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RedHat 9 (Linux i386) - man page for ftruncate (redhat section 2)

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

       truncate, ftruncate - truncate a file to a specified length

       #include <unistd.h>
       #include <sys/types.h>

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

       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 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

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

       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.

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

       ENOENT The named file does not exist.

	      A component of the path prefix is not a directory.

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

	      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.

       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 error condition.

       The above description is for XSI-compliant systems.  For  non-XSI-compliant  systems,  the
       POSIX  standard	allows	two  behaviours 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.  (Most Unices follow the XSI requirement.)


					    1998-12-21				      TRUNCATE(2)
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