ftruncate(2) [ultrix man page]

truncate(2)							System Calls Manual						       truncate(2)

Name
       truncate, ftruncate - truncate a file to a specified length

Syntax
       truncate(path, length)
       char *path;
       int length;

       ftruncate(fd, length)
       int fd, length;

Description
       The  system  call  causes the file named by path or referenced by fd to be truncated to, at most, length bytes in size.	If the file previ-
       ously was larger than this size, the extra data is lost.  With the file must be open for writing.

Return Values
       A value of zero (0) is returned if the call succeeds.  If the call fails, a -1 is returned, and the global  variable  errno  specifies  the
       error.

Restrictions
       Partial blocks discarded as the result of truncation are not zero-filled. This can result in holes in files that do not read as zero.

Diagnostics
       The system call succeeds unless:

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

       [ENOENT]       The named file does not exist.

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

       [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.

       [EFAULT]       The path points outside the process's allocated address space.

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

       [ELOOP]	      Too many symbolic links were encountered in translating the pathname.

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

       The system call succeeds unless:

       [EBADF]	      The fd is not a valid descriptor.

       [EINVAL]       The fd references a socket, not a file.

       [ETIMEDOUT]    A  connect  request  or remote file operation failed, because the connected party did not properly respond after a period of
		      time that is dependent on the communications protocol.

See Also
       open(2)

																       truncate(2)

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.  With ftruncate(), the file must be open for writing.

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 translating the pathname.

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

     [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 allocated address space.

     The ftruncate() system call succeeds unless:

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

     [EINVAL]		The fd argument references a socket, not a file.

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

SEE ALSO

     chflags(2), open(2)

HISTORY

     The truncate() system call 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
								 December 13, 2006							       BSD