2004-11-03 13:51:07 +00:00
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.\" Copyright (c) 1983, 1991 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)truncate.2 6.9 (Berkeley) 3/10/91
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.\"
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.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
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.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified 1998-12-21 by Andries Brouwer <aeb@cwi.nl>
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2007-09-20 06:52:22 +00:00
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.\" Modified 2002-01-07 by Michael Kerrisk <mtk.manpages@gmail.com>
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2004-11-03 13:51:07 +00:00
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.\" Modified 2002-04-06 by Andries Brouwer <aeb@cwi.nl>
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2007-09-20 06:52:22 +00:00
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.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
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2004-11-03 13:51:07 +00:00
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.\"
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2011-09-08 15:02:17 +00:00
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.TH TRUNCATE 2 2011-09-08 "Linux" "Linux Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.SH NAME
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truncate, ftruncate \- truncate a file to a specified length
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.SH SYNOPSIS
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.B #include <unistd.h>
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.br
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.B #include <sys/types.h>
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.sp
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.BI "int truncate(const char *" path ", off_t " length );
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.br
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.BI "int ftruncate(int " fd ", off_t " length );
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2007-07-08 12:11:40 +00:00
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.ad l
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2010-09-19 12:37:37 +00:00
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.PD 0
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2007-07-08 12:11:40 +00:00
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.sp
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2009-02-28 01:18:31 +00:00
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.BR truncate ():
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2010-09-18 19:31:53 +00:00
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.RS 4
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2010-09-19 12:37:37 +00:00
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_BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
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_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
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chdir.2, chmod.2, chown.2, gethostname.2, getsid.2, pread.2, setpgid.2, sigaltstack.2, stat.2, truncate.2, wait.2, dirfd.3, getsubopt.3, mkdtemp.3, mkstemp.3, siginterrupt.3, strdup.3: Simplify feature test macro requirements
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-09-26 15:16:57 +00:00
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.br
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|| /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
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2010-09-18 19:31:53 +00:00
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.RE
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2010-09-19 12:37:37 +00:00
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.sp
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2009-02-28 01:18:31 +00:00
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.BR ftruncate ():
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2010-09-18 19:31:53 +00:00
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.RS 4
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2010-09-19 12:37:37 +00:00
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_BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
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_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
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2010-09-27 01:42:30 +00:00
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.br
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|| /* Since glibc 2.3.5: */ _POSIX_C_SOURCE\ >=\ 200112L
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2010-09-18 19:31:53 +00:00
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.RE
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2010-09-19 12:37:37 +00:00
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.PD
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2007-07-08 12:11:40 +00:00
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.ad b
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2004-11-03 13:51:07 +00:00
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.SH DESCRIPTION
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The
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2005-07-19 07:15:17 +00:00
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.BR truncate ()
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2004-11-03 13:51:07 +00:00
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and
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2005-07-19 07:15:17 +00:00
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.BR ftruncate ()
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2004-11-03 13:51:07 +00:00
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functions cause the regular file named by
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.I path
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or referenced by
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.I fd
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to be truncated to a size of precisely
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.I length
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bytes.
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.LP
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2007-04-12 22:42:49 +00:00
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If the file previously was larger than this size, the extra data is lost.
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2004-11-03 13:51:07 +00:00
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If the file previously was shorter, it is extended, and
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2008-06-09 15:49:35 +00:00
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the extended part reads as null bytes (\(aq\\0\(aq).
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2004-11-03 13:51:07 +00:00
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.LP
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2005-07-18 17:10:25 +00:00
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The file offset is not changed.
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2004-11-03 13:51:07 +00:00
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.LP
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2007-04-12 22:42:49 +00:00
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If the size changed, then the st_ctime and st_mtime fields
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2005-07-19 07:15:17 +00:00
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(respectively, time of last status change and
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time of last modification; see
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.BR stat (2))
|
2007-04-12 22:42:49 +00:00
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for the file are updated,
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2005-07-19 07:15:17 +00:00
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and the set-user-ID and set-group-ID permission bits may be cleared.
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2004-11-03 13:51:07 +00:00
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.LP
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With
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2005-07-19 07:15:17 +00:00
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.BR ftruncate (),
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2004-11-03 13:51:07 +00:00
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the file must be open for writing; with
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2005-07-19 07:15:17 +00:00
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.BR truncate (),
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2004-11-03 13:51:07 +00:00
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the file must be writable.
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.SH "RETURN VALUE"
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2007-04-12 22:42:49 +00:00
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On success, zero is returned.
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On error, \-1 is returned, and
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2004-11-03 13:51:07 +00:00
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.I errno
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is set appropriately.
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.SH ERRORS
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For
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2005-10-19 06:54:38 +00:00
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.BR truncate ():
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2004-11-03 13:51:07 +00:00
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.TP
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.B EACCES
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Search permission is denied for a component of the path prefix,
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or the named file is not writable by the user.
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(See also
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2007-05-26 12:41:39 +00:00
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.BR path_resolution (7).)
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2004-11-03 13:51:07 +00:00
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.TP
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.B EFAULT
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.I Path
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points outside the process's allocated address space.
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.TP
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.B EFBIG
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The argument
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.I length
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is larger than the maximum file size. (XSI)
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.TP
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.B EINTR
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2011-09-08 15:02:17 +00:00
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While blocked waiting to complete,
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the call was interrupted by a signal handler; see
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.BR fcntl (2)
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and
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.BR signal (7).
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2004-11-03 13:51:07 +00:00
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.TP
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.B EINVAL
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The argument
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.I length
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is negative or larger than the maximum file size.
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.TP
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.B EIO
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An I/O error occurred updating the inode.
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.TP
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.B EISDIR
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The named file is a directory.
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.TP
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.B ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.TP
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.B ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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2006-02-12 22:19:08 +00:00
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or an entire pathname exceeded 1023 characters.
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2004-11-03 13:51:07 +00:00
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.TP
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.B ENOENT
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The named file does not exist.
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.TP
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.B ENOTDIR
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A component of the path prefix is not a directory.
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.TP
|
2006-05-09 05:28:41 +00:00
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.B EPERM
|
2009-02-28 01:21:00 +00:00
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.\" This happens for at least MSDOS and VFAT file systems
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2006-05-09 05:28:41 +00:00
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.\" on kernel 2.6.13
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The underlying file system does not support extending
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a file beyond its current size.
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.TP
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2004-11-03 13:51:07 +00:00
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.B EROFS
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The named file resides on a read-only file system.
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.TP
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.B ETXTBSY
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The file is a pure procedure (shared text) file that is being executed.
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.PP
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For
|
2005-07-19 07:15:17 +00:00
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.BR ftruncate ()
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2004-11-03 13:51:07 +00:00
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the same errors apply, but instead of things that can be wrong with
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.IR path ,
|
2008-07-04 16:21:39 +00:00
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we now have things that can be wrong with the file descriptor,
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2004-11-03 13:51:07 +00:00
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.IR fd :
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.TP
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.B EBADF
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.I fd
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is not a valid descriptor.
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.TP
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.BR EBADF " or " EINVAL
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.I fd
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is not open for writing.
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.TP
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.B EINVAL
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.I fd
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does not reference a regular file.
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.SH "CONFORMING TO"
|
2006-08-03 13:57:17 +00:00
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4.4BSD, SVr4, POSIX.1-2001 (these calls first appeared in 4.2BSD).
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.\" POSIX.1-1996 has
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.\" .BR ftruncate ().
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.\" POSIX.1-2001 also has
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.\" .BR truncate (),
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.\" as an XSI extension.
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.\" .LP
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.\" SVr4 documents additional
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.\" .BR truncate ()
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.\" error conditions EMFILE, EMULTIHP, ENFILE, ENOLINK. SVr4 documents for
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.\" .BR ftruncate ()
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.\" an additional EAGAIN error condition.
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2004-11-03 13:51:07 +00:00
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.SH NOTES
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2010-11-21 05:17:55 +00:00
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The details in DESCRIPTION are for XSI-compliant systems.
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2004-11-03 13:51:07 +00:00
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For non-XSI-compliant systems, the POSIX standard allows
|
2007-06-08 09:56:56 +00:00
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two behaviors for
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2005-07-19 07:15:17 +00:00
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.BR ftruncate ()
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2004-11-03 13:51:07 +00:00
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when
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.I length
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exceeds the file length
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(note that
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2005-07-19 07:15:17 +00:00
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.BR truncate ()
|
2004-11-03 13:51:07 +00:00
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is not specified at all in such an environment):
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either returning an error, or extending the file.
|
intro.1, time.1, accept.2, bind.2, connect.2, execve.2, flock.2, getdents.2, getpriority.2, getuid.2, intro.2, ioctl.2, mincore.2, mknod.2, personality.2, ptrace.2, read.2, recv.2, select_tut.2, send.2, sendfile.2, shmctl.2, sigaction.2, signal.2, stat.2, times.2, truncate.2, umask.2, wait.2, MB_CUR_MAX.3, MB_LEN_MAX.3, argz_add.3, btowc.3, clearenv.3, clock.3, cmsg.3, end.3, endian.3, errno.3, exit.3, fgetwc.3, fgetws.3, fopen.3, fputwc.3, fputws.3, fseek.3, fwide.3, getfsent.3, getgrnam.3, gethostid.3, getipnodebyname.3, getmntent.3, getpwnam.3, getwchar.3, grantpt.3, iconv.3, iconv_close.3, iconv_open.3, insque.3, intro.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, malloc.3, mblen.3, mbrlen.3, mbrtowc.3, mbsinit.3, mbsnrtowcs.3, mbsrtowcs.3, mbstowcs.3, mbtowc.3, mkstemp.3, mktemp.3, nl_langinfo.3, openpty.3, posix_openpt.3, printf.3, ptsname.3, putwchar.3, qecvt.3, rcmd.3, readdir.3, rexec.3, rpc.3, setnetgrent.3, shm_open.3, sigpause.3, stdin.3, stpcpy.3, strftime.3, strptime.3, syslog.3, towctrans.3, towlower.3, towupper.3, ttyslot.3, ungetwc.3, unlocked_stdio.3, wcpcpy.3, wcpncpy.3, wcrtomb.3, wcscasecmp.3, wcscat.3, wcschr.3, wcscmp.3, wcscpy.3, wcscspn.3, wcsdup.3, wcslen.3, wcsncasecmp.3, wcsncat.3, wcsncmp.3, wcsncpy.3, wcsnlen.3, wcsnrtombs.3, wcspbrk.3, wcsrchr.3, wcsrtombs.3, wcsspn.3, wcsstr.3, wcstok.3, wcstombs.3, wcswidth.3, wctob.3, wctomb.3, wctrans.3, wctype.3, wcwidth.3, wmemchr.3, wmemcmp.3, wmemcpy.3, wmemmove.3, wmemset.3, wprintf.3, console_ioctl.4, pts.4, elf.5, filesystems.5, hosts.5, proc.5, ttytype.5, boot.7, capabilities.7, credentials.7, epoll.7, glob.7, koi8-r.7, path_resolution.7, pty.7, signal.7, suffixes.7, time.7, unicode.7, unix.7, uri.7, utf-8.7: global fix: s/Unix/UNIX/
The man pages were rather inconsistent in the use of "Unix"
versus "UNIX". Let's go with the trademark usage.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-10-12 04:45:38 +00:00
|
|
|
Like most UNIX implementations, Linux follows the XSI requirement
|
2007-04-12 22:42:49 +00:00
|
|
|
when dealing with native file systems.
|
accept.2, access.2, acct.2, clock_nanosleep.2, mbind.2, mincore.2, remap_file_pages.2, sched_setscheduler.2, set_mempolicy.2, splice.2, stat.2, syslog.2, timer_create.2, timerfd_create.2, truncate.2, fenv.3, ferror.3, fflush.3, fgetwc.3, fgetws.3, flockfile.3, fputwc.3, fputws.3, fread.3, getopt.3, gets.3, getwchar.3, glob.3, iconv.3, longjmp.3, pow.3, printf.3, puts.3, putwchar.3, regex.3, rpc.3, scanf.3, setjmp.3, termios.3, unlocked_stdio.3, wcswidth.3, hd.4, rtc.4, st.4, core.5, dir_colors.5, elf.5, proc.5, arp.7, ascii.7, boot.7, bootparam.7, charsets.7, futex.7, ip.7, iso_8859-11.7, man-pages.7, man.7, mdoc.samples.7, path_resolution.7, pipe.7, posixoptions.7, unicode.7, unix.7, uri.7, utf-8.7, ld.so.8: s/non-/non/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 17:20:12 +00:00
|
|
|
However, some nonnative file systems do not permit
|
2006-05-09 05:28:41 +00:00
|
|
|
.BR truncate ()
|
2007-04-12 22:42:49 +00:00
|
|
|
and
|
2006-05-09 05:28:41 +00:00
|
|
|
.BR ftruncate ()
|
|
|
|
to be used to extend a file beyond its current length:
|
|
|
|
a notable example on Linux is VFAT.
|
2004-11-03 13:51:07 +00:00
|
|
|
.\" At the very least: OSF/1, Solaris 7, and FreeBSD conform, mtk, Jan 2002
|
2010-11-21 05:25:39 +00:00
|
|
|
|
|
|
|
The original Linux
|
|
|
|
.BR truncate ()
|
|
|
|
and
|
|
|
|
.BR ftruncate ()
|
|
|
|
system calls were not designed to handle large file offsets.
|
|
|
|
Consequently, Linux 2.4 added
|
|
|
|
.BR truncate64 ()
|
|
|
|
and
|
|
|
|
.BR ftruncate64 ()
|
|
|
|
system calls that handle large files.
|
|
|
|
However, these details can be ignored by applications using glibc, whose
|
2010-12-03 05:56:22 +00:00
|
|
|
wrapper functions transparently employ the more recent system calls
|
2010-11-21 05:25:39 +00:00
|
|
|
where they are available.
|
2010-09-27 01:42:30 +00:00
|
|
|
.SH BUGS
|
|
|
|
A header file bug in glibc 2.12 meant that the minimum value of
|
|
|
|
.\" http://sourceware.org/bugzilla/show_bug.cgi?id=12037
|
|
|
|
.BR _POSIX_C_SOURCE
|
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required to expose the declaration of
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.BR ftruncate ()
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was 200809L instead of 200112L.
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This has been fixed in later glibc versions.
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2004-11-03 13:51:07 +00:00
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.SH "SEE ALSO"
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.BR open (2),
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2007-05-26 12:41:39 +00:00
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.BR stat (2),
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.BR path_resolution (7)
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