.\"
.\" Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org>.
.\" All rights reserved.
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
.\"
.\" $FreeBSD$
.\"
.Dd December 19, 2006
.Dt TRUNCATE 1
.Os
.Sh NAME
.Nm truncate
.Nd truncate or extend the length of files
.Sh SYNOPSIS
.Nm
.Op Fl c
.Bk -words
.Fl s Xo
.Sm off
.Op Cm + | -
.Ar size
.Op Cm K | k | M | m | G | g | T | t
.Sm on
.Xc
.Ek
.Ar
.Nm
.Op Fl c
.Bk -words
.Fl r Ar rfile
.Ek
.Ar
.Sh DESCRIPTION
The
.Nm
utility adjusts the length of each regular file given on the command-line.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl c
Do not create files if they do not exist.
The
.Nm
utility does not treat this as an error.
No error messages are displayed
and the exit value is not affected.
.It Fl r Ar rfile
Truncate or extend files to the length of the file
.Ar rfile .
.It Fl s Xo
.Sm off
.Op Cm + | -
.Ar size
.Op Cm K | k | M | m | G | g | T | t
.Sm on
.Xc
If the
.Ar size
argument is preceded by a plus sign
.Pq Cm + ,
files will be extended by this number of bytes.
If the
.Ar size
argument is preceded by a dash
.Pq Cm - ,
file lengths will be reduced by no more than this number of bytes,
to a minimum length of zero bytes.
Otherwise, the
.Ar size
argument specifies an absolute length to which all files
should be extended or reduced as appropriate.
.Pp
The
.Ar size
argument may be suffixed with one of
.Cm K ,
.Cm M ,
.Cm G
or
.Cm T
(either upper or lower case) to indicate a multiple of
Kilobytes, Megabytes, Gigabytes or Terabytes
respectively.
.El
.Pp
Exactly one of the
.Fl r
and
.Fl s
options must be specified.
.Pp
If a file is made smaller, its extra data is lost.
If a file is made larger,
it will be extended as if by writing bytes with the value zero.
If the file does not exist,
it is created unless the
.Fl c
option is specified.
.Pp
Note that,
while truncating a file causes space on disk to be freed,
extending a file does not cause space to be allocated.
To extend a file and actually allocate the space,
it is necessary to explicitly write data to it,
using (for example) the shell's
.Ql >>
redirection syntax, or
.Xr dd 1 .
.Sh EXIT STATUS
.Ex -std
If the operation fails for an argument,
.Nm
will issue a diagnostic
and continue processing the remaining arguments.
.Sh SEE ALSO
.Xr dd 1 ,
.Xr touch 1 ,
.Xr truncate 2
.Sh STANDARDS
The
.Nm
utility conforms to no known standards.
.Sh HISTORY
The
.Nm
utility first appeared in
.Fx 4.2 .
.Sh AUTHORS
The
.Nm
utility was written by
.An Sheldon Hearn
.Aq sheldonh@starjuice.net .