.\" Copyright (c) 1992 Drew Eckhardt, March 28, 1992

.\" and Copyright (c) 2002, 2004, 2005, 2008, 2010 Michael Kerrisk

.\"

.\" %%%LICENSE_START(VERBATIM)

.\" 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.\" manual page may be incorrect or out-of-date.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.

.\" %%%LICENSE_END

.\"

.\" Modified by Michael Haardt <michael@moria.de>

.\" Modified 1993-07-23 by Rik Faith <faith@cs.unc.edu>

.\" Modified 1996-01-13 by Arnt Gulbrandsen <agulbra@troll.no>

.\" Modified 1996-01-22 by aeb, following a remark by

.\"          Tigran Aivazian <tigran@sco.com>

.\" Modified 1996-04-14 by aeb, following a remark by

.\"          Robert Bihlmeyer <robbe@orcus.ping.at>

.\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>

.\" Modified 2001-05-04 by aeb, following a remark by

.\"          Håvard Lygre <hklygre@online.no>

.\" Modified 2001-04-17 by Michael Kerrisk <mtk.manpages@gmail.com>

.\" Modified 2002-06-13 by Michael Kerrisk <mtk.manpages@gmail.com>

.\"     Added note on nonstandard behavior when SIGCHLD is ignored.

.\" Modified 2002-07-09 by Michael Kerrisk <mtk.manpages@gmail.com>

.\"	Enhanced descriptions of 'resource' values

.\" 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 <mtk.manpages@gmail.com>

.\"     Added notes on CAP_SYS_RESOURCE

.\"

.\" 2004-11-16 -- mtk: the getrlimit.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

.\" 2005-07-13, mtk, documented RLIMIT_MSGQUEUE limit.

.\" 2005-07-28, mtk, Added descriptions of RLIMIT_NICE and RLIMIT_RTPRIO

.\" 2008-05-07, mtk / Peter Zijlstra, Added description of RLIMIT_RTTIME

.\" 2010-11-06, mtk: Added documentation of prlimit()

.\"

.TH GETRLIMIT 2 2017-09-15 "Linux" "Linux Programmer's Manual"

.SH NAME

getrlimit, setrlimit, prlimit \- get/set resource limits

.SH SYNOPSIS

.B #include <sys/time.h>

.br

.B #include <sys/resource.h>

.PP

.BI "int getrlimit(int " resource ", struct rlimit *" rlim );

.br

.BI "int setrlimit(int " resource ", const struct rlimit *" rlim );

.PP

.BI "int prlimit(pid_t "  pid ", int " resource \

", const struct rlimit *" new_limit ,

.br

.BI "            struct rlimit *" old_limit );

.PP

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.PP

.BR prlimit ():

_GNU_SOURCE

.SH DESCRIPTION

The

.BR getrlimit ()

and

.BR setrlimit ()

system calls get and set resource limits respectively.

Each resource has an associated soft and hard limit, as defined by the

.I rlimit

structure:

.PP

.in +4n

.EX

struct rlimit {

    rlim_t rlim_cur;  /* Soft limit */

    rlim_t rlim_max;  /* Hard limit (ceiling for rlim_cur) */

};

.EE

.in

.PP

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 set only 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

The

.I resource

argument must be one of:

.TP

.B RLIMIT_AS

This is the maximum size of the process's virtual memory

(address space).

The limit is specified in bytes, and is rounded down to the system page size.

.\" 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.

In addition, automatic stack expansion fails

(and generates a

.B SIGSEGV

that kills the process if no alternate stack

has been made available via

.BR sigaltstack (2)).

Since the value is a \fIlong\fP, on machines with a 32-bit \fIlong\fP

either this limit is at most 2\ GiB, or this resource is unlimited.

.TP

.B RLIMIT_CORE

This is the maximum size of a

.I core

file (see

.BR core (5))

in bytes that the process may dump.

When 0 no core dump files are created.

When nonzero, larger dumps are truncated to this size.

.TP

.B RLIMIT_CPU

This is a limit, in seconds,

on the amount of CPU time that the process can consume.

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 behavior.

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

This is the maximum size

of the process's data segment (initialized data,

uninitialized data, and heap).

The limit is specified in bytes, and is rounded down to the system page size.

This limit affects calls to

.BR brk (2),

.BR sbrk (2),

and (since Linux 4.7)

.BR mmap (2),

.\" commits 84638335900f1995495838fe1bd4870c43ec1f67

.\" ("mm: rework virtual memory accounting"),

.\" f4fcd55841fc9e46daac553b39361572453c2b88

.\" (mm: enable RLIMIT_DATA by default with workaround for valgrind).

which fail with the error

.B ENOMEM

upon encountering the soft limit of this resource.

.TP

.B RLIMIT_FSIZE

This is the maximum size in bytes 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 (2),

.BR truncate (2))

fails with the error

.BR EFBIG .

.TP

.BR RLIMIT_LOCKS " (early Linux 2.4 only)"

.\" to be precise: Linux 2.4.0-test9; no longer in 2.4.25 / 2.5.65

This is a limit on the combined number of

.BR flock (2)

locks and

.BR fcntl (2)

leases that this process may establish.

.TP

.B RLIMIT_MEMLOCK

This is the maximum number of bytes of memory that may be locked

into RAM.

This limit is in effect rounded down to the nearest multiple

of the system page size.

This limit affects

.BR mlock (2),

.BR 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),

.BR mlockall (2),

and

.BR mmap (2)

.BR MAP_LOCKED ;

a process can lock bytes up to this limit in each of these

two categories.

.IP

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.

.TP

.BR RLIMIT_MSGQUEUE " (since Linux 2.6.8)"

This is a limit on the number of bytes that can be allocated

for POSIX message queues for the real user ID of the calling process.

This limit is enforced for

.BR mq_open (3).

Each message queue that the user creates counts (until it is removed)

against this limit according to the formula:

.IP

    Since Linux 3.5:

.IP

.EX

        bytes = attr.mq_maxmsg * sizeof(struct msg_msg) +

                min(attr.mq_maxmsg, MQ_PRIO_MAX) *

                      sizeof(struct posix_msg_tree_node)+

                                /* For overhead */

                attr.mq_maxmsg * attr.mq_msgsize;

                                /* For message data */

.EE

.IP

    Linux 3.4 and earlier:

.IP

.EX

        bytes = attr.mq_maxmsg * sizeof(struct msg_msg *) +

                                /* For overhead */

                attr.mq_maxmsg * attr.mq_msgsize;

                                /* For message data */

.EE

.IP

where

.I attr

is the

.I mq_attr

structure specified as the fourth argument to

.BR mq_open (3),

and the

.I msg_msg

and

.I posix_msg_tree_node

structures are kernel-internal structures.

.IP

The "overhead" addend in the formula accounts for overhead

bytes required by the implementation

and ensures that the user cannot

create an unlimited number of zero-length messages (such messages

nevertheless each consume some system memory for bookkeeping overhead).

.TP

.BR RLIMIT_NICE " (since Linux 2.6.12, but see BUGS below)"

This specifies a ceiling to which the process's nice value can be raised using

.BR setpriority (2)

or

.BR nice (2).

The actual ceiling for the nice value is calculated as

.IR "20\ \-\ rlim_cur" .

The useful range for this limit is thus from 1

(corresponding to a nice value of 19) to 40

(corresponding to a nice value of -20).

This unusual choice of range was necessary

because negative numbers cannot be specified

as resource limit values, since they typically have special meanings.

For example,

.B RLIM_INFINITY

typically is the same as \-1.

For more detail on the nice value, see

.BR sched (7).

.TP

.B RLIMIT_NOFILE

This specifies a value one greater than the maximum file descriptor number

that can be opened by this process.

Attempts

.RB ( open (2),

.BR pipe (2),

.BR dup (2),

etc.)

to exceed this limit yield the error

.BR EMFILE .

(Historically, this limit was named

.B RLIMIT_OFILE

on BSD.)

.IP

Since Linux 4.5,

this limit also defines the maximum number of file descriptors that

an unprivileged process (one without the

.BR CAP_SYS_RESOURCE

capability) may have "in flight" to other processes,

by being passed across UNIX domain sockets.

This limit applies to the

.BR sendmsg (2)

system call.

For further details, see

.BR unix (7).

.TP

.B RLIMIT_NPROC

This is a limit on the number of extant process

(or, more precisely on Linux, threads)

for the real user ID of the calling process.

So long as the current number of processes belonging to this

process's real user ID is greater than or equal to this limit,

.BR fork (2)

fails with the error

.BR EAGAIN .

.IP

The

.B RLIMIT_NPROC

limit is not enforced for processes that have either the

.B CAP_SYS_ADMIN

or the

.B CAP_SYS_RESOURCE

capability.

.TP

.B RLIMIT_RSS

This is a limit (in bytes) on the process's resident set

(the number of virtual pages resident in RAM).

This limit has effect only in Linux 2.4.x, x < 30, and there

affects only calls to

.BR madvise (2)

specifying

.BR MADV_WILLNEED .

.\" As at kernel 2.6.12, this limit still does nothing in 2.6 though

.\" talk of making it do something has surfaced from time to time in LKML

.\"       -- MTK, Jul 05

.TP

.BR RLIMIT_RTPRIO " (since Linux 2.6.12, but see BUGS)"

This specifies a ceiling on the real-time priority that may be set for

this process using

.BR sched_setscheduler (2)

and

.BR sched_setparam (2).

.IP

For further details on real-time scheduling policies, see

.BR sched (7)

.TP

.BR RLIMIT_RTTIME " (since Linux 2.6.25)"

This is a limit (in microseconds)

on the amount of CPU time that a process scheduled

under a real-time scheduling policy may consume without making a blocking

system call.

For the purpose of this limit,

each time a process makes a blocking system call,

the count of its consumed CPU time is reset to zero.

The CPU time count is not reset if the process continues trying to

use the CPU but is preempted, its time slice expires, or it calls

.BR sched_yield (2).

.IP

Upon reaching the soft limit, the process is sent a

.B SIGXCPU

signal.

If the process catches or ignores this signal and

continues consuming CPU time, then

.B SIGXCPU

will be generated once each second until the hard limit is reached,

at which point the process is sent a

.B SIGKILL

signal.

.IP

The intended use of this limit is to stop a runaway

real-time process from locking up the system.

.IP

For further details on real-time scheduling policies, see

.BR sched (7)

.TP

.BR RLIMIT_SIGPENDING " (since Linux 2.6.8)"

This is a 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 enforced only for

.BR sigqueue (3);

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.

.\" 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

This is 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)).

.IP

Since Linux 2.6.23,

this limit also determines the amount of space used for the process's

command-line arguments and environment variables; for details, see

.BR execve (2).

.SS prlimit()

.\" commit c022a0acad534fd5f5d5f17280f6d4d135e74e81

.\" Author: Jiri Slaby <jslaby@suse.cz>

.\" Date:   Tue May 4 18:03:50 2010 +0200

.\"

.\"     rlimits: implement prlimit64 syscall

.\"

.\" commit 6a1d5e2c85d06da35cdfd93f1a27675bfdc3ad8c

.\" Author: Jiri Slaby <jslaby@suse.cz>

.\" Date:   Wed Mar 24 17:06:58 2010 +0100

.\"

.\"     rlimits: add rlimit64 structure

.\"

The Linux-specific

.BR prlimit ()

system call combines and extends the functionality of

.BR setrlimit ()

and

.BR getrlimit ().

It can be used to both set and get the resource limits of an arbitrary process.

.PP

The

.I resource

argument has the same meaning as for

.BR setrlimit ()

and

.BR getrlimit ().

.PP

If the

.IR new_limit

argument is a not NULL, then the

.I rlimit

structure to which it points is used to set new values for

the soft and hard limits for

.IR resource .

If the

.IR old_limit

argument is a not NULL, then a successful call to

.BR prlimit ()

places the previous soft and hard limits for

.I resource

in the

.I rlimit

structure pointed to by

.IR old_limit .

.PP

The

.I pid

argument specifies the ID of the process on which the call is to operate.

If

.I pid

is 0, then the call applies to the calling process.

To set or get the resources of a process other than itself,

the caller must have the

.B CAP_SYS_RESOURCE

capability in the user namespace of the process

whose resource limits are being changed, or the

real, effective, and saved set user IDs of the target process

must match the real user ID of the caller

.I and

the real, effective, and saved set group IDs of the target process

must match the real group ID of the caller.

.\" FIXME . this permission check is strange

.\" Asked about this on LKML, 7 Nov 2010

.\"     "Inconsistent credential checking in prlimit() syscall"

.SH RETURN VALUE

On success, these system calls return 0.

On error, \-1 is returned, and

.I errno

is set appropriately.

.SH ERRORS

.TP

.B EFAULT

A pointer argument points to a location

outside the accessible address space.

.TP

.B EINVAL

The value specified in

.I resource

is not valid;

or, for

.BR setrlimit ()

or

.BR prlimit ():

.I rlim\->rlim_cur

was greater than

.IR rlim\->rlim_max .

.TP

.B EPERM

An unprivileged process tried to raise the hard limit; the

.B CAP_SYS_RESOURCE

capability is required to do this.

.TP

.B EPERM

The caller tried to increase the hard

.B RLIMIT_NOFILE

limit above the maximum defined by

.IR /proc/sys/fs/nr_open

(see

.BR proc (5))

.TP

.B EPERM

.RB ( prlimit ())

The calling process did not have permission to set limits

for the process specified by

.IR pid .

.TP

.B ESRCH

Could not find a process with the ID specified in

.IR pid .

.SH VERSIONS

The

.BR prlimit ()

system call is available since Linux 2.6.36.

Library support is available since glibc 2.13.

.SH ATTRIBUTES

For an explanation of the terms used in this section, see

.BR attributes (7).

.TS

allbox;

lbw35 lb lb

l l l.

Interface	Attribute	Value

T{

.BR getrlimit (),

.BR setrlimit (),

.BR prlimit ()

T}	Thread safety	MT-Safe

.TE

.sp 1

.SH CONFORMING TO

.BR getrlimit (),

.BR setrlimit ():

POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

.PP

.BR prlimit ():

Linux-specific.

.PP

.B RLIMIT_MEMLOCK

and

.B RLIMIT_NPROC

derive from BSD and are not specified in POSIX.1;

they are present on the BSDs and Linux, but on few other implementations.

.B RLIMIT_RSS

derives from BSD and is not specified in POSIX.1;

it is nevertheless present on most implementations.

.BR RLIMIT_MSGQUEUE ,

.BR RLIMIT_NICE ,

.BR RLIMIT_RTPRIO ,

.BR RLIMIT_RTTIME ,

and

.B RLIMIT_SIGPENDING

are Linux-specific.

.SH NOTES

A child process created via

.BR fork (2)

inherits its parent's resource limits.

Resource limits are preserved across

.BR execve (2).

.PP

Lowering the soft limit for a resource below the process's

current consumption of that resource will succeed

(but will prevent the process from further increasing

its consumption of the resource).

.PP

One can set the resource limits of the shell using the built-in

.IR ulimit

command

.RI ( limit

in

.BR csh (1)).

The shell's resource limits are inherited by the processes that

it creates to execute commands.

.PP

Since Linux 2.6.24, the resource limits of any process can be inspected via

.IR /proc/[pid]/limits ;

see

.BR proc (5).

.PP

Ancient systems provided a

.BR vlimit ()

function with a similar purpose to

.BR setrlimit ().

For backward compatibility, glibc also provides

.BR vlimit ().

All new applications should be written using

.BR setrlimit ().

.SS C library/kernel ABI differences

Since version 2.13, the glibc

.BR getrlimit ()

and

.BR setrlimit ()

wrapper functions no longer invoke the corresponding system calls,

but instead employ

.BR prlimit (),

for the reasons described in BUGS.

.PP

The name of the glibc wrapper function is

.BR prlimit ();

the underlying system call is

.BR prlimit64 ().

.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.

.PP

In 2.6.x kernels before 2.6.17, a

.B RLIMIT_CPU

limit of 0 is wrongly treated as "no limit" (like

.BR RLIM_INFINITY ).

Since Linux 2.6.17, setting a limit of 0 does have an effect,

but is actually treated as a limit of 1 second.

.\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=114008066530167&w=2

.PP

A kernel bug means that

.\" See https://lwn.net/Articles/145008/

.B RLIMIT_RTPRIO

does not work in kernel 2.6.12; the problem is fixed in kernel 2.6.13.

.PP

In kernel 2.6.12, there was an off-by-one mismatch

between the priority ranges returned by

.BR getpriority (2)

and

.BR RLIMIT_NICE .

This had the effect that the actual ceiling for the nice value

was calculated as

.IR "19\ \-\ rlim_cur" .

This was fixed in kernel 2.6.13.

.\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=112256338703880&w=2

.PP

Since Linux 2.6.12,

.\" The relevant patch, sent to LKML, seems to be

.\" http://thread.gmane.org/gmane.linux.kernel/273462

.\" From: Roland McGrath <roland <at> redhat.com>

.\" Subject: [PATCH 7/7] make RLIMIT_CPU/SIGXCPU per-process

.\" Date: 2005-01-23 23:27:46 GMT

if a process reaches its soft

.BR RLIMIT_CPU

limit and has a handler installed for

.BR SIGXCPU ,

then, in addition to invoking the signal handler,

the kernel increases the soft limit by one second.

This behavior repeats if the process continues to consume CPU time,

until the hard limit is reached,

at which point the process is killed.

Other implementations

.\" Tested Solaris 10, FreeBSD 9, OpenBSD 5.0

do not change the

.BR RLIMIT_CPU

soft limit in this manner,

and the Linux behavior is probably not standards conformant;

portable applications should avoid relying on this Linux-specific behavior.

.\" FIXME . https://bugzilla.kernel.org/show_bug.cgi?id=50951

The Linux-specific

.BR RLIMIT_RTTIME

limit exhibits the same behavior when the soft limit is encountered.

.PP

Kernels before 2.4.22 did not diagnose the error

.B EINVAL

for

.BR setrlimit ()

when

.I rlim\->rlim_cur

was greater than

.IR rlim\->rlim_max .

.\"

.SS Representation of """large""" resource limit values on 32-bit platforms

The glibc

.BR getrlimit ()

and

.BR setrlimit ()

wrapper functions use a 64-bit

.IR rlim_t

data type, even on 32-bit platforms.

However, the

.I rlim_t

data type used in the

.BR getrlimit ()

and

.BR setrlimit ()

system calls is a (32-bit)

.IR "unsigned long" .

Furthermore, in Linux versions before 2.6.36,

the kernel represents resource limits on 32-bit platforms as

.IR "unsigned long" .

However, a 32-bit data type is not wide enough.

.\" https://bugzilla.kernel.org/show_bug.cgi?id=5042

.\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=12201

The most pertinent limit here is

.BR RLIMIT_FSIZE ,

which specifies the maximum size to which a file can grow:

to be useful, this limit must be represented using a type

that is as wide as the type used to

represent file offsets\(emthat is, as wide as a 64-bit

.BR off_t

(assuming a program compiled with

.IR _FILE_OFFSET_BITS=64 ).

.PP

To work around this kernel limitation,

if a program tried to set a resource limit to a value larger than

can be represented in a 32-bit

.IR "unsigned long" ,

then the glibc

.BR setrlimit ()

wrapper function silently converted the limit value to

.BR RLIM_INFINITY .

In other words, the requested resource limit setting was silently ignored.

.PP

This problem was addressed in Linux 2.6.36 with two principal changes:

.IP * 3

the addition of a new kernel representation of resource limits that

uses 64 bits, even on 32-bit platforms;

.IP *

the addition of the

.BR prlimit ()

system call, which employs 64-bit values for its resource limit arguments.

.PP

Since version 2.13,

.\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=12201

glibc works around the limitations of the

.BR getrlimit ()

and

.BR setrlimit ()

system calls by implementing

.BR setrlimit ()

and

.BR getrlimit ()

as wrapper functions that call

.BR prlimit ().

.SH EXAMPLE

The program below demonstrates the use of

.BR prlimit ().

.PP

.EX

#define _GNU_SOURCE

#define _FILE_OFFSET_BITS 64

#include <stdio.h>

#include <time.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/resource.h>

#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \\

                        } while (0)

int

main(int argc, char *argv[])

{

    struct rlimit old, new;

    struct rlimit *newp;

    pid_t pid;

    if (!(argc == 2 || argc == 4)) {

        fprintf(stderr, "Usage: %s <pid> [<new\-soft\-limit> "

                "<new\-hard\-limit>]\\n", argv[0]);

        exit(EXIT_FAILURE);

    }

    pid = atoi(argv[1]);        /* PID of target process */

    newp = NULL;

    if (argc == 4) {

        new.rlim_cur = atoi(argv[2]);

        new.rlim_max = atoi(argv[3]);

        newp = &new;

    }

    /* Set CPU time limit of target process; retrieve and display

       previous limit */

    if (prlimit(pid, RLIMIT_CPU, newp, &old) == \-1)

        errExit("prlimit\-1");

    printf("Previous limits: soft=%lld; hard=%lld\\n",

            (long long) old.rlim_cur, (long long) old.rlim_max);

    /* Retrieve and display new CPU time limit */

    if (prlimit(pid, RLIMIT_CPU, NULL, &old) == \-1)

        errExit("prlimit\-2");

    printf("New limits: soft=%lld; hard=%lld\\n",

            (long long) old.rlim_cur, (long long) old.rlim_max);

    exit(EXIT_SUCCESS);

}

.EE

.SH SEE ALSO

.BR prlimit (1),

.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 malloc (3),

.BR sigqueue (3),

.BR ulimit (3),

.BR core (5),

.BR capabilities (7),

.BR cgroups (7),

.BR credentials (7),

.BR signal (7)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.