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TRUNCATE(2)		   Linux Programmer's Manual		   TRUNCATE(2)

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);

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  ex-
       tended part reads as zero bytes.

       The file	pointer	is not changed.

       If  the	size changed, then the ctime and mtime fields for the file are
       updated,	and suid and sgid mode 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.

       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.

       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
	      path name	exceeded 1023 characters.

       ENOENT The named	file does not exist.

       ENOTDIR
	      A	component of the path prefix is	not a directory.

       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 fd:

       EBADF  The fd is	not a valid descriptor.

       EBADF or	EINVAL
	      The fd is	not open for writing.

       EINVAL The fd does not reference	a regular file.

CONFORMING TO
       4.4BSD, SVr4 (these function calls first	appeared in BSD	 4.2).	 POSIX
       1003.1-1996  has	ftruncate.  POSIX 1003.1-2001 also has truncate, as an
       XSI extension.

       SVr4 documents additional truncate error	conditions  EMFILE,  EMULTIHP,
       ENFILE, ENOLINK.	 SVr4 documents	for ftruncate an additional EAGAIN er-
       ror condition.

NOTES
       The above description is	for XSI-compliant systems.   For  non-XSI-com-
       pliant  systems,	the POSIX standard allows two behaviours for ftruncate
       when length exceeds the file length (note that truncate is  not	speci-
       fied  at	all in such an environment): either returning an error,	or ex-
       tending the file.  (Most	Unices follow the XSI requirement.)

SEE ALSO
       open(2)

				  1998-12-21			   TRUNCATE(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO

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