getrlimit(2) - NetBSD Manual Pages

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


NAME

     getrlimit, setrlimit - control maximum system resource consumption


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() call, and
     set with the setrlimit() call.

     The resource parameter is one of the following:

     RLIMIT_CORE     The largest size (in bytes) core file that may be creat-
                     ed.

     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) system call.

     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) function.

     RLIMIT_NOFILE   The maximum number of open files for this process.

     RLIMIT_NPROC    The maximum number of simultaneous processes for this us-
                     er 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 pro-
                     cesses that are exceeding their declared resident set
                     size.

     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 automati-
                     cally by the system.

     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 contin-
     ue 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;       /* hard limit */
           };

     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) low-
     er 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) call fails if the data
     space limit is reached.  When the stack limit is reached, the process re-
     ceives 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 gener-
     ated; this normally terminates the process, but may be caught.  When the
     soft cpu time limit is exceeded, a signal SIGXCPU is sent to the offend-
     ing process.


RETURN VALUES

     A 0 return value indicates that the call succeeded, changing or returning
     the resource limit.   A return value of -1 indicates that an error oc-
     curred, and an error code is stored in the global location errno.


ERRORS

     getrlimit() and setrlimit() 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), sh(1), quotactl(2), sigaction(2), sigaltstack(2), sysctl(3)


HISTORY

     The getrlimit() function call appeared in 4.2BSD.

NetBSD 1.4                       June 4, 1993                                2