NAME

     colcrt — filter nroff output for CRT previewing

SYNOPSIS

     colcrt [-] [-2] [file ...]

DESCRIPTION

     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).

     -2      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.

ENVIRONMENT

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

EXIT STATUS

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

EXAMPLES

     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)

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.

     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.