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.