getrlimit(2) — AIX PS/2 1.2.1



GETRLIMIT(2,L)              AIX Technical Reference              GETRLIMIT(2,L)



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getrlimit, setrlimit, vlimit



PURPOSE

Controls maximum system resource consumption.

SYNTAX

#include <sys/time.h>
#include <sys/resource.h>



                getrlimit (resource, rlp)   setrlimit (resource, rlp)
                int resource;               int resource;
                struct rlimit *rlp;         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_CPU   The maximum amount of CPU time (in seconds) to be used by each
             process.

RLIMIT_FSIZE The largest size, in bytes, of any single file that may be
             created.

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
             system call.

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_CORE  The largest size, in bytes, of a core file that may be created.

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.




Processed November 7, 1990      GETRLIMIT(2,L)                                1



GETRLIMIT(2,L)              AIX Technical Reference              GETRLIMIT(2,L)



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
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 {
     long rlim_cur; /*current(soft)limit*/
     long rlim_max; /*hard limit*/
  };

Only the superuser 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 (0x7fffffff).

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.

The system refuses to extend the data or stack space when the limits would be
exceeded in the normal way; a break call 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.

When the soft CPU time limit is exceeded, a signal SIGXCPU is sent to the
offending process.

COMPATIBILITY NOTE

To maintain upward compatibility with older BSD programs, the vlimit interface
is also supported.  It is used by compiling with the Berkeley Compatibility
Library (libbsd.a).  Its syntax is as follows:

#include <sys/vlimit.h>

vlimit (resource, value)
int resource, value;

The flags for the resource parameter are defined in sys/vlimit.h, and are
mapped to corresponding flags for setrlimit.  The value parameter is an integer
which is used as a hard limit parameter to setrlimit.

RETURN VALUE

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

ERROR CONDITIONS




Processed November 7, 1990      GETRLIMIT(2,L)                                2



GETRLIMIT(2,L)              AIX Technical Reference              GETRLIMIT(2,L)



The possible errors are:

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 superuser.

RELATED INFORMATION

In this book:  "setquota," "sigaction, sigvec, signal," and "sigstack."

The csh command in AIX Operating System Commands Reference.











































Processed November 7, 1990      GETRLIMIT(2,L)                                3

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