1 .\" Copyright (c) 1983, 1991 The Regents of the University of California.
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. All advertising materials mentioning features or use of this software
13 .\" must display the following acknowledgement:
14 .\" This product includes software developed by the University of
15 .\" California, Berkeley and its contributors.
16 .\" 4. Neither the name of the University nor the names of its contributors
17 .\" may be used to endorse or promote products derived from this software
18 .\" without specific prior written permission.
20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .\" @(#)truncate.2 6.9 (Berkeley) 3/10/91
34 .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
35 .\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
36 .\" Modified 1998-12-21 by Andries Brouwer <aeb@cwi.nl>
37 .\" Modified 2002-01-07 by Michael Kerrisk <mtk.manpages@gmail.com>
38 .\" Modified 2002-04-06 by Andries Brouwer <aeb@cwi.nl>
39 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
41 .TH TRUNCATE 2 2011-09-08 "Linux" "Linux Programmer's Manual"
43 truncate, ftruncate \- truncate a file to a specified length
45 .B #include <unistd.h>
47 .B #include <sys/types.h>
49 .BI "int truncate(const char *" path ", off_t " length );
51 .BI "int ftruncate(int " fd ", off_t " length );
54 Feature Test Macro Requirements for glibc (see
55 .BR feature_test_macros (7)):
62 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
63 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
65 || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
70 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
71 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
73 || /* Since glibc 2.3.5: */ _POSIX_C_SOURCE\ >=\ 200112L
82 functions cause the regular file named by
86 to be truncated to a size of precisely
90 If the file previously was larger than this size, the extra data is lost.
91 If the file previously was shorter, it is extended, and
92 the extended part reads as null bytes (\(aq\\0\(aq).
94 The file offset is not changed.
96 If the size changed, then the st_ctime and st_mtime fields
97 (respectively, time of last status change and
98 time of last modification; see
100 for the file are updated,
101 and the set-user-ID and set-group-ID permission bits may be cleared.
105 the file must be open for writing; with
107 the file must be writable.
109 On success, zero is returned.
110 On error, \-1 is returned, and
112 is set appropriately.
118 Search permission is denied for a component of the path prefix,
119 or the named file is not writable by the user.
121 .BR path_resolution (7).)
125 points outside the process's allocated address space.
130 is larger than the maximum file size. (XSI)
133 While blocked waiting to complete,
134 the call was interrupted by a signal handler; see
142 is negative or larger than the maximum file size.
145 An I/O error occurred updating the inode.
148 The named file is a directory.
151 Too many symbolic links were encountered in translating the pathname.
154 A component of a pathname exceeded 255 characters,
155 or an entire pathname exceeded 1023 characters.
158 The named file does not exist.
161 A component of the path prefix is not a directory.
164 .\" This happens for at least MSDOS and VFAT file systems
166 The underlying file system does not support extending
167 a file beyond its current size.
170 The named file resides on a read-only file system.
173 The file is a pure procedure (shared text) file that is being executed.
177 the same errors apply, but instead of things that can be wrong with
179 we now have things that can be wrong with the file descriptor,
184 is not a valid descriptor.
186 .BR EBADF " or " EINVAL
188 is not open for writing.
192 does not reference a regular file.
194 4.4BSD, SVr4, POSIX.1-2001 (these calls first appeared in 4.2BSD).
196 .\" .BR ftruncate ().
197 .\" POSIX.1-2001 also has
199 .\" as an XSI extension.
201 .\" SVr4 documents additional
203 .\" error conditions EMFILE, EMULTIHP, ENFILE, ENOLINK. SVr4 documents for
205 .\" an additional EAGAIN error condition.
207 The details in DESCRIPTION are for XSI-compliant systems.
208 For non-XSI-compliant systems, the POSIX standard allows
213 exceeds the file length
216 is not specified at all in such an environment):
217 either returning an error, or extending the file.
218 Like most UNIX implementations, Linux follows the XSI requirement
219 when dealing with native file systems.
220 However, some nonnative file systems do not permit
224 to be used to extend a file beyond its current length:
225 a notable example on Linux is VFAT.
226 .\" At the very least: OSF/1, Solaris 7, and FreeBSD conform, mtk, Jan 2002
232 system calls were not designed to handle large file offsets.
233 Consequently, Linux 2.4 added
237 system calls that handle large files.
238 However, these details can be ignored by applications using glibc, whose
239 wrapper functions transparently employ the more recent system calls
240 where they are available.
242 A header file bug in glibc 2.12 meant that the minimum value of
243 .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12037
245 required to expose the declaration of
247 was 200809L instead of 200112L.
248 This has been fixed in later glibc versions.
252 .BR path_resolution (7)