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/usr.bin/truncate/truncate.1

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  1.\"
  2.\" Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org>.
  3.\" All rights reserved.
  4.\"
  5.\" Redistribution and use in source and binary forms, with or without
  6.\" modification, are permitted provided that the following conditions
  7.\" are met:
  8.\" 1. Redistributions of source code must retain the above copyright
  9.\"    notice, this list of conditions and the following disclaimer.
 10.\" 2. Redistributions in binary form must reproduce the above copyright
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 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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 17.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 26.\" $FreeBSD$
 27.\"
 28.Dd December 19, 2006
 29.Dt TRUNCATE 1
 30.Os
 31.Sh NAME
 32.Nm truncate
 33.Nd truncate or extend the length of files
 34.Sh SYNOPSIS
 35.Nm
 36.Op Fl c
 37.Bk -words
 38.Fl s Xo
 39.Sm off
 40.Op Cm + | -
 41.Ar size
 42.Op Cm K | k | M | m | G | g | T | t
 43.Sm on
 44.Xc
 45.Ek
 46.Ar
 47.Nm
 48.Op Fl c
 49.Bk -words
 50.Fl r Ar rfile
 51.Ek
 52.Ar
 53.Sh DESCRIPTION
 54The
 55.Nm
 56utility adjusts the length of each regular file given on the command-line.
 57.Pp
 58The following options are available:
 59.Bl -tag -width indent
 60.It Fl c
 61Do not create files if they do not exist.
 62The
 63.Nm
 64utility does not treat this as an error.
 65No error messages are displayed
 66and the exit value is not affected.
 67.It Fl r Ar rfile
 68Truncate or extend files to the length of the file
 69.Ar rfile .
 70.It Fl s Xo
 71.Sm off
 72.Op Cm + | -
 73.Ar size
 74.Op Cm K | k | M | m | G | g | T | t
 75.Sm on
 76.Xc
 77If the
 78.Ar size
 79argument is preceded by a plus sign
 80.Pq Cm + ,
 81files will be extended by this number of bytes.
 82If the
 83.Ar size
 84argument is preceded by a dash
 85.Pq Cm - ,
 86file lengths will be reduced by no more than this number of bytes,
 87to a minimum length of zero bytes.
 88Otherwise, the
 89.Ar size
 90argument specifies an absolute length to which all files
 91should be extended or reduced as appropriate.
 92.Pp
 93The
 94.Ar size
 95argument may be suffixed with one of
 96.Cm K ,
 97.Cm M ,
 98.Cm G
 99or
100.Cm T
101(either upper or lower case) to indicate a multiple of
102Kilobytes, Megabytes, Gigabytes or Terabytes
103respectively.
104.El
105.Pp
106Exactly one of the
107.Fl r
108and
109.Fl s
110options must be specified.
111.Pp
112If a file is made smaller, its extra data is lost.
113If a file is made larger,
114it will be extended as if by writing bytes with the value zero.
115If the file does not exist,
116it is created unless the
117.Fl c
118option is specified.
119.Pp
120Note that,
121while truncating a file causes space on disk to be freed,
122extending a file does not cause space to be allocated.
123To extend a file and actually allocate the space,
124it is necessary to explicitly write data to it,
125using (for example) the shell's
126.Ql >>
127redirection syntax, or
128.Xr dd 1 .
129.Sh EXIT STATUS
130.Ex -std
131If the operation fails for an argument,
132.Nm
133will issue a diagnostic
134and continue processing the remaining arguments.
135.Sh SEE ALSO
136.Xr dd 1 ,
137.Xr touch 1 ,
138.Xr truncate 2
139.Sh STANDARDS
140The
141.Nm
142utility conforms to no known standards.
143.Sh HISTORY
144The
145.Nm
146utility first appeared in
147.Fx 4.2 .
148.Sh AUTHORS
149The
150.Nm
151utility was written by
152.An Sheldon Hearn
153.Aq sheldonh@starjuice.net .