---
name: "colcrt"
section: "1"
platform: "linux"
package: "util-linux"
version: "2.42.4-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/colcrt"
---

# colcrt(1)

filter nroff output for CRT previewing

## 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)](/tbl/1.md).

- **-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)](/col/1.md), [**more**(1)](/more/1.md), [**nroff**(1)](/nroff/1.md), [**troff**(1)](/troff/1.md), [**ul**(1)](/ul/1.md)

## 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/\>.