1.\" $NetBSD: col.1,v 1.11 2020/11/01 22:27:15 christos Exp $
  2.\" Copyright (c) 1990, 1993
  3.\"	The Regents of the University of California.  All rights reserved.
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  5.\" This code is derived from software contributed to Berkeley by
  6.\" Michael Rendell.
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 32.\"     @(#)col.1	8.1 (Berkeley) 6/29/93
 33.\" $FreeBSD: head/usr.bin/col/col.1 366913 2020-10-21 16:30:34Z fernape $
 34.\"
 35.Dd November 1, 2020
 36.Dt COL 1
 37.Os
 38.Sh NAME
 39.Nm col
 40.Nd filter reverse line feeds from input
 41.Sh SYNOPSIS
 42.Nm
 43.Op Fl bfhpx
 44.Op Fl l Ar num
 45.Sh DESCRIPTION
 46The
 47.Nm
 48utility filters out reverse (and half reverse) line feeds so that the output is
 49in the correct order with only forward and half forward line
 50feeds, and replaces white-space characters with tabs where possible.
 51.Pp
 52The
 53.Nm
 54utility reads from the standard input and writes to the standard output.
 55.Pp
 56The options are as follows:
 57.Bl -tag -width indent
 58.It Fl b
 59Do not output any backspaces, printing only the last character
 60written to each column position.
 61.It Fl f
 62Forward half line feeds are permitted (``fine'' mode).
 63Normally characters printed on a half line boundary are printed
 64on the following line.
 65.It Fl h
 66Do not output multiple spaces instead of tabs (default).
 67.It Fl l Ar num
 68Buffer at least
 69.Ar num
 70lines in memory.
 71By default, 128 lines are buffered.
 72.It Fl p
 73Force unknown control sequences to be passed through unchanged.
 74Normally,
 75.Nm
 76will filter out any control sequences from the input other than those
 77recognized and interpreted by itself, which are listed below.
 78.It Fl x
 79Output multiple spaces instead of tabs.
 80.El
 81.Pp
 82In the input stream,
 83.Nm
 84understands both the escape sequences of the form escape-digit
 85mandated by
 86.St -susv2
 87and the traditional
 88.Bx
 89format escape-control-character.
 90The control sequences for carriage motion and their ASCII values
 91are as follows:
 92.Pp
 93.Bl -tag -width "carriage return" -compact
 94.It ESC\-BELL
 95reverse line feed (escape then bell).
 96.It ESC\-7
 97reverse line feed (escape then 7).
 98.It ESC\-BACKSPACE
 99half reverse line feed (escape then backspace).
100.It ESC\-8
101half reverse line feed (escape then 8).
102.It ESC\-TAB
103half forward line feed (escape than tab).
104.It ESC\-9
105half forward line feed (escape then 9).
106In
107.Fl f
108mode, this sequence may also occur in the output stream.
109.It backspace
110moves back one column (8); ignored in the first column
111.It carriage return
112(13)
113.It newline
114forward line feed (10); also does carriage return
115.It shift in
116shift to normal character set (15)
117.It shift out
118shift to alternate character set (14)
119.It space
120moves forward one column (32)
121.It tab
122moves forward to next tab stop (9)
123.It vertical tab
124reverse line feed (11)
125.El
126.Pp
127All unrecognized control characters and escape sequences are
128discarded.
129.Pp
130The
131.Nm
132utility keeps track of the character set as characters are read and makes
133sure the character set is correct when they are output.
134.Pp
135If the input attempts to back up to the last flushed line,
136.Nm
137will display a warning message.
138.Sh ENVIRONMENT
139The
140.Ev LANG , LC_ALL
141and
142.Ev LC_CTYPE
143environment variables affect the execution of
144.Nm
145as described in
146.Xr environ 7 .
147.Sh EXIT STATUS
148.Ex -std
149.Sh EXAMPLES
150We can use
151.Nm
152to filter the output of
153.Xr man 1
154and remove the backspace characters (
155.Em ^H
156) before searching for some text:
157.Bd -literal -offset indent
158man ls | col -b | grep HISTORY
159.Ed
160.Sh SEE ALSO
161.Xr expand 1
162.Sh STANDARDS
163The
164.Nm
165utility conforms to
166.St -susv2 .
167.Sh HISTORY
168A
169.Nm
170command
171appeared in
172.At v6 .