colcrt - Man Page

filter nroff output for CRT previewing


colcrt [options] [file ...]


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.


-, --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.


The colcrt command appeared in 3.0BSD.


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.


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 at


The colcrt command is part of the util-linux package which can be downloaded from Linux Kernel Archive.

Referenced By


2023-06-14 util-linux 2.39.2