GETRLIMIT(2)	    UNIX Programmer's Manual	     GETRLIMIT(2)


NAME
     getrlimit, setrlimit - control maximum system resource con-
     sumption

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

     getrlimit(resource, rlp)
     int resource;
     struct rlimit *rlp;

     setrlimit(resource, rlp)
     int resource;
     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.

     The resource parameter is one of the following:

     RLIMIT_CPU       the maximum amount of cpu time (in seconds)
		      to be used by each process.

     RLIMIT_FSIZE     the largest size, in bytes, of any single
		      file that may be created.

     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_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_CORE      the largest size, in bytes, of a core file
		      that may be created.

     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 processes that are exceeding
		      their declared resident set size.


Printed 11/26/99	  May 13, 1986				1


GETRLIMIT(2)	    UNIX Programmer's Manual	     GETRLIMIT(2)


     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 is exceeded), but it
     will be allowed to continue 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 {
	       int  rlim_cur; /* current (soft) limit */
	       int  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
     (0x7fffffff).

     Because this information is stored in the per-process infor-
     mation, 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 break call
     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 that is too
     large will cause a signal SIGXFSZ to be generated; this nor-
     mally terminates the process, but may be caught.  When the
     soft cpu time limit is exceeded, a signal SIGXCPU is sent to
     the offending process.

RETURN VALUE
     A 0 return value indicates that the call succeeded, changing
     or returning the resource limit.	A return value of -1
     indicates that an error occurred, and an error code is
     stored in the global location errno.

ERRORS
     The possible errors are:

     [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.


Printed 11/26/99	  May 13, 1986				2


GETRLIMIT(2)	    UNIX Programmer's Manual	     GETRLIMIT(2)


SEE ALSO
     csh(1), quota(2), sigvec(2), sigstack(2)

BUGS
     There should be limit and unlimit commands in sh(1) as well
     as in csh.


Printed 11/26/99	  May 13, 1986				3


 
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