.\"	$OpenBSD: colcrt.1,v 1.7 2000/11/10 05:10:22 aaron Exp $
.\"	$NetBSD: colcrt.1,v 1.3 1995/03/26 05:30:59 glass Exp $
.\"
.\" Copyright (c) 1980, 1990, 1993
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.\"     @(#)colcrt.1	8.1 (Berkeley) 6/30/93
.\"
.Dd June 30, 1993
.Dt COLCRT 1
.Os
.Sh NAME
.Nm colcrt
.Nd filter nroff output for CRT previewing
.Sh SYNOPSIS
.Nm colcrt
.Op Fl
.Op Fl \&2
.Op Ar
.Sh DESCRIPTION
.Nm
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
.Sq - )
are placed on new lines in between the normal output lines.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl
Suppress all underlining.
This option is especially useful for previewing
.Em allboxed
tables from
.Xr tbl 1 .
.It Fl 2
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
.Fl 2
option is useful for sending output to the line printer when the output
contains superscripts and subscripts which would otherwise be invisible.
.El
.Sh EXAMPLES
A typical use of
.Nm
would be
.Bd -literal
tbl exum2.n \&| nroff \-ms \&| colcrt \- \&| more
.Ed
.Sh SEE ALSO
.Xr col 1 ,
.Xr more 1 ,
.Xr nroff 1 ,
.Xr troff 1 ,
.Xr ul 1
.Sh HISTORY
The
.Nm
command appeared in
.Bx 3.0 .
.Sh BUGS
Should fold underlines onto blanks even with the
.Ql Fl
option so that
a true underline character would show.
.Pp
Can't back up more than 102 lines.
.Pp
General overstriking is lost;
as a special case
.Ql |
overstruck with
.Ql -
or underline becomes
.Ql + .
.Pp
Lines are trimmed to 132 characters.
.Pp
Some provision should be made for processing superscripts and subscripts
in documents which are already double-spaced.