertical tab
- Reverse line feed (11).
All unrecognized control characters and escape sequences are discarded.
col keeps track of the character set as
characters are read and makes sure the character set is correct when they
If the input attempts to back up to the last flushed line,
col will display a warning message.
col command appeared in
Version 6 AT&T UNIX.