Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
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);

   Feature Test	Macro Requirements for glibc (see feature_test_macros(7)):

       truncate():
	   _BSD_SOURCE || _XOPEN_SOURCE	>= 500 ||
	   _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
	   || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L

       ftruncate():
	   _BSD_SOURCE || _XOPEN_SOURCE	>= 500 ||
	   _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
	   || /* Since glibc 2.3.5: */ _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  ex-
       tended part reads as null bytes ('\0').

       The file	offset is not changed.

       If  the	size  changed,	then the st_ctime and st_mtime fields (respec-
       tively, 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  While blocked waiting to complete, the call was interrupted by a
	      signal handler; see fcntl(2) and signal(7).

       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
	      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 filesystem	does not support extending a file  be-
	      yond its current size.

       EROFS  The named	file resides on	a read-only filesystem.

       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 details in DESCRIPTION are for XSI-compliant	systems.  For non-XSI-
       compliant  systems,  the	POSIX standard allows two behaviors for	ftrun-
       cate() 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 filesystems.	 However, some
       nonnative filesystems do	not permit truncate() and  ftruncate()	to  be
       used  to	 extend	a file beyond its current length: a notable example on
       Linux is	VFAT.

       The original Linux truncate() and ftruncate() system calls were not de-
       signed  to  handle  large  file offsets.	 Consequently, Linux 2.4 added
       truncate64() and	ftruncate64() system calls that	 handle	 large	files.
       However,	 these	details	 can  be  ignored by applications using	glibc,
       whose wrapper functions transparently employ  the  more	recent	system
       calls where they	are available.

       On  some	 32-bit	 architectures,	the calling signature for these	system
       calls differ, for the reasons described in syscall(2).

BUGS
       A header	file bug in  glibc  2.12  meant	 that  the  minimum  value  of
       _POSIX_C_SOURCE	required  to expose the	declaration of ftruncate() was
       200809L instead of 200112L.  This has been fixed	in  later  glibc  ver-
       sions.

SEE ALSO
       open(2),	stat(2), path_resolution(7)

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2013-04-01			   TRUNCATE(2)

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

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=truncate&sektion=2&manpath=Debian+8.1.0>

home | help