2 .\" Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org>.
3 .\" All rights reserved.
5 .\" Redistribution and use in source and binary forms, with or without
6 .\" modification, are permitted provided that the following conditions
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
11 .\" notice, this list of conditions and the following disclaimer in the
12 .\" documentation and/or other materials provided with the distribution.
14 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 .Nd truncate or extend the length of files
42 .Op Cm K | k | M | m | G | g | T | t
56 utility adjusts the length of each regular file given on the command-line.
58 The following options are available:
59 .Bl -tag -width indent
61 Do not create files if they do not exist.
64 utility does not treat this as an error.
65 No error messages are displayed
66 and the exit value is not affected.
68 Truncate or extend files to the length of the file
74 .Op Cm K | k | M | m | G | g | T | t
79 argument is preceded by a plus sign
81 files will be extended by this number of bytes.
84 argument is preceded by a dash
86 file lengths will be reduced by no more than this number of bytes,
87 to a minimum length of zero bytes.
90 argument is preceded by a percent sign
92 files will be round up to a multiple of this number of bytes.
95 argument is preceded by a slash sign
97 files will be round down to a multiple of this number of bytes,
98 to a minimum length of zero bytes.
101 argument specifies an absolute length to which all files
102 should be extended or reduced as appropriate.
106 argument may be suffixed with one of
112 (either upper or lower case) to indicate a multiple of
113 Kilobytes, Megabytes, Gigabytes or Terabytes
121 options must be specified.
123 If a file is made smaller, its extra data is lost.
124 If a file is made larger,
125 it will be extended as if by writing bytes with the value zero.
126 If the file does not exist,
127 it is created unless the
132 while truncating a file causes space on disk to be freed,
133 extending a file does not cause space to be allocated.
134 To extend a file and actually allocate the space,
135 it is necessary to explicitly write data to it,
136 using (for example) the shell's
138 redirection syntax, or
142 If the operation fails for an argument,
144 will issue a diagnostic
145 and continue processing the remaining arguments.
147 Adjust the size of the file
149 to 10 Megabytes but do not create it if it does not exist:
150 .Bd -literal -offset indent
151 truncate -c -s +10M test_file
154 Same as above but create the file if it does not exist:
155 .Bd -literal -offset indent
156 truncate -s +10M test_file
158 -rw-r--r-- 1 root wheel 10485760 Jul 22 18:48 test_file
163 to the size of the kernel and create another file
166 .Bd -literal -offset indent
167 truncate -r /boot/kernel/kernel test_file test_file2
168 ls -l /boot/kernel/kernel test_file*
169 -r-xr-xr-x 1 root wheel 31352552 May 15 14:18 /boot/kernel/kernel*
170 -rw-r--r-- 1 root wheel 31352552 Jul 22 19:15 test_file
171 -rw-r--r-- 1 root wheel 31352552 Jul 22 19:15 test_file2
177 .Bd -literal -offset indent
178 # truncate -s -5M test_file
180 -rw-r--r-- 1 root wheel 26109672 Jul 22 19:17 test_file
181 -rw-r--r-- 1 root wheel 31352552 Jul 22 19:15 test_file2
190 utility conforms to no known standards.
194 utility first appeared in
199 utility was written by
200 .An Sheldon Hearn Aq Mt sheldonh@starjuice.net .