colcrt(1) — Linux manual page


COLCRT(1)                     User Commands                    COLCRT(1)

NAME         top

       colcrt - filter nroff output for CRT previewing

SYNOPSIS         top

       colcrt [options] [file ...]

DESCRIPTION         top

       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

OPTIONS         top

       -, --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
           Print version and exit.

HISTORY         top

       The colcrt command appeared in 3.0BSD.

BUGS         top

       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         top

       A typical use of colcrt would be:

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

SEE ALSO         top

       col(1), more(1), nroff(1), troff(1), ul(1)

REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       The colcrt command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨⟩. If you have
       a bug report for this manual page, send it to This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2023-12-22. (At that time, the date of the most recent commit
       that was found in the repository was 2023-12-14.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to

util-linux 2.39.594-1e0ad      2023-07-19                      COLCRT(1)

Pages that refer to this page: ul(1)