truncate(5)

                                  truncate(2)
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   truncate, truncate64, ftruncate, ftruncate64 -- set a file to a
   specified length 

Synopsis

   #include <unistd.h>
   
   int truncate (const char  * path, off_t length);
   
   int truncate64 (const char  * path, off64_t length);
   
   int ftruncate (int fildes, off_t length);
   
   int ftruncate64 (int fildes, off64_t length);

Description

   The file whose name is given by path or referenced by the descriptor
   fildes has its size set to length bytes.

   If the file was previously longer than length, bytes past length will
   no longer be accessible. If it was shorter, bytes from the EOF before
   the call to the EOF after the call will be read in as zeros. The
   effective user ID of the process must have write permission for the
   file, and for ftruncate the file must be open for writing.

Return values

   Upon successful completion, a value of 0 is returned. Otherwise, a
   value of -1 is returned and errno is set to indicate the error.

   truncate and truncate64 fail if one or more of the following are true:

   EACCES
          Search permission is denied on a component of the path prefix.
   EACCES
          Write permission is denied for the file referred to by path.
   EFAULT
          path points outside the process's allocated address space.
   EFBIG
          An attempt is made to write a file that exceeds the process's
          file size limit or the maximum file size (see getrlimit(2) and
          ulimit(2)).
   EINTR
          A signal was caught during execution of the truncate or
          truncate64 routines.
   EINVAL
          path is not an ordinary file.
   EIO
          An I/O error occurred while reading from or writing to the file
          system.
   EISDIR
          The file referred to by path is a directory.
   ELOOP
          Too many symbolic links were encountered in translating path.
   EMFILE
          The maximum number of file descriptors available to the process
          has been reached.
   EMULTIHOP
          Components of path require hopping to multiple remote machines
          and file system type does not allow it.
   ENAMETOOLONG
          The length of a path component exceeds {NAME_MAX} characters,
          or the length of path exceeds {PATH_MAX} characters.
   ENFILE
          Could not allocate any more space for the system file table.
   ENOENT
          Either a component of the path prefix or the file referred to
          by path does not exist.
   ENOLINK
          path points to a remote machine and the link to that machine is
          no longer active.
   ENOTDIR
          A component of the path prefix of path is not a directory.
   EROFS
          The file referred to by path resides on a read-only file
          system.
   ETXTBSY
          The file referred to by path is a pure procedure (shared text)
          file that is being executed.

   ftruncate fails if the following is true:
   EFBIG
          The file is a regular file and length is greater than the
          offset maximum established in the open file descriptor
          associated with fildes.

   ftruncate and ftruncate64 fail if one or more of the following are
   true:
   EAGAIN
          The file exists, mandatory file/record locking is set, and
          there are outstanding record locks on the file (see chmod(2)).
   EBADF
          fildes is not a file descriptor open for writing.
   EINTR
          A signal was caught during execution of the ftruncate or
          ftruncate64 routines.
   EIO
          An I/O error occurred while reading from or writing to the file
          system.
   ENOLINK
          fildes points to a remote machine and the link to that machine
          is no longer active.
   EINVAL
          fildes does not correspond to an ordinary file.

   In general, the system supports blocking truncates, as described in
   fcntl(2), which may result in EDEADLK being set.

References

   fcntl(2), intro(2), open(2)

Notices

  Considerations for large file support

   truncate64 and ftruncate64 support large files, but are otherwise
   identical to truncate and ftruncate, respectively. For details on
   programming for large file capable applications, see ``Large File
   Support'' on intro(2).
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   © 2004 The SCO Group, Inc. All rights reserved.
   UnixWare 7 Release 7.1.4 - 25 April 2004