xenial (2) setrlimit.2freebsd.gz

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.