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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), sigvec(2), sysctl(3),
     ulimit(3)

HISTORY

     The getrlimit() system call appeared in 4.2BSD.