.\"	$OpenBSD: col.1,v 1.14 2015/09/14 20:06:58 schwarze Exp $
.\"	$NetBSD: col.1,v 1.4 1995/03/26 05:25:52 glass Exp $
.\"
.\" Copyright (c) 1990, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Michael Rendell.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)col.1	8.1 (Berkeley) 6/29/93
.\"
.Dd $Mdocdate: September 14 2015 $
.Dt COL 1
.Os
.Sh NAME
.Nm col
.Nd filter reverse line feeds and backspaces from input
.Sh SYNOPSIS
.Nm col
.Op Fl bfhx
.Op Fl l Ar num
.Sh DESCRIPTION
.Nm
filters out reverse (and half-reverse) line feeds so that the output is
in the correct order with only forward and half-forward line
feeds, and replaces whitespace characters with tabs where possible.
.Pp
.Nm
reads from the standard input and writes to the standard output.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl b
Do not output any backspaces, printing only the last character
written to each column position.
This can be useful in processing the output of
.Xr mandoc 1 .
.It Fl f
Forward half-line feeds are permitted
.Pf ( Dq fine
mode).
Normally characters printed on a half-line boundary are printed
on the following line.
.It Fl h
Compress spaces into tabs.
This is the default behavior.
.It Fl l Ar num
Buffer at least
.Ar num
lines in memory.
By default, 128 lines are buffered.
.It Fl x
Output multiple spaces instead of tabs.
.El
.Pp
In the input stream,
.Nm
understands both the escape sequences of the form escape-digit
mandated by
.St -susv2
and the traditional
.Bx
format escape-control-character.
The control sequences for carriage motion and their ASCII values
are as follows:
.Pp
.Bl -tag -width "escape-backspace" -compact
.It escape\-bell
Reverse line feed (27 then 7).
.It escape\-digit\-7
Reverse line feed (27 then 55).
.It escape\-backspace
Half reverse line feed (27 then 8).
.It escape\-digit\-8
Half reverse line feed (27 then 56).
.It escape\-tab
Half forward line feed (27 then 9).
.It escape\-digit\-9
Half forward line feed (27 then 57).
In
.Fl f
mode, this sequence may also occur in the output stream.
.It backspace
Moves back one column (8); ignored in the first column.
.It carriage return
(13)
.It newline
Forward line feed (10); also does carriage return.
.It shift in
Shift to normal character set (15).
.It shift out
Shift to alternate character set (14).
.It space
Moves forward one column (32).
.It tab
Moves forward to next tab stop (9).
.It vertical tab
Reverse line feed (11).
.El
.Pp
All unrecognized control characters and escape sequences are
discarded.
.Pp
.Nm
keeps track of the character set as characters are read and makes
sure the character set is correct when they are output.
.Pp
If the input attempts to back up to the last flushed line,
.Nm
will display a warning message.
.Sh SEE ALSO
.Xr expand 1
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .