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TRUNCATE(2)		    BSD	System Calls Manual		   TRUNCATE(2)

NAME
     truncate, ftruncate -- truncate or	extend a file to a specified length

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     truncate(const char *path,	off_t length);

     int
     ftruncate(int fd, off_t length);

DESCRIPTION
     The truncate() system call	causes the file	named by path or referenced by
     fd	to be truncated	or extended to length bytes in size.  If the file was
     larger than this size, the	extra data is lost.  If	the file was smaller
     than this size, it	will be	extended as if by writing bytes	with the value
     zero.

     The ftruncate() system call causes	the file or shared memory object back-
     ing the file descriptor fd	to be truncated	or extended to length bytes in
     size.  The	file descriptor	must be	a valid	file descriptor	open for writ-
     ing.  The file position pointer associated	with the file descriptor fd
     will not be modified.

RETURN VALUES
     Upon successful completion, the value 0 is	returned; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.  If	the file to be modified	is not a directory or a	regular	file,
     the truncate() call has no	effect and returns the value 0.

ERRORS
     The truncate() system call	succeeds unless:

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

     [ENAMETOOLONG]	A component of a pathname exceeded 255 characters, or
			an entire path name exceeded 1023 characters.

     [ENOENT]		The named file does not	exist.

     [EACCES]		Search permission is denied for	a component of the
			path prefix.

     [EACCES]		The named file is not writable by the user.

     [ELOOP]		Too many symbolic links	were encountered in translat-
			ing the	pathname.

     [EPERM]		The named file has its immutable or append-only	flag
			set, see the chflags(2)	manual page for	more informa-
			tion.

     [EISDIR]		The named file is 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.

     [EFBIG]		The length argument was	greater	than the maximum file
			size.

     [EINVAL]		The length argument was	less than 0.

     [EIO]		An I/O error occurred updating the inode.

     [EFAULT]		The path argument points outside the process's allo-
			cated address space.

     The ftruncate() system call succeeds unless:

     [EBADF]		The fd argument	is not a valid descriptor.

     [EINVAL]		The fd argument	references a file descriptor that is
			not a regular file or shared memory object.

     [EINVAL]		The fd descriptor is not open for writing.

SEE ALSO
     chflags(2), open(2), shm_open(2)

HISTORY
     The truncate() and	ftruncate() system calls appeared in 4.2BSD.

BUGS
     These calls should	be generalized to allow	ranges of bytes	in a file to
     be	discarded.

     Use of truncate() to extend a file	is not portable.

BSD				  May 4, 2015				   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | BUGS

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