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GETRLIMIT(2)		    BSD	System Calls Manual		  GETRLIMIT(2)

NAME
     getrlimit,	setrlimit -- control maximum system resource consumption

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #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() call,	and
     set with the setrlimit() call.  Resources of an arbitrary process can be
     obtained/changed using sysctl(3).

     The resource parameter 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 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) system call.

     RLIMIT_FSIZE    The largest size (in bytes) file that may be created.

     RLIMIT_MEMLOCK  The maximum size (in bytes) which a process may lock into
		     memory using the mlock(2) function.

     RLIMIT_NOFILE   The maximum number	of open	files for this process.

     RLIMIT_NPROC    The maximum number	of simultaneous	processes for this
		     user id.

     RLIMIT_RSS	     The maximum size (in bytes) to which a process's resident
		     set size may grow.	 This imposes a	limit on the amount of
		     physical memory to	be given to a process; if memory is
		     tight, the	system will prefer to take memory from pro-
		     cesses that are exceeding their declared resident set
		     size.

     RLIMIT_SBSIZE   The maximum size (in bytes) of the	socket buffers set by
		     the setsockopt(2) SO_RCVBUF and SO_SNDBUF options.

     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 automati-
		     cally by the system.

     A resource	limit is specified as a	soft limit and a hard limit.  When a
     soft limit	is exceeded a process may receive a signal (for	example, if
     the CPU time or file size is exceeded), but it will be allowed to con-
     tinue execution until it reaches the hard limit (or modifies its resource
     limit).  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;	   /* hard limit */
	   };

     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.  Thus, shells provide built-in
     commands to change	the limits (limit for csh(1), or ulimit	for sh(1)).

     The system	refuses	to extend the data or stack space when the limits
     would be exceeded in the normal way: a brk(2) call	fails if the data
     space limit is reached.  When the stack limit is reached, the process re-
     ceives 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	gener-
     ated; this	normally terminates the	process, but may be caught.  When the
     soft CPU time limit is exceeded, a	signal SIGXCPU is sent to the offend-
     ing process.

RETURN VALUES
     A 0 return	value indicates	that the call succeeded, changing or returning
     the resource limit.  Otherwise, -1	is returned and	the global variable
     errno is set to indicate the error.

ERRORS
     The getrlimit() and setrlimit() will fail if:

     [EFAULT]		The address specified for rlp is invalid.

     [EINVAL]		Specified resource was invalid;	or, in the setrlimit()
			call, the specified rlim_cur exceeds the specified
			rlim_max.

     [EPERM]		The limit specified to setrlimit() would have raised
			the maximum limit value, and the caller	is not the su-
			per-user.

     The setrlimit() function may fail if:

     [EINVAL]		The limit specified to setrlimit() cannot be lowered,
			because	current	usage is already higher	than the
			limit.

SEE ALSO
     csh(1), sh(1), mlock(2), setsockopt(2), sigaction(2), sigaltstack(2),
     libquota(3), sysctl(3)

HISTORY
     The getrlimit() function call appeared in 4.2BSD.

BUGS
     The resource limit	RLIMIT_RSS is not implemented in uvm(9)	which means
     that process memory size limits are not enforced.

BSD			       November	15, 2011			   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | BUGS

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