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GETRLIMIT(2)		       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 cre-
		     ated.

     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  al-
		     lowed to create.

     RLIMIT_PIPEBUF  The  maximum  total size of in-kernel buffers for bi-direc-
		     tional pipes/fifos that this user id is allowed to consume.
		     The buffers for kernel FIFOs created on the first open of a
		     filesystem object created by (mkfifo(2)) are  also  charged
		     to  the  user  ID of the process opening it, not the FIFO's
		     filesystem owner.	Despite somewhat unexpected, this is  in
		     fact fair, since user of the fifo is not necessary its cre-
		     ator.

     RLIMIT_RSS      When there is memory pressure and swap is available, prior-
		     itize  eviction  of  a  process' resident pages beyond this
		     amount (in bytes).  When memory is not under pressure, this
		     rlimit is effectively ignored.

		     Processes that exceed their set  RLIMIT_RSS  are  not  sig-
		     nalled  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_UMTXP    The  limit of the number of process-shared posix thread li-
		     brary objects allocated by user id.

     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  ex-
     ceeds  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  re-
     source.

	   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 al-
     ter  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 us-
     ing 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 allo-
     cation.

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 ports 15.quarterly	  July 25, 2024 		    GETRLIMIT(2)

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