TRUNCATE(3P)                                        POSIX Programmer's Manual                                       TRUNCATE(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       truncate - truncate a file to a specified length

SYNOPSIS
       #include <unistd.h>

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


DESCRIPTION
       The truncate() function shall cause the regular file named by path to have a size which shall be equal to length bytes.

       If  the  file  previously  was  larger  than length, the extra data is discarded. If the file was previously shorter than
       length, its size is increased, and the extended area appears as if it were zero-filled.

       The application shall ensure that the process has write permission for the file.

       If the request would cause the file size to exceed the soft file size limit for the process, the request shall  fail  and
       the implementation shall generate the SIGXFSZ signal for the process.

       This  function  shall not modify the file offset for any open file descriptions associated with the file. Upon successful
       completion, if the file size is changed, this function shall mark for update the st_ctime  and  st_mtime  fields  of  the
       file, and the S_ISUID and S_ISGID bits of the file mode may be cleared.

RETURN VALUE
       Upon  successful  completion,  truncate()  shall return 0. Otherwise, -1 shall be returned, and errno set to indicate the
       error.

ERRORS
       The truncate() function shall fail if:

       EINTR  A signal was caught during execution.

       EINVAL The length argument was less than 0.

       EFBIG or EINVAL
              The length argument was greater than the maximum file size.

       EIO    An I/O error occurred while reading from or writing to a file system.

       EACCES A component of the path prefix denies search permission, or write permission is denied on the file.

       EISDIR The named file is a directory.

       ELOOP  A loop exists in symbolic links encountered during resolution of the path argument.

       ENAMETOOLONG
              The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

       ENOENT A component of path does not name an existing file or path is an empty string.

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

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


       The truncate() function may fail if:

       ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the path argument.

       ENAMETOOLONG
              Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       open(), the Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                  TRUNCATE(3P)