.\" Copyright (c) 1980, 1990, 1993
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.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
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.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
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.\"	@(#)expand.1	8.1 (Berkeley) 6/9/93
.\" $FreeBSD: src/usr.bin/expand/expand.1,v 1.3.2.7 2003/02/25 00:54:13 trhodes Exp $
.\" $DragonFly: src/usr.bin/expand/expand.1,v 1.2 2003/06/17 04:29:26 dillon Exp $
.\"
.Dd April 21, 2002
.Dt EXPAND 1
.Os
.Sh NAME
.Nm expand ,
.Nm unexpand
.Nd expand tabs to spaces, and vice versa
.Sh SYNOPSIS
.Nm
.Oo
.Fl t
.Sm off
.Ar tab1 , tab2 , ... , tabn
.Sm on
.Oc
.Op Ar
.Nm unexpand
.Op Fl a
.Oo
.Fl t
.Sm off
.Ar tab1 , tab2 , ... , tabn
.Sm on
.Oc
.Op Ar
.Sh DESCRIPTION
The
.Nm
utility processes the named files or the standard input writing
the standard output with tabs changed into blanks.
Backspace characters are preserved into the output and decrement
the column count for tab calculations.
The
.Nm
utility is useful for pre-processing character files
(before sorting, looking at specific columns, etc.) that
contain tabs.
.Pp
The
.Nm unexpand
utility puts tabs back into the data from the standard input or the named
files and writes the result on the standard output.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl a
.Nm ( unexpand
only.)
By default, only leading blanks and tabs
are reconverted to maximal strings of tabs.  If the
.Fl a
option is given, then tabs are inserted whenever they would compress the
resultant file by replacing two or more characters.
.It Fl t Sm Ar tab1 , tab2 , ... , tabn Sm
Set tab stops at column positions
.Ar tab1 , tab2 , ... , tabn .
If only a single number is given, tab stops are set that number of
column positions apart instead of the default number of 8.
.El
.Sh ENVIRONMENT
The
.Ev LANG , LC_ALL
and
.Ev LC_CTYPE
environment variables affect the execution of
.Nm
and
.Nm unexpand
as described in
.Xr environ 7 .
.Sh EXIT STATUS
.Ex -std expand unexpand
.Sh STANDARDS
The
.Nm
and
.Nm unexpand
utilities conform to
.St -p1003.1-2001 .
.Sh HISTORY
The
.Nm
command appeared in
.Bx 3.0 .