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.

Debian                                           August 20, 2008                                    GETRLIMIT(2)