COLCRT(1) User Commands COLCRT(1)

# [NAME](#NAME)

colcrt - filter nroff output for CRT previewing

# [SYNOPSIS](#SYNOPSIS)

**colcrt** \[options] \[*file* ...]

# [DESCRIPTION](#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](#OPTIONS)

**-**, **--no-underlining**

Suppress all underlining. This option is especially useful for previewing *allboxed* tables from [**tbl**(1)](/man/os/util-linux/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](#HISTORY)

The **colcrt** command appeared in 3.0BSD.

# [BUGS](#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](#EXAMPLES)

A typical use of **colcrt** would be:

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

# [SEE ALSO](#SEE_ALSO)

[**col**(1)](/man/os/util-linux/col.1), [**more**(1)](/man/os/util-linux/more.1), [**nroff**(1)](/man/os/util-linux/nroff.1), [**troff**(1)](/man/os/util-linux/troff.1), [**ul**(1)](/man/os/util-linux/ul.1)

# [REPORTING BUGS](#REPORTING_BUGS)

For bug reports, use the *issue tracker* <https://github.com/util-linux/util-linux/issues>.

# [AVAILABILITY](#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/>.

2026-10-30 util-linux 2.42.4

---

Document: colcrt(1) from util-linux 2.42.4-r2 (Chainguard OS)