The ulimit() function shall control process limits. The process
limits that can be controlled by this function include
the maximum size of a single file that can be written (this is equivalent
to using setrlimit() with RLIMIT_FSIZE). The cmd values,
defined in <ulimit.h>, include:
Return the file size limit (RLIMIT_FSIZE) of the process. The limit
shall be in units of 512-byte blocks and shall be inherited
by child processes. Files of any size can be read. The return value
shall be the integer part of the soft file size limit divided
by 512. If the result cannot be represented as a long, the result
Set the file size limit for output operations of the process to the
value of the second argument, taken as a long,
multiplied by 512. If the result would overflow an rlim_t, the
actual value set is unspecified. Any process may decrease its
own limit, but only a process with appropriate privileges may increase
the limit. The return value shall be the integer part of the
new file size limit divided by 512.
The ulimit() function shall not change the setting of errno
As all return values are permissible in a successful situation, an
application wishing to check for error situations should set
errno to 0, then call ulimit(), and, if it returns -1,
check to see if errno is non-zero.
Upon successful completion, ulimit() shall return the value
of the requested limit. Otherwise, -1 shall be returned and
errno set to indicate the error.
The ulimit() function shall fail and the limit shall be unchanged
The cmd argument is not valid.
A process not having appropriate privileges attempts to increase its
file size limit.
The following sections are informative.
getrlimit() , setrlimit() , write() , the Base Definitions
volume of IEEE Std 1003.1-2001, <ulimit.h>
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