xref: /freebsd/usr.bin/col/col.1 (revision bdcbfde31e8e9b343f113a1956384bdf30d1ed62)

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.Dd October 21, 2020
.Dt COL 1
.Os
.Sh NAME
.Nm col
.Nd filter reverse line feeds from input
.Sh SYNOPSIS
.Nm
.Op Fl bfhpx
.Op Fl l Ar num
.Sh DESCRIPTION
The
.Nm
utility 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 white-space characters with tabs where possible.
.Pp
The
.Nm
utility reads from the standard input and writes to the standard output.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl b
Do not output any backspaces, printing only the last character
written to each column position.
.It Fl f
Forward half line feeds are permitted (``fine'' mode).
Normally characters printed on a half line boundary are printed
on the following line.
.It Fl h
Do not output multiple spaces instead of tabs (default).
.It Fl l Ar num
Buffer at least
.Ar num
lines in memory.
By default, 128 lines are buffered.
.It Fl p
Force unknown control sequences to be passed through unchanged.
Normally,
.Nm
will filter out any control sequences from the input other than those
recognized and interpreted by itself, which are listed below.
.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 "carriage return" -compact
.It ESC\-BELL
reverse line feed (escape then bell).
.It ESC\-7
reverse line feed (escape then 7).
.It ESC\-BACKSPACE
half reverse line feed (escape then backspace).
.It ESC\-8
half reverse line feed (escape then 8).
.It ESC\-TAB
half forward line feed (escape than tab).
.It ESC\-9
half forward line feed (escape then 9).
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
The
.Nm
utility 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 ENVIRONMENT
The
.Ev LANG , LC_ALL
and
.Ev LC_CTYPE
environment variables affect the execution of
.Nm
as described in
.Xr environ 7 .
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
We can use
.Nm
to filter the output of
.Xr man 1
and remove the backspace characters (
.Em ^H
) before searching for some text:
.Bd -literal -offset indent
man ls | col -b | grep HISTORY
.Ed
.Sh SEE ALSO
.Xr expand 1
.Sh STANDARDS
The
.Nm
utility conforms to
.St -susv2 .
.Sh HISTORY
A
.Nm
command
appeared in
.At v6 .