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RedHat 9 (Linux i386) - man page for setrlimit (redhat section 2)

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

       getrlimit, getrusage, setrlimit - get/set resource limits and usage

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

       int getrlimit(int resource, struct rlimit *rlim);
       int getrusage(int who, struct rusage *usage);
       int setrlimit(int resource, const struct rlimit *rlim);

       getrlimit  and  setrlimit  get and set resource limits respectively.  Each resource has an
       associated soft and hard limit, as defined by the rlimit structure (the rlim  argument  to
       both getrlimit() and setrlimit()):

	    struct rlimit {
		rlim_t rlim_cur;   /* Soft limit */
		rlim_t rlim_max;   /* Hard limit (ceiling
				      for rlim_cur) */

       The  soft limit is the value that the kernel enforces for the corresponding resource.  The
       hard limit acts as a ceiling for the soft limit: an unprivileged process may only set  its
       soft  limit  to a value in the range from 0 up to the hard limit, and (irreversibly) lower
       its hard limit.	A privileged process may make arbitrary changes to either limit value.

       The value RLIM_INFINITY denotes no limit on a resource (both in the structure returned  by
       getrlimit() and in the structure passed to setrlimit()).

       resource must be one of:

	      CPU  time  limit in seconds.  When the process reaches the soft limit, it is sent a
	      SIGXCPU signal.  The default action for this signal is to  terminate  the  process.
	      However,	the  signal can be caught, and the handler can return control to the main
	      program.	If the process continues to consume CPU time, it  will	be  sent  SIGXCPU
	      once  per second until the hard limit is reached, at which time it is sent SIGKILL.
	      (This latter point describes Linux 2.2 and 2.4 behaviour.  Implementations vary  in
	      how they treat processes which continue to consume CPU time after reaching the soft
	      limit.  Portable applications that need to catch	this  signal  should  perform  an
	      orderly termination upon first receipt of SIGXCPU.)

	      The  maximum  size  of  the process's data segment (initialized data, uninitialized
	      data, and heap).	This limit affects calls to brk() and sbrk(), which fail with the
	      error ENOMEM upon encountering the soft limit of this resource.

	      The  maximum  size of files that the process may create.	Attempts to extend a file
	      beyond this limit result in delivery of a SIGXFSZ signal.  By default, this  signal
	      terminates  a  process,  but a process can catch this signal instead, in which case
	      the relevant system call (e.g., write(), truncate()) fails with the error EFBIG.

	      A limit on the combined number of  flock()  locks  and  fcntl()  leases  that  this
	      process may establish (Linux 2.4 and later).

	      The  maximum  number  of	bytes of virtual memory that may be locked into RAM using
	      mlock() and mlockall().

	      Specifies a value one greater than the maximum file descriptor number that  can  be
	      opened  by  this	process.   Attempts (open(), pipe(), dup(), etc.)  to exceed this
	      limit yield the error EMFILE.

	      The maximum number of processes that can be created for the real	user  ID  of  the
	      calling process.	Upon encountering this limit, fork() fails with the error EAGAIN.

	      Specifies the limit (in pages) of the process's resident set (the number of virtual
	      pages resident in RAM).  This limit only has effect  in  Linux  2.4  onwatrds,  and
	      there only affects calls to madvise() specifying MADVISE_WILLNEED.

	      The  maximum  size  of  the  process  stack, in bytes.  Upon reaching this limit, a
	      SIGSEGV signal is generated.  To handle this  signal,  a	process  must  employ  an
	      alternate signal stack (sigaltstack(2)).

       RLIMIT_OFILE is the BSD name for RLIMIT_NOFILE.

       getrusage  returns  the	current  resource  usages,  for  a  who  of either RUSAGE_SELF or
       RUSAGE_CHILDREN.  The former asks for resources used by the current  process,  the  latter
       for resources used by those of its children that have terminated and have been waited for.

	    struct rusage {
		struct timeval ru_utime; /* user time used */
		struct timeval ru_stime; /* system time used */
		long   ru_maxrss;	 /* maximum resident set size */
		long   ru_ixrss;	 /* integral shared memory size */
		long   ru_idrss;	 /* integral unshared data size */
		long   ru_isrss;	 /* integral unshared stack size */
		long   ru_minflt;	 /* page reclaims */
		long   ru_majflt;	 /* page faults */
		long   ru_nswap;	 /* swaps */
		long   ru_inblock;	 /* block input operations */
		long   ru_oublock;	 /* block output operations */
		long   ru_msgsnd;	 /* messages sent */
		long   ru_msgrcv;	 /* messages received */
		long   ru_nsignals;	 /* signals received */
		long   ru_nvcsw;	 /* voluntary context switches */
		long   ru_nivcsw;	 /* involuntary context switches */

       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

       EFAULT rlim or usage points outside the accessible address space.

       EINVAL getrlimit or setrlimit is called with a bad resource, or getrusage is called with a
	      bad who.

       EPERM  A non-superuser tries to use setrlimit() to increase the soft or hard  limit  above
	      the  current  hard  limit, or a superuser tries to increase RLIMIT_NOFILE above the
	      current kernel maximum.

       SVr4, BSD 4.3

       Including <sys/time.h> is not required these days, but  increases  portability.	 (Indeed,
       struct timeval is defined in <sys/time.h>.)

       On  Linux,  if  the  disposition  of SIGCHLD is set to SIG_IGN then the resource usages of
       child processes are automatically included  in  the  value  returned  by  RUSAGE_CHILDREN,
       although POSIX 1003.1-2001 explicitly prohibits this.

       The  above struct was taken from BSD 4.3 Reno.  Not all fields are meaningful under Linux.
       Right now (Linux 2.4) only  the	fields	ru_utime,  ru_stime,  ru_minflt,  ru_majflt,  and
       ru_nswap are maintained.

       dup(2),	fcntl(2), fork(2), mlock(2), mlockall(2), mmap(2), open(2), quotactl(2), sbrk(2),
       wait3(2), wait4(2), malloc(3), ulimit(3), signal(7)

Linux					    2002-07-09				     GETRLIMIT(2)

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