Linux Commands Examples

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filter nroff output for CRT previewing

see also : col - more - nroff - troff - ul


colcrt [-] [-2] [file ...]

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A typical use of colcrt would be

tbl exum2.n | nroff -ms | colcrt - | more

splitting_command="man $manpage | colcrt - | perl helpfiles"
# Where:
# - `colcrt` is a standard BSD utility that strip out screen control
man 3 $1 2> /dev/null | colcrt \
| grep "#include <.*>" \
| sed -e 's,#include,,' -e 's,<,,' -e 's,>,,' -e 's,[ ]*,,' \
| sort | uniq
exit 0


The colcrt utility provides virtual half-line and reverse line feed sequences for terminals without such capability, and on which overstriking is destructive. Half-line characters and underlining (changed to dashing ’-’) are placed on new lines in between the normal output lines.

The following options are available:


Suppress all underlining. This option is especially useful for previewing allboxed tables from tbl(1).


Cause all half-lines to be printed, effectively double spacing the output. Normally, a minimal space output format is used which will suppress empty lines. The program never suppresses two consecutive empty lines, however. The -2 option is useful for sending output to the line printer when the output contains superscripts and subscripts which would otherwise be invisible.


The LANG, LC_ALL and LC_CTYPE environment variables affect the execution of colcrt as described in environ(7).

exit status

The colcrt utility exits 0 on success, and >0 if an error occurs.


Should fold underlines onto blanks even with the ’-’ option so that a true underline character would show.

Cannot back up more than 102 lines.

General overstriking is lost; as a special case ’|’ overstruck with ’-’ or underline becomes ’+’.

Lines are trimmed to 132 characters.

Some provision should be made for processing superscripts and subscripts in documents which are already double-spaced.

Characters that take up more than one column position may not be underlined correctly.

BSD July 31, 2004 BSD


The colcrt command appeared in 3.0BSD.

see also

col , more , nroff , troff , ul

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