.\"	$OpenBSD: expand.1,v 1.9 2003/10/27 12:24:11 jmc Exp $
.\"	$NetBSD: expand.1,v 1.3 1995/09/02 06:19:45 jtc Exp $
.\"
.\" Copyright (c) 1980, 1990, 1993
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.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
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.\"    may be used to endorse or promote products derived from this software
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.\"	@(#)expand.1	8.1 (Berkeley) 6/9/93
.\"
.Dd June 9, 1993
.Dt EXPAND 1
.Os
.Sh NAME
.Nm expand ,
.Nm unexpand
.Nd expand tabs to spaces, and vice versa
.Sh SYNOPSIS
.Nm expand
.Op Fl Ns Ar tabstop
.Oo Xo
.Sm off
.Fl Ar tab1 , tab2 ,
.Ar ... , Ar tabn
.Sm on
.Oc
.Xc
.Op Ar file Ar ...
.Nm expand
.Op Fl t Ar tabstop
.Oo Xo
.Sm off
.Fl t\ \& Ar tab1 , tab2 ,
.Ar ... , Ar tabn
.Sm on
.Oc
.Xc
.Op Ar file Ar ...
.Nm unexpand
.Op Fl a
.Op Ar file Ar ...
.Sh DESCRIPTION
.Nm expand
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.
.Nm expand
is useful for pre-processing character files
(before sorting, looking at specific columns, etc.) that
contain tabs.
.Pp
If a single
.Ar tabstop
argument is given, tabs are set
.Ar tabstop
spaces apart instead of the default 8.
If multiple tabstops are given, then the tabs are set at those
specific columns.
In the synopsis above, both forms of the
.Nm
command are identical.
.Pp
If a list of tabstops is given, it should consist of a list
of two or more positive decimal integers, in ascending order.
In the event of having to process a
.Aq tab
at a position beyond the last of those specified in a multiple tabstop list,
the
.Aq tab
is replaced by a single
.Aq space
character.
.Pp
.Nm unexpand
puts tabs back into the data from the standard input or the named
files and writes the result on the standard output.
.Pp
The options (for
.Nm unexpand
only) are as follows:
.Bl -tag -width flag
.It Fl a
By default, only leading blanks and tabs
are reconverted to maximal strings of tabs.
If the
.Fl a
option is given, tabs are inserted whenever they would compress the
resultant file by replacing two or more characters.
.El
.Sh SEE ALSO
.Xr fold 1
.Sh STANDARDS
The
.Nm
and
.Nm unexpand
utilities are compliant with the
.St -p1003.1
specification, with the following exceptions:
.Bl -bullet -offset indent
.It
.Tn POSIX
does not support specifying tabstops without use of the
.Fl t
flag (first form in
.Sx SYNOPSIS
above).
.It
.Tn POSIX
specifies that multiple tabstops may be given separated by
commas or blanks.
This implementation supports only comma-separated tabstops.
.It
.Nm unexpand
does not recognise the
.Fl t
flag.
.El
.Sh HISTORY
The
.Nm expand
command appeared in
.Bx 3.0 .