Section: POSIX Programmer's Manual (3P)
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.
--- get and set process limits
long ulimit(int cmd, ...);
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
with RLIMIT_FSIZE). The
values, defined in
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
the result is unspecified.
Set the file size limit for output operations of the process to the
value of the second argument, taken as a
multiplied by 512. If the result would overflow an
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.
function shall not change the setting of
As all return values are permissible in a successful situation, an
application wishing to check for error situations should set
to 0, then call
and, if it returns -1, check to see if
Upon successful completion,
shall return the value of the requested limit. Otherwise, -1
shall be returned and
set to indicate the error.
function shall fail and the limit shall be unchanged if:
argument is not valid.
A process not having appropriate privileges attempts to increase its
file size limit.
The following sections are informative.
function uses type
this function is not sufficient for file sizes on many current systems.
Applications should use the
functions instead of the obsolescent
function may be removed in a future version.
The Base Definitions volume of POSIX.1-2008,
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
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