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 created.

     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_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_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.

     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_NPTS     The maximum number of pseudo-terminals created by this user id.

     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 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 {
                   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 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;
     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 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 generated; this normally 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 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), sigaltstack(2), sigaction(2), sysctl(3), ulimit(3)

HISTORY

     The getrlimit() system call appeared in 4.2BSD.