ULIMIT(3)                  POSIX Programmer's Manual                 ULIMIT(3)



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

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.1-2017, <ulimit.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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 .



IEEE/The Open Group                  2017                            ULIMIT(3)
