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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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GETRLIMIT(3P) POSIX Programmer's Manual GETRLIMIT(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.
getrlimit, setrlimit — control maximum resource consumption
#include <sys/resource.h>
int getrlimit(int resource, struct rlimit *rlp);
int setrlimit(int resource, const struct rlimit *rlp);
The getrlimit() function shall get, and the setrlimit() function
shall set, limits on the consumption of a variety of resources.
Each call to either getrlimit() or setrlimit() identifies a
specific resource to be operated upon as well as a resource limit.
A resource limit is represented by an rlimit structure. The
rlim_cur member specifies the current or soft limit and the
rlim_max member specifies the maximum or hard limit. Soft limits
may be changed by a process to any value that is less than or
equal to the hard limit. A process may (irreversibly) lower its
hard limit to any value that is greater than or equal to the soft
limit. Only a process with appropriate privileges can raise a hard
limit. Both hard and soft limits can be changed in a single call
to setrlimit() subject to the constraints described above.
The value RLIM_INFINITY, defined in <sys/resource.h>, shall be
considered to be larger than any other limit value. If a call to
getrlimit() returns RLIM_INFINITY for a resource, it means the
implementation shall not enforce limits on that resource.
Specifying RLIM_INFINITY as any resource limit value on a
successful call to setrlimit() shall inhibit enforcement of that
resource limit.
The following resources are defined:
RLIMIT_CORE This is the maximum size of a core file, in bytes,
that may be created by a process. A limit of 0 shall
prevent the creation of a core file. If this limit
is exceeded, the writing of a core file shall
terminate at this size.
RLIMIT_CPU This is the maximum amount of CPU time, in seconds,
used by a process. If this limit is exceeded,
SIGXCPU shall be generated for the process. If the
process is catching or ignoring SIGXCPU, or all
threads belonging to that process are blocking
SIGXCPU, the behavior is unspecified.
RLIMIT_DATA This is the maximum size of a data segment of the
process, in bytes. If this limit is exceeded, the
malloc() function shall fail with errno set to
[ENOMEM].
RLIMIT_FSIZE This is the maximum size of a file, in bytes, that
may be created by a process. If a write or truncate
operation would cause this limit to be exceeded,
SIGXFSZ shall be generated for the thread. If the
thread is blocking, or the process is catching or
ignoring SIGXFSZ, continued attempts to increase the
size of a file from end-of-file to beyond the limit
shall fail with errno set to [EFBIG].
RLIMIT_NOFILE This is a number one greater than the maximum value
that the system may assign to a newly-created
descriptor. If this limit is exceeded, functions
that allocate a file descriptor shall fail with
errno set to [EMFILE]. This limit constrains the
number of file descriptors that a process may
allocate.
RLIMIT_STACK This is the maximum size of the initial thread's
stack, in bytes. The implementation does not
automatically grow the stack beyond this limit. If
this limit is exceeded, SIGSEGV shall be generated
for the thread. If the thread is blocking SIGSEGV,
or the process is ignoring or catching SIGSEGV and
has not made arrangements to use an alternate stack,
the disposition of SIGSEGV shall be set to SIG_DFL
before it is generated.
RLIMIT_AS This is the maximum size of total available memory
of the process, in bytes. If this limit is exceeded,
the malloc() and mmap() functions shall fail with
errno set to [ENOMEM]. In addition, the automatic
stack growth fails with the effects outlined above.
When using the getrlimit() function, if a resource limit can be
represented correctly in an object of type rlim_t, then its
representation is returned; otherwise, if the value of the
resource limit is equal to that of the corresponding saved hard
limit, the value returned shall be RLIM_SAVED_MAX; otherwise, the
value returned shall be RLIM_SAVED_CUR.
When using the setrlimit() function, if the requested new limit is
RLIM_INFINITY, the new limit shall be ``no limit''; otherwise, if
the requested new limit is RLIM_SAVED_MAX, the new limit shall be
the corresponding saved hard limit; otherwise, if the requested
new limit is RLIM_SAVED_CUR, the new limit shall be the
corresponding saved soft limit; otherwise, the new limit shall be
the requested value. In addition, if the corresponding saved limit
can be represented correctly in an object of type rlim_t then it
shall be overwritten with the new limit.
The result of setting a limit to RLIM_SAVED_MAX or RLIM_SAVED_CUR
is unspecified unless a previous call to getrlimit() returned that
value as the soft or hard limit for the corresponding resource
limit.
The determination of whether a limit can be correctly represented
in an object of type rlim_t is implementation-defined. For
example, some implementations permit a limit whose value is
greater than RLIM_INFINITY and others do not.
The exec family of functions shall cause resource limits to be
saved.
Upon successful completion, getrlimit() and setrlimit() shall
return 0. Otherwise, these functions shall return -1 and set errno
to indicate the error.
The getrlimit() and setrlimit() functions shall fail if:
EINVAL An invalid resource was specified; or in a setrlimit()
call, the new rlim_cur exceeds the new rlim_max.
EPERM The limit specified to setrlimit() would have raised the
maximum limit value, and the calling process does not have
appropriate privileges.
The setrlimit() function may fail if:
EINVAL The limit specified cannot be lowered because current usage
is already higher than the limit.
The following sections are informative.
None.
If a process attempts to set the hard limit or soft limit for
RLIMIT_NOFILE to less than the value of {_POSIX_OPEN_MAX} from
<limits.h>, unexpected behavior may occur.
If a process attempts to set the hard limit or soft limit for
RLIMIT_NOFILE to less than the highest currently open file
descriptor +1, unexpected behavior may occur.
It should be noted that RLIMIT_STACK applies ``at least'' to the
stack of the initial thread in the process, and not to the sum of
all the stacks in the process, as that would be very limiting
unless the value is so big as to provide no value at all with a
single thread.
None.
exec(1p), fork(3p), malloc(3p), open(3p), sigaltstack(3p),
sysconf(3p), ulimit(3p)
The Base Definitions volume of POSIX.1‐2017, stropts.h(0p),
sys_resource.h(0p)
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 GETRLIMIT(3P)
Pages that refer to this page: sys_resource.h(0p), exec(3p), fclose(3p), fflush(3p), fputc(3p), fseek(3p), malloc(3p), setrlimit(3p), ulimit(3p), write(3p), limits.conf(5)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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