.\" Hey Emacs! This file is -*- nroff -*- source. .\" .\" Copyright (c) 1992 Drew Eckhardt, March 28, 1992 .\" Copyright (c) 2002 Michael Kerrisk .\" .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" .\" Modified by Michael Haardt .\" Modified 1993-07-23 by Rik Faith .\" Modified 1996-01-13 by Arnt Gulbrandsen .\" Modified 1996-01-22 by aeb, following a remark by .\" Tigran Aivazian .\" Modified 1996-04-14 by aeb, following a remark by .\" Robert Bihlmeyer .\" Modified 1996-10-22 by Eric S. Raymond .\" Modified 2001-05-04 by aeb, following a remark by .\" Håvard Lygre .\" Modified 2001-04-17 by Michael Kerrisk .\" Modified 2002-06-13 by Michael Kerrisk .\" Added note on non-standard behaviour when SIGCHLD is ignored. .\" Modified 2002-07-09 by Michael Kerrisk .\" Enhanced descriptions of 'resource' values for [gs]etrlimit() .\" Modified 2003-11-28 by aeb, added RLIMIT_CORE .\" Modified 2004-03-26 by aeb, added RLIMIT_AS .\" Modified 2004-06-16 by Michael Kerrisk .\" Added notes on CAP_SYS_RESOURCE .\" .\" 2004-11-16 -- mtk: the gerlimit.2 page, which formally included .\" coverage of getrusage(2), has been split, so that the latter .\" is now covered in its own getrusage.2. .\" .\" Modified 2004-11-16, mtk: A few other minor changes .\" Modified 2004-11-23, mtk .\" Added notes on RLIMIT_MEMLOCK, RLIMIT_NPROC, and RLIMIT_RSS .\" to "CONFORMING TO" .\" Modified 2004-11-25, mtk .\" Rewrote discussion on RLIMIT_MEMLOCK to incorporate kernel .\" 2.6.9 changes. .\" Added note on RLIMIT_CPU error in older kernels .\" 2004-11-03, mtk .\" Added RLIMIT_SIGPENDING .\" .TH GETRLIMIT 2 2004-06-16 "Linux" "Linux Programmer's Manual" .SH NAME getrlimit, setrlimit \- get/set resource limits .SH SYNOPSIS .B #include .br .B #include .sp .BI "int getrlimit(int " resource ", struct rlimit *" rlim ); .br .BI "int setrlimit(int " resource ", const struct rlimit *" rlim ); .SH DESCRIPTION .BR getrlimit () and .BR setrlimit () get and set resource limits respectively. Each resource has an associated soft and hard limit, as defined by the .B rlimit structure (the .I rlim argument to both .BR getrlimit "() and " setrlimit ()): .PP .in +0.5i .nf struct rlimit { rlim_t rlim_cur; /* Soft limit */ rlim_t rlim_max; /* Hard limit (ceiling for rlim_cur) */ }; .fi .in -0.5i The soft limit is the value that the kernel enforces for the corresponding resource. The hard limit acts as a ceiling for the soft limit: an unprivileged process may only set its soft limit to a value in the range from 0 up to the hard limit, and (irreversibly) lower its hard limit. A privileged process (under Linux: one with the .B CAP_SYS_RESOURCE capability) may make arbitrary changes to either limit value. .PP The value .B RLIM_INFINITY denotes no limit on a resource (both in the structure returned by .BR getrlimit () and in the structure passed to .BR setrlimit ()). .PP .I resource must be one of: .TP .B RLIMIT_AS The maximum size of the process's virtual memory (address space) in bytes. .\" since 2.0.27 / 2.1.12 This limit affects calls to .BR brk (2), .BR mmap (2) and .BR mremap (2), which fail with the error .B ENOMEM upon exceeding this limit. Also automatic stack expansion will fail (and generate a .B SIGSEGV that kills the process if no alternate stack has been made available via .BR sigaltstack (2)). Since the value is a long, on machines with a 32-bit long either this limit is at most 2 GiB, or this resource is unlimited. .TP .B RLIMIT_CORE Maximum size of .I core file. When 0 no core dump files are created. When non-zero, larger dumps are truncated to this size. .TP .B RLIMIT_CPU CPU time limit in seconds. When the process reaches the soft limit, it is sent a .B SIGXCPU signal. The default action for this signal is to terminate the process. However, the signal can be caught, and the handler can return control to the main program. If the process continues to consume CPU time, it will be sent .B SIGXCPU once per second until the hard limit is reached, at which time it is sent .BR SIGKILL . (This latter point describes Linux 2.2 through 2.6 behaviour. Implementations vary in how they treat processes which continue to consume CPU time after reaching the soft limit. Portable applications that need to catch this signal should perform an orderly termination upon first receipt of .BR SIGXCPU .) .TP .B RLIMIT_DATA The maximum size of the process's data segment (initialized data, uninitialized data, and heap). This limit affects calls to .BR brk "() and " sbrk (), which fail with the error .B ENOMEM upon encountering the soft limit of this resource. .TP .B RLIMIT_FSIZE The maximum size of files that the process may create. Attempts to extend a file beyond this limit result in delivery of a .B SIGXFSZ signal. By default, this signal terminates a process, but a process can catch this signal instead, in which case the relevant system call (e.g., .BR write "(), " truncate ()) fails with the error .BR EFBIG . .TP .B RLIMIT_LOCKS A limit on the combined number of .BR flock () locks and .BR fcntl() leases that this process may establish. (Early Linux 2.4 only.) .\" to be precise: Linux 2.4.0-test9; no longer in 2.4.25 / 2.5.65 .TP .B RLIMIT_MEMLOCK The maximum number of bytes of memory that may be locked into RAM. In effect this limit is rounded down to the nearest multiple of the system page size. This limit affects .BR mlock "(2) and " mlockall (2) and the .BR mmap (2) .B MAP_LOCKED operation. Since Linux 2.6.9 it also affects the .BR shmctl (2) .B SHM_LOCK operation, where it sets a maximum on the total bytes in shared memory segments (see .BR shmget (2)) that may be locked by the real user ID of the calling process. The .BR shmctl (2) .B SHM_LOCK locks are accounted for separately from the per-process memory locks established by .BR mlock "(2), " mlockall (2), and .BR mmap (2) .BR MAP_LOCKED ; a process can lock bytes up to this limit in each of these two categories. In Linux kernels before 2.6.9, this limit controlled the amount of memory that could be locked by a privileged process. Since Linux 2.6.9, no limits are placed on the amount of memory that a privileged process may lock, and this limit instead governs the amount of memory that an unprivileged process may lock. .\" FIXME Linux 2.6.8 adds RLIMIT_MSGQUEUE .TP .B RLIMIT_NOFILE Specifies a value one greater than the maximum file descriptor number that can be opened by this process. Attempts .RB ( open "(), " pipe "(), " dup "(), etc.)" to exceed this limit yield the error .BR EMFILE . .TP .B RLIMIT_NPROC The maximum number of processes that can be created for the real user ID of the calling process. Upon encountering this limit, .BR fork () fails with the error .BR EAGAIN . .TP .B RLIMIT_RSS Specifies the limit (in pages) of the process's resident set (the number of virtual pages resident in RAM). This limit only has effect in Linux 2.4.x, and there only affects calls to .BR madvise () specifying .BR MADVISE_WILLNEED . .\" As at kernel 2.6.9, this limit still does nothing in 2.6 though .\" talk of making it do something continues in LKML -- MTK, Nov 04 .TP .B RLIMIT_SIGPENDING Specifies the limit on the number of signals that may be queued for the real user ID of the calling process. Both standard and real-time signals are counted for the purpose of checking this limit. However, the limit is only enforced for .BR sigqueue (2); it is always possible to use .BR kill (2) to queue one instance of any of the signals that are not already queued to the process. (Since Linux 2.6.8.) .\" This replaces the /proc/sys/kernel/rtsig-max system-wide limit .\" that was present in kernels <= 2.6.7. MTK Dec 04 .TP .B RLIMIT_STACK The maximum size of the process stack, in bytes. Upon reaching this limit, a .B SIGSEGV signal is generated. To handle this signal, a process must employ an alternate signal stack .RB ( sigaltstack (2)). .PP .B RLIMIT_OFILE is the BSD name for .BR RLIMIT_NOFILE . .SH "RETURN VALUE" On success, zero is returned. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS .TP .B EFAULT .I rlim points outside the accessible address space. .TP .B EINVAL .I resource is not valid. .TP .B EPERM An unprivileged process tried to use \fBsetrlimit()\fP to increase a soft or hard limit above the current hard limit; the .B CAP_SYS_RESOURCE capability is required to do this. Or, the process tried to use \fBsetrlimit()\fP to increase the soft or hard RLIMIT_NOFILE limit above the current kernel maximum (NR_OPEN). .SH BUGS In older Linux kernels, the .B SIGXCPU and .B SIGKILL signals delivered when a process encountered the soft and hard .B RLIMIT_CPU limits were delivered one (CPU) second later than they should have been. This was fixed in kernel 2.6.8. .SH "CONFORMING TO" SVr4, BSD 4.3. .BR RLIMIT_MEMLOCK and .BR RLIMIT_NPROC derive from BSD and are not specified in POSIX.1-2001; they are present on the BSDs and Linux, but on few other implementations. .BR RLIMIT_RSS derives from BSD and is not specified in POSIX.1-2001; it is nevertheless present on most implementations. .B RLIMIT_SIGPENDING is Linux specific. .\" FIXME RLIMIT_MSGQUEUE is also Linux specific. .SH "SEE ALSO" .BR dup (2), .BR fcntl (2), .BR fork (2), .BR getrusage (2), .BR mlock (2), .BR mmap (2), .BR open (2), .BR quotactl (2), .BR sbrk (2), .BR shmctl (2), .BR sigqueue (2), .BR malloc (3), .BR ulimit (3), .BR capabilities (7), .BR signal (7)