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getrlimit(2)		      System Calls Manual		  getrlimit(2)

NAME
       getrlimit, setrlimit - control maximum system resource consumption

SYNOPSIS
       #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 a variety of system	resources by a process
       and each	process	it creates may be obtained with	 getrlimit()  and  set
       with setrlimit().

       Each  call  to  either getrlimit() or setrlimit() identifies a specific
       resource	to be operated upon as well as a resource limit.   A  resource
       limit  is  a  pair of values:  one specifying the current (soft)	limit,
       the other a maximum (hard) limit.  Soft limits  may  be	changed	 by  a
       process	to  any	value that is less than	or equal to the	hard limit.  A
       process may (irreversibly) lower	its hard limit to any  value  that  is
       greater than or equal to	the soft limit.	 Only a	process	with an	effec-
       tive user ID of super-user can raise a hard limit.  Both	hard and  soft
       limits  can  be	changed	in a single call to setrlimit()	subject	to the
       constraints described above.  Limits may	have an	 "infinite"  value  of
       RLIM_INFINITY.	rlp  is	 a  pointer to struct rlimit that includes the
       following members:
	    rlim_t rlim_cur; /*	current	(soft) limit */
	    rlim_t rlim_max; /*	hard limit */

       rlim_t is an arithmetic data type to which objects of type int, size_t,
       and off_t can be	cast without loss of information.

       The  possible resources,	their descriptions, and	the actions taken when
       the current limit is exceeded are summarized in the table below:

       RLIMIT_CORE	   The maximum size of a core file in bytes  that  may
			   be created by a process.  A limit of	0 will prevent
			   the creation	of a core file.

			   The writing of a core file will terminate  at  this
			   size.

       RLIMIT_CPU	   The maximum amount of CPU time in seconds used by a
			   process.  This is a soft limit only.

			   SIGXCPU is sent to the process.  If the process  is
			   holding or ignoring SIGXCPU,	the behavior is	sched-
			   uling class defined.

       RLIMIT_DATA	   The maximum size of a process's heap	in bytes.

			   brk(2) will fail with errno set to ENOMEM.

       RLIMIT_FSIZE	   The maximum size of a file in  bytes	 that  may  be
			   created  by	a  process.  A limit of	0 will prevent
			   the creation	of a file.

			   SIGXFSZ is sent to the process.  If the process  is
			   holding  or ignoring	SIGXFSZ, continued attempts to
			   increase the	size of	a file beyond the  limit  will
			   fail	with errno set to EFBIG.

       RLIMIT_NOFILE	   One more than the maximum value that	the system may
			   assign to a newly created descriptor.   This	 limit
			   constrains  the  number  of file descriptors	that a
			   process may create.

       RLIMIT_STACK	   The maximum size of a  process's  stack  in	bytes.
			   The	system	will  not automatically	grow the stack
			   beyond this limit.

			   SIGSEGV is sent to the process.  If the process  is
			   holding or ignoring SIGSEGV,	or is catching SIGSEGV
			   and has not made arrangements to use	 an  alternate
			   stack  (see	sigaltstack(2)),  the  disposition  of
			   SIGSEGV will	be set to SIG_DFL before it is sent.

       RLIMIT_VMEM	   The maximum size  of	 a  process's  mapped  address
			   space in bytes.

			   brk(2)  and	mmap(2)	functions will fail with errno
			   set to ENOMEM.  In addition,	 the  automatic	 stack
			   growth will fail with the effects outlined above.

       Because limit information is stored in the per-process information, the
       shell builtin ulimit command must directly execute this system call  if
       it is to	affect all future processes created by the shell.

       The  value of the current limit of the following	resources affect these
       implementation defined parameters:

	    Limit	   Implementation Defined Constant
	    RLIMIT_FSIZE   FCHR_MAX
	    RLIMIT_NOFILE  OPEN_MAX

RETURN VALUES
       Upon successful completion, the function	getrlimit() returns a value of
       0;  otherwise,  it  returns a value of -1 and sets errno	to indicate an
       error.

ERRORS
       Under the following conditions, the  functions  getrlimit()  and	 setr-
       limit() fail and	set errno to:

       EFAULT rlp points to an illegal address.

       EINVAL An invalid resource was specified; or in a setrlimit() call, the
	      new rlim_cur exceeds the new rlim_max.

       EPERM  The limit	specified to setrlimit() would have raised the maximum
	      limit  value,  and  the effective	user of	the calling process is
	      not super-user.

SEE ALSO
       brk(2), open(2),	sigaltstack(2),	malloc(3C), signal(3C),	signal(5)

NOTES
       RLIMIT_STACK:
	    Within a process setrlimit(), will increase	the limit on the  size
	    of	your stack, but	will not move current memory segments to allow
	    for	that growth.  Therefore, to guarantee that the	process	 stack
	    can	 grow to the limit, you	must alter the limit prior to the exe-
	    cution of the process in which the new stack size is to be used.

				  25 Jan 1995			  getrlimit(2)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | NOTES

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