|
from small one page howto to huge articles all in one place
poll results
Last additions:
May 25th. 2007:
|
You are here: manpages
TRUNCATE
Section: Linux Programmer's Manual (2)
Updated: 2008-07-04
Index
Return to Main Contents
NAME
truncate, ftruncate - truncate a file to a specified length
SYNOPSIS
#include <unistd.h>
#include <sys/types.h>
int truncate(const char *path, off_t length);
int ftruncate(int fd, off_t length);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
getdtablesize():
_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L
DESCRIPTION
The
truncate()
and
ftruncate()
functions cause the regular file named by
path
or referenced by
fd
to be truncated to a size of precisely
length
bytes.
If the file previously was larger than this size, the extra data is lost.
If the file previously was shorter, it is extended, and
the extended part reads as null bytes (aq\0aq).
The file offset is not changed.
If the size changed, then the st_ctime and st_mtime fields
(respectively, time of last status change and
time of last modification; see
stat(2))
for the file are updated,
and the set-user-ID and set-group-ID permission bits may be cleared.
With
ftruncate(),
the file must be open for writing; with
truncate(),
the file must be writable.
RETURN VALUE
On success, zero is returned.
On error, -1 is returned, and
errno
is set appropriately.
ERRORS
For
truncate():
- EACCES
-
Search permission is denied for a component of the path prefix,
or the named file is not writable by the user.
(See also
path_resolution(7).)
- EFAULT
-
Path
points outside the process's allocated address space.
- EFBIG
-
The argument
length
is larger than the maximum file size. (XSI)
- EINTR
-
A signal was caught during execution.
- EINVAL
-
The argument
length
is negative or larger than the maximum file size.
- EIO
-
An I/O error occurred updating the inode.
- EINTR
-
While blocked waiting to complete,
the call was interrupted by a signal handler; see
fcntl(2)
and
signal(7).
- EISDIR
-
The named file is a directory.
- ELOOP
-
Too many symbolic links were encountered in translating the pathname.
- ENAMETOOLONG
-
A component of a pathname exceeded 255 characters,
or an entire pathname exceeded 1023 characters.
- ENOENT
-
The named file does not exist.
- ENOTDIR
-
A component of the path prefix is not a directory.
- EPERM
-
The underlying file system does not support extending
a file beyond its current size.
- EROFS
-
The named file resides on a read-only file system.
- ETXTBSY
-
The file is a pure procedure (shared text) file that is being executed.
For
ftruncate()
the same errors apply, but instead of things that can be wrong with
path,
we now have things that can be wrong with the file descriptor,
fd:
- EBADF
-
fd
is not a valid descriptor.
- EBADF or EINVAL
-
fd
is not open for writing.
- EINVAL
-
fd
does not reference a regular file.
CONFORMING TO
4.4BSD, SVr4, POSIX.1-2001 (these calls first appeared in 4.2BSD).
NOTES
The above description is for XSI-compliant systems.
For non-XSI-compliant systems, the POSIX standard allows
two behaviors for
ftruncate()
when
length
exceeds the file length
(note that
truncate()
is not specified at all in such an environment):
either returning an error, or extending the file.
Like most Unix implementations, Linux follows the XSI requirement
when dealing with native file systems.
However, some non-native file systems do not permit
truncate()
and
ftruncate()
to be used to extend a file beyond its current length:
a notable example on Linux is VFAT.
SEE ALSO
open(2),
stat(2),
path_resolution(7)
COLOPHON
This page is part of release 3.05 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
Please read "Why adblockers are bad".
Ärger mit Freenet.de
|
other Ads
Other free services
.
.
| 
|
|
- Running on 
-
:
: 
