# info > colcrt

[COLCRT(1)](https://www.chedong.com/phpMan.php/man/COLCRT/1/markdown)                        User Commands                       [COLCRT(1)](https://www.chedong.com/phpMan.php/man/COLCRT/1/markdown)

## NAME
       colcrt - filter nroff output for CRT previewing

## SYNOPSIS
       colcrt [options] [file ...]

## DESCRIPTION
       colcrt 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.

## OPTIONS
       -, --no-underlining
           Suppress all underlining. This option is especially useful for
           previewing allboxed tables from [tbl(1)](https://www.chedong.com/phpMan.php/man/tbl/1/markdown).

       -2, --half-lines
           Causes 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.

### -V, --version
           Display version information and exit.

### -h, --help
           Display help text and exit.

## HISTORY
       The colcrt command appeared in 3.0BSD.

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

       Can't 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.

## EXAMPLES
       A typical use of colcrt would be:

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

## SEE ALSO
       [col(1)](https://www.chedong.com/phpMan.php/man/col/1/markdown), [more(1)](https://www.chedong.com/phpMan.php/man/more/1/markdown), [nroff(1)](https://www.chedong.com/phpMan.php/man/nroff/1/markdown), [troff(1)](https://www.chedong.com/phpMan.php/man/troff/1/markdown), [ul(1)](https://www.chedong.com/phpMan.php/man/ul/1/markdown)

## REPORTING BUGS
       For bug reports, use the issue tracker at
       <https://github.com/karelzak/util-linux/issues>.

## AVAILABILITY
       The colcrt command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <<https://www.kernel.org/pub/linux/utils/util-linux/>>.

util-linux 2.37.2                 2021-06-02                         [COLCRT(1)](https://www.chedong.com/phpMan.php/man/COLCRT/1/markdown)