Linux col command
On Unix-like operating systems, the col command filters reverse linefeeds from input.
This page covers the GNU/Linux version of col.
Description
The col utility 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 possible. This is useful in processing the output of nroff and tbl.
The col utility reads from the standard input and writes to the standard output.
Syntax
col [-bfhpx] [-l num]
Options
| -b | Do not output any backspaces, printing only the last character written to each column position. |
| -f | Forward half line feeds are permitted ("fine" mode). Normally characters printed on a half line boundary are printed on the following line. |
| -h | Do not output multiple spaces instead of tabs (default). |
| -l num | Buffer at least num lines in memory. By default, 128 lines are buffered. |
| -p | Force unknown control sequences to be passed through unchanged. Normally, col filters out any control sequences from the input other than those recognized and interpreted by itself (which are listed below). |
| -x | Output multiple spaces instead of tabs. |
Recognized control sequences
The control sequences for carriage motion that col understands and their decimal values are listed in the following table:
| Esc-7 | reverse line feed (escape then 7) |
| Esc-8 | half reverse line feed (escape then 8) |
| Esc-9 | half forward line feed (escape then 9) |
| backspace | moves back one column (8); ignored in the first column |
| carriage return | (13) |
| newline | forward line feed (10); also does carriage return |
| shift in | shift to normal character set (15) |
| shift out | shift to alternate character set (14) |
| space | moves forward one column (32) |
| tab | moves forward to next tab stop (9) |
| vertical tab | reverse line feed (11) |
All unrecognized control characters and escape sequences are discarded.
The col utility keeps track of the character set as characters are read and makes sure the character set is correct when they are output.
If the input attempts to back up to the last flushed line, col displays a warning message.
Related commands
nroff — Format documents for terminal display or line-printer.
tbl — Preprocessor which formats tables for nroff or troff.
troff — Typeset or format documents for terminal display or line-printer.