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GETRLIMIT(2)              FreeBSD System Calls Manual             GETRLIMIT(2)

     getrlimit, setrlimit - control maximum system resource consumption

     Standard C Library (libc, -lc)

     #include <sys/types.h>
     #include <sys/time.h>
     #include <sys/resource.h>

     getrlimit(int resource, struct rlimit *rlp);

     setrlimit(int resource, const struct rlimit *rlp);

     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

     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

     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

     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

           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.

     Upon successful completion, the value 0 is returned; otherwise the
     value -1 is returned and the global variable errno is set to indicate the

     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

     csh(1), quota(1), quotactl(2), sigaction(2), sigaltstack(2), sysctl(3),

     The getrlimit() system call appeared in 4.2BSD.

FreeBSD 11.1-RELEASE-p4       September 30, 2016       FreeBSD 11.1-RELEASE-p4
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