.\" Copyright (c) 1980, 1990 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)colcrt.1	6.7 (Berkeley) 03/14/91
.\"
.Dd 
.Dt COLCRT 1
.Os BSD 3
.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 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.
.Pp
Available options:
.Bl -tag -width Ds
.It Fl
Suppress all underlining.
It 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 colcrt
would be
.Bd -literal
tbl exum2.n \&| nroff \-ms \&| colcrt \- \&| more
.Ed
.Sh SEE ALSO
.Xr nroff 1 ,
.Xr troff 1 ,
.Xr col 1 ,
.Xr more 1 ,
.Xr ul 1
.Sh BUGS
Should fold underlines onto blanks even with the
.Ql Fl
option so that
a true underline character would show; if we did this, however,
.Nm colcrt
wouldn't get rid of
.Ar cu Ns 'd
underlining
completely.
.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.
.Sh HISTORY
The
.Nm
command appeared in 
.Bx 3.0 .