COLCRT(1)			 User Commands			     COLCRT(1)

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).

       -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 partially invisible.

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

       -V, --version
	   Display version 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), more(1), nroff(1), troff(1), ul(1)

REPORTING BUGS
       For bug reports, use the issue tracker
       <https://github.com/util-linux/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 2.41.2		  2025-09-22			     COLCRT(1)