GETRLIMIT(2) FreeBSD System Calls Manual GETRLIMIT(2)
NAME
getrlimit, setrlimit - control maximum system resource consumption
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>
int
getrlimit(int resource, struct rlimit *rlp);
int
setrlimit(int resource, const struct rlimit *rlp);
DESCRIPTION
Limits on the consumption of system resources by the current process and
each process it creates may be obtained with the getrlimit() system call,
and set with the setrlimit() system call.
The resource argument is one of the following:
RLIMIT_AS The maximum amount (in bytes) of virtual memory the
process is allowed to map.
RLIMIT_CORE The largest size (in bytes) core(5) file that may be
created.
RLIMIT_CPU The maximum amount of cpu time (in seconds) to be used by
each process.
RLIMIT_DATA The maximum size (in bytes) of the data segment for a
process; this defines how far a program may extend its
break with the sbrk(2) function.
RLIMIT_FSIZE The largest size (in bytes) file that may be created.
RLIMIT_KQUEUES The maximum number of kqueues this user id is allowed to
create.
RLIMIT_MEMLOCK The maximum size (in bytes) which a process may lock into
memory using the mlock(2) system call.
RLIMIT_NOFILE The maximum number of open files for this process.
RLIMIT_NPROC The maximum number of simultaneous processes for this
user id.
RLIMIT_NPTS The maximum number of pseudo-terminals this user id is
allowed to create.
RLIMIT_RSS When there is memory pressure and swap is available,
prioritize eviction of a process' resident pages beyond
this amount (in bytes). When memory is not under
pressure, this rlimit is effectively ignored. Even when
there is memory pressure, the amount of available swap
space and some sysctl settings like vm.swap_enabled and
vm.swap_idle_enabled can affect what happens to processes
that have exceeded this size.
Processes that exceed their set RLIMIT_RSS are not
signalled or halted. The limit is merely a hint to the
VM daemon to prefer to deactivate pages from processes
that have exceeded their set RLIMIT_RSS.
RLIMIT_SBSIZE The maximum size (in bytes) of socket buffer usage for
this user. This limits the amount of network memory, and
hence the amount of mbufs, that this user may hold at any
time.
RLIMIT_STACK The maximum size (in bytes) of the stack segment for a
process; this defines how far a program's stack segment
may be extended. Stack extension is performed
automatically by the system.
RLIMIT_SWAP The maximum size (in bytes) of the swap space that may be
reserved or used by all of this user id's processes.
This limit is enforced only if bit 1 of the vm.overcommit
sysctl is set. Please see tuning(7) for a complete
description of this sysctl.
RLIMIT_VMEM An alias for RLIMIT_AS.
A resource limit is specified as a soft limit and a hard limit. When a
soft limit is exceeded, a process might or might not receive a signal.
For example, signals are generated when the cpu time or file size is
exceeded, but not if the address space or RSS limit is exceeded. A
program that exceeds the soft limit is allowed to continue execution
until it reaches the hard limit, or modifies its own resource limit.
Even reaching the hard limit does not necessarily halt a process. For
example, if the RSS hard limit is exceeded, nothing happens.
The rlimit structure is used to specify the hard and soft limits on a
resource.
struct rlimit {
rlim_t rlim_cur; /* current (soft) limit */
rlim_t rlim_max; /* maximum value for rlim_cur */
};
Only the super-user may raise the maximum limits. Other users may only
alter rlim_cur within the range from 0 to rlim_max or (irreversibly)
lower rlim_max.
An "infinite" value for a limit is defined as RLIM_INFINITY.
Because this information is stored in the per-process information, this
system call must be executed directly by the shell if it is to affect all
future processes created by the shell; limit is thus a built-in command
to csh(1).
The system refuses to extend the data or stack space when the limits
would be exceeded in the normal way: a brk(2) function fails if the data
space limit is reached. When the stack limit is reached, the process
receives a segmentation fault (SIGSEGV); if this signal is not caught by
a handler using the signal stack, this signal will kill the process.
A file I/O operation that would create a file larger that the process'
soft limit will cause the write to fail and a signal SIGXFSZ to be
generated; this normally terminates the process, but may be caught. When
the soft cpu time limit is exceeded, a SIGXCPU signal is sent to the
offending process.
When most operations would allocate more virtual memory than allowed by
the soft limit of RLIMIT_AS, the operation fails with ENOMEM and no
signal is raised. A notable exception is stack extension, described
above. If stack extension would allocate more virtual memory than
allowed by the soft limit of RLIMIT_AS, a SIGSEGV signal will be
delivered. The caller is free to raise the soft address space limit up
to the hard limit and retry the allocation.
RETURN VALUES
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.
ERRORS
The getrlimit() and setrlimit() system calls will fail if:
[EFAULT] The address specified for rlp is invalid.
[EPERM] The limit specified to setrlimit() would have raised
the maximum limit value, and the caller is not the
super-user.
SEE ALSO
csh(1), quota(1), quotactl(2), sigaction(2), sigaltstack(2), sysctl(3),
ulimit(3)
HISTORY
The getrlimit() system call appeared in 4.2BSD.
FreeBSD 13.1-RELEASE-p6 September 30, 2016 FreeBSD 13.1-RELEASE-p6
man2web Home...