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COLCRT(1) BSD General Commands Manual COLCRT(1)


colcrt — filter nroff output for CRT previewing


colcrt [] [−2] [file ...]


The colcrt utility 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.

The following options are available:

Suppress all underlining. This option is especially useful for previewing allboxed tables from tbl(1).


Cause 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 invisible.


The LANG, LC_ALL and LC_CTYPE environment variables affect the execution of colcrt as described in environ(7).


The colcrt utility exits 0 on success, and >0 if an error occurs.


A typical use of colcrt would be

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


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


The colcrt command appeared in 3.0BSD.


Should fold underlines onto blanks even with the ’’ option so that a true underline character would show.

Cannot 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.

Characters that take up more than one column position may not be underlined correctly.

BSD July 31, 2004 BSD

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