1 .\" Copyright (c) 1992 Drew Eckhardt, March 28, 1992
2 .\" and Copyright (c) 2002, 2004, 2005, 2008, 2010 Michael Kerrisk
4 .\" %%%LICENSE_START(VERBATIM)
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
26 .\" Modified by Michael Haardt <michael@moria.de>
27 .\" Modified 1993-07-23 by Rik Faith <faith@cs.unc.edu>
28 .\" Modified 1996-01-13 by Arnt Gulbrandsen <agulbra@troll.no>
29 .\" Modified 1996-01-22 by aeb, following a remark by
30 .\" Tigran Aivazian <tigran@sco.com>
31 .\" Modified 1996-04-14 by aeb, following a remark by
32 .\" Robert Bihlmeyer <robbe@orcus.ping.at>
33 .\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
34 .\" Modified 2001-05-04 by aeb, following a remark by
35 .\" HÃ¥vard Lygre <hklygre@online.no>
36 .\" Modified 2001-04-17 by Michael Kerrisk <mtk.manpages@gmail.com>
37 .\" Modified 2002-06-13 by Michael Kerrisk <mtk.manpages@gmail.com>
38 .\" Added note on nonstandard behavior when SIGCHLD is ignored.
39 .\" Modified 2002-07-09 by Michael Kerrisk <mtk.manpages@gmail.com>
40 .\" Enhanced descriptions of 'resource' values
41 .\" Modified 2003-11-28 by aeb, added RLIMIT_CORE
42 .\" Modified 2004-03-26 by aeb, added RLIMIT_AS
43 .\" Modified 2004-06-16 by Michael Kerrisk <mtk.manpages@gmail.com>
44 .\" Added notes on CAP_SYS_RESOURCE
46 .\" 2004-11-16 -- mtk: the getrlimit.2 page, which formally included
47 .\" coverage of getrusage(2), has been split, so that the latter
48 .\" is now covered in its own getrusage.2.
50 .\" Modified 2004-11-16, mtk: A few other minor changes
51 .\" Modified 2004-11-23, mtk
52 .\" Added notes on RLIMIT_MEMLOCK, RLIMIT_NPROC, and RLIMIT_RSS
53 .\" to "CONFORMING TO"
54 .\" Modified 2004-11-25, mtk
55 .\" Rewrote discussion on RLIMIT_MEMLOCK to incorporate kernel
57 .\" Added note on RLIMIT_CPU error in older kernels
58 .\" 2004-11-03, mtk, Added RLIMIT_SIGPENDING
59 .\" 2005-07-13, mtk, documented RLIMIT_MSGQUEUE limit.
60 .\" 2005-07-28, mtk, Added descriptions of RLIMIT_NICE and RLIMIT_RTPRIO
61 .\" 2008-05-07, mtk / Peter Zijlstra, Added description of RLIMIT_RTTIME
62 .\" 2010-11-06, mtk: Added documentation of prlimit()
64 .TH GETRLIMIT 2 2014-05-28 "Linux" "Linux Programmer's Manual"
66 getrlimit, setrlimit, prlimit \- get/set resource limits
68 .B #include <sys/time.h>
70 .B #include <sys/resource.h>
72 .BI "int getrlimit(int " resource ", struct rlimit *" rlim );
74 .BI "int setrlimit(int " resource ", const struct rlimit *" rlim );
76 .BI "int prlimit(pid_t " pid ", int " resource \
77 ", const struct rlimit *" new_limit ,
79 .BI " struct rlimit *" old_limit );
82 Feature Test Macro Requirements for glibc (see
83 .BR feature_test_macros (7)):
87 _GNU_SOURCE && _FILE_OFFSET_BITS == 64
93 system calls get and set resource limits respectively.
94 Each resource has an associated soft and hard limit, as defined by the
101 rlim_t rlim_cur; /* Soft limit */
102 rlim_t rlim_max; /* Hard limit (ceiling for rlim_cur) */
107 The soft limit is the value that the kernel enforces for the
108 corresponding resource.
109 The hard limit acts as a ceiling for the soft limit:
110 an unprivileged process may set only its soft limit to a value in the
111 range from 0 up to the hard limit, and (irreversibly) lower its hard limit.
112 A privileged process (under Linux: one with the
114 capability) may make arbitrary changes to either limit value.
118 denotes no limit on a resource (both in the structure returned by
120 and in the structure passed to
125 argument must be one of:
128 The maximum size of the process's virtual memory (address space) in bytes.
129 .\" since 2.0.27 / 2.1.12
130 This limit affects calls to
135 which fail with the error
137 upon exceeding this limit.
138 Also automatic stack expansion will fail
141 that kills the process if no alternate stack
142 has been made available via
143 .BR sigaltstack (2)).
144 Since the value is a \fIlong\fP, on machines with a 32-bit \fIlong\fP
145 either this limit is at most 2 GiB, or this resource is unlimited.
151 When 0 no core dump files are created.
152 When nonzero, larger dumps are truncated to this size.
155 CPU time limit in seconds.
156 When the process reaches the soft limit, it is sent a
159 The default action for this signal is to terminate the process.
160 However, the signal can be caught, and the handler can return control to
162 If the process continues to consume CPU time, it will be sent
164 once per second until the hard limit is reached, at which time
167 (This latter point describes Linux behavior.
168 Implementations vary in how they treat processes which continue to
169 consume CPU time after reaching the soft limit.
170 Portable applications that need to catch this signal should
171 perform an orderly termination upon first receipt of
175 The maximum size of the process's data segment (initialized data,
176 uninitialized data, and heap).
177 This limit affects calls to
181 which fail with the error
183 upon encountering the soft limit of this resource.
186 The maximum size of files that the process may create.
187 Attempts to extend a file beyond this limit result in delivery of a
190 By default, this signal terminates a process, but a process can
191 catch this signal instead, in which case the relevant system call (e.g.,
197 .BR RLIMIT_LOCKS " (Early Linux 2.4 only)"
198 .\" to be precise: Linux 2.4.0-test9; no longer in 2.4.25 / 2.5.65
199 A limit on the combined number of
203 leases that this process may establish.
206 The maximum number of bytes of memory that may be locked
208 In effect this limit is rounded down to the nearest multiple
209 of the system page size.
218 Since Linux 2.6.9 it also affects the
221 operation, where it sets a maximum on the total bytes in
222 shared memory segments (see
224 that may be locked by the real user ID of the calling process.
228 locks are accounted for separately from the per-process memory
235 a process can lock bytes up to this limit in each of these
237 In Linux kernels before 2.6.9, this limit controlled the amount of
238 memory that could be locked by a privileged process.
239 Since Linux 2.6.9, no limits are placed on the amount of memory
240 that a privileged process may lock, and this limit instead governs
241 the amount of memory that an unprivileged process may lock.
243 .BR RLIMIT_MSGQUEUE " (since Linux 2.6.8)"
244 Specifies the limit on the number of bytes that can be allocated
245 for POSIX message queues for the real user ID of the calling process.
246 This limit is enforced for
248 Each message queue that the user creates counts (until it is removed)
249 against this limit according to the formula:
252 bytes = attr.mq_maxmsg * sizeof(struct msg_msg *) +
253 attr.mq_maxmsg * attr.mq_msgsize
260 structure specified as the fourth argument to
263 The first addend in the formula, which includes
264 .I "sizeof(struct msg_msg\ *)"
265 (4 bytes on Linux/i386), ensures that the user cannot
266 create an unlimited number of zero-length messages (such messages
267 nevertheless each consume some system memory for bookkeeping overhead).
269 .BR RLIMIT_NICE " (since Linux 2.6.12, but see BUGS below)"
270 Specifies a ceiling to which the process's nice value can be raised using
274 The actual ceiling for the nice value is calculated as
275 .IR "20\ \-\ rlim_cur" .
276 (This strangeness occurs because negative numbers cannot be specified
277 as resource limit values, since they typically have special meanings.
280 typically is the same as \-1.)
283 Specifies a value one greater than the maximum file descriptor number
284 that can be opened by this process.
290 to exceed this limit yield the error
292 (Historically, this limit was named
297 The maximum number of processes (or, more precisely on Linux, threads)
298 that can be created for the real user ID of the calling process.
299 Upon encountering this limit,
303 This limit is not enforced for processes that have either the
310 Specifies the limit (in pages) of the process's resident set
311 (the number of virtual pages resident in RAM).
312 This limit has effect only in Linux 2.4.x, x < 30, and there
313 affects only calls to
317 .\" As at kernel 2.6.12, this limit still does nothing in 2.6 though
318 .\" talk of making it do something has surfaced from time to time in LKML
321 .BR RLIMIT_RTPRIO " (since Linux 2.6.12, but see BUGS)"
322 Specifies a ceiling on the real-time priority that may be set for
324 .BR sched_setscheduler (2)
326 .BR sched_setparam (2).
328 .BR RLIMIT_RTTIME " (since Linux 2.6.25)"
329 Specifies a limit (in microseconds)
330 on the amount of CPU time that a process scheduled
331 under a real-time scheduling policy may consume without making a blocking
333 For the purpose of this limit,
334 each time a process makes a blocking system call,
335 the count of its consumed CPU time is reset to zero.
336 The CPU time count is not reset if the process continues trying to
337 use the CPU but is preempted, its time slice expires, or it calls
340 Upon reaching the soft limit, the process is sent a
343 If the process catches or ignores this signal and
344 continues consuming CPU time, then
346 will be generated once each second until the hard limit is reached,
347 at which point the process is sent a
351 The intended use of this limit is to stop a runaway
352 real-time process from locking up the system.
354 .BR RLIMIT_SIGPENDING " (since Linux 2.6.8)"
355 Specifies the limit on the number of signals
356 that may be queued for the real user ID of the calling process.
357 Both standard and real-time signals are counted for the purpose of
359 However, the limit is enforced only for
361 it is always possible to use
363 to queue one instance of any of the signals that are not already
364 queued to the process.
365 .\" This replaces the /proc/sys/kernel/rtsig-max system-wide limit
366 .\" that was present in kernels <= 2.6.7. MTK Dec 04
369 The maximum size of the process stack, in bytes.
370 Upon reaching this limit, a
373 To handle this signal, a process must employ an alternate signal stack
374 .RB ( sigaltstack (2)).
377 this limit also determines the amount of space used for the process's
378 command-line arguments and environment variables; for details, see
381 .\" commit c022a0acad534fd5f5d5f17280f6d4d135e74e81
382 .\" Author: Jiri Slaby <jslaby@suse.cz>
383 .\" Date: Tue May 4 18:03:50 2010 +0200
386 system call combines and extends the functionality of
390 It can be used to both set and get the resource limits of an arbitrary process.
394 argument has the same meaning as for
401 argument is a not NULL, then the
403 structure to which it points is used to set new values for
404 the soft and hard limits for
408 argument is a not NULL, then a successful call to
410 places the previous soft and hard limits for
414 structure pointed to by
419 argument specifies the ID of the process on which the call is to operate.
422 is 0, then the call applies to the calling process.
423 To set or get the resources of a process other than itself,
424 the caller must have the
427 real, effective, and saved set user IDs of the target process
428 must match the real user ID of the caller
430 the real, effective, and saved set group IDs of the target process
431 must match the real group ID of the caller.
432 .\" FIXME this permission check is strange
433 .\" Asked about this on LKML, 7 Nov 2010
434 .\" "Inconsistent credential checking in prlimit() syscall"
436 On success, these system calls return 0.
437 On error, \-1 is returned, and
439 is set appropriately.
443 A pointer argument points to a location
444 outside the accessible address space.
447 The value specified in
456 .IR rlim\->rlim_max .
459 An unprivileged process tried to raise the hard limit; the
461 capability is required to do this.
462 Or, the caller tried to increase the hard
464 limit above the current kernel maximum
466 Or, the calling process did not have permission to set limits
467 for the process specified by
471 Could not find a process with the ID specified in
476 system call is available since Linux 2.6.36.
477 Library support is available since glibc 2.13.
481 SVr4, 4.3BSD, POSIX.1-2001.
489 derive from BSD and are not specified in POSIX.1-2001;
490 they are present on the BSDs and Linux, but on few other implementations.
492 derives from BSD and is not specified in POSIX.1-2001;
493 it is nevertheless present on most implementations.
494 .BR RLIMIT_MSGQUEUE ,
502 A child process created via
504 inherits its parent's resource limits.
505 Resource limits are preserved across
508 Lowering the soft limit for a resource below the process's
509 current consumption of that resource will succeed
510 (but will prevent the process from further increasing
511 its consumption of the resource).
513 One can set the resource limits of the shell using the built-in
519 The shell's resource limits are inherited by the processes that
520 it creates to execute commands.
522 Since Linux 2.6.24, the resource limits of any process can be inspected via
523 .IR /proc/[pid]/limits ;
527 Ancient systems provided a
529 function with a similar purpose to
531 For backward compatibility, glibc also provides
533 All new applications should be written using
536 .\" FIXME prlimit() does not suffer
537 .\" https://bugzilla.kernel.org/show_bug.cgi?id=5042
538 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=12201
539 .\" Since versions 2.13, glibc has library implementations of
540 .\" getrlimit() and setrlimit() that use prlimit() to work around
542 In older Linux kernels, the
546 signals delivered when a process encountered the soft and hard
548 limits were delivered one (CPU) second later than they should have been.
549 This was fixed in kernel 2.6.8.
551 In 2.6.x kernels before 2.6.17, a
553 limit of 0 is wrongly treated as "no limit" (like
555 Since Linux 2.6.17, setting a limit of 0 does have an effect,
556 but is actually treated as a limit of 1 second.
557 .\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=114008066530167&w=2
559 A kernel bug means that
560 .\" See https://lwn.net/Articles/145008/
562 does not work in kernel 2.6.12; the problem is fixed in kernel 2.6.13.
564 In kernel 2.6.12, there was an off-by-one mismatch
565 between the priority ranges returned by
569 This had the effect that the actual ceiling for the nice value
571 .IR "19\ \-\ rlim_cur" .
572 This was fixed in kernel 2.6.13.
573 .\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=112256338703880&w=2
576 .\" The relevant patch, sent to LKML, seems to be
577 .\" http://thread.gmane.org/gmane.linux.kernel/273462
578 .\" From: Roland McGrath <roland <at> redhat.com>
579 .\" Subject: [PATCH 7/7] make RLIMIT_CPU/SIGXCPU per-process
580 .\" Date: 2005-01-23 23:27:46 GMT
581 if a process reaches its soft
583 limit and has a handler installed for
585 then, in addition to invoking the signal handler,
586 the kernel increases the soft limit by one second.
587 This behavior repeats if the process continues to consume CPU time,
588 until the hard limit is reached,
589 at which point the process is killed.
590 Other implementations
591 .\" Tested Solaris 10, FreeBSD 9, OpenBSD 5.0
594 soft limit in this manner,
595 and the Linux behavior is probably not standards conformant;
596 portable applications should avoid relying on this Linux-specific behavior.
597 .\" FIXME https://bugzilla.kernel.org/show_bug.cgi?id=50951
600 limit exhibits the same behavior when the soft limit is encountered.
602 Kernels before 2.4.22 did not diagnose the error
609 .IR rlim\->rlim_max .
611 The program below demonstrates the use of
616 #define _FILE_OFFSET_BITS 64
621 #include <sys/resource.h>
623 #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \\
627 main(int argc, char *argv[])
629 struct rlimit old, new;
633 if (!(argc == 2 || argc == 4)) {
634 fprintf(stderr, "Usage: %s <pid> [<new\-soft\-limit> "
635 "<new\-hard\-limit>]\\n", argv[0]);
639 pid = atoi(argv[1]); /* PID of target process */
643 new.rlim_cur = atoi(argv[2]);
644 new.rlim_max = atoi(argv[3]);
648 /* Set CPU time limit of target process; retrieve and display
651 if (prlimit(pid, RLIMIT_CPU, newp, &old) == \-1)
652 errExit("prlimit\-1");
653 printf("Previous limits: soft=%lld; hard=%lld\\n",
654 (long long) old.rlim_cur, (long long) old.rlim_max);
656 /* Retrieve and display new CPU time limit */
658 if (prlimit(pid, RLIMIT_CPU, NULL, &old) == \-1)
659 errExit("prlimit\-2");
660 printf("New limits: soft=%lld; hard=%lld\\n",
661 (long long) old.rlim_cur, (long long) old.rlim_max);
682 .BR capabilities (7),
685 This page is part of release 3.68 of the Linux
688 A description of the project,
689 information about reporting bugs,
690 and the latest version of this page,
692 \%http://www.kernel.org/doc/man\-pages/.