Linux col command

Updated: 05/04/2019 by Computer Hope
col command

On Unix-like operating systems, the col command filters reverse linefeeds from input.

This document covers the GNU/Linux version of col.


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 can be useful in processing the output of nroff and tbl.

The col utility reads from the standard input and writes to the standard output.


col [-bfhpx] [-l num]



Do not output any backspaces, printing only the last character written to each column position.


Forward half line feeds are permitted ("fine" mode). Normally characters printed on a half line boundary are printed on the following line.


Do not output multiple spaces instead of tabs (This is the default).

-l num

Buffer at least num lines in memory. By default, 128 lines are buffered.


Force unknown control sequences to be passed through unchanged. Normally, col will filter out any control sequences from the input other than those recognized and interpreted by itself (which are listed below).


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:


reverse line feed (escape then 7)


half reverse line feed (escape then 8)


half forward line feed (escape then 9)


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.

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.

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.