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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
ulimit — get and set process limits
SYNOPSIS
#include <ulimit.h> long ulimit(int cmd, ...);
DESCRIPTION
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:
UL_GETFSIZE 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 is unspecified.
UL_SETFSIZE 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 if successful.
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.
RETURN VALUE
Upon successful completion, ulimit() shall return the value of the requested limit. Otherwise, −1 shall
be returned and errno set to indicate the error.
ERRORS
The ulimit() function shall fail and the limit shall be unchanged if:
EINVAL The cmd argument is not valid.
EPERM A process not having appropriate privileges attempts to increase its file size limit.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
Since the ulimit() function uses type long rather than rlim_t, this function is not sufficient for file
sizes on many current systems. Applications should use the getrlimit() or setrlimit() functions instead
of the obsolescent ulimit() function.
RATIONALE
None.
FUTURE DIRECTIONS
The ulimit() function may be removed in a future version.
SEE ALSO
exec, getrlimit(), write()
The Base Definitions volume of POSIX.1‐2008, <ulimit.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .