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.
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, Copyright (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.opengroup.org/unix/online.html