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GETRLIMIT(3P)              POSIX Programmer's Manual             GETRLIMIT(3P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       getrlimit, setrlimit - control maximum resource consumption

SYNOPSIS
       #include <sys/resource.h>

       int getrlimit(int resource, struct rlimit *rlp);
       int setrlimit(int resource, const struct rlimit *rlp);


DESCRIPTION
       The  getrlimit()  function  shall  get,  and the setrlimit() function shall set, limits on the consumption of a
       variety of resources.

       Each call to either getrlimit() or setrlimit() identifies a specific resource to be operated upon as well as  a
       resource  limit. A resource limit is represented by an rlimit structure. The rlim_cur member specifies the cur-
       rent or soft limit and the rlim_max member specifies the maximum or hard limit. Soft limits may be changed by a
       process  to any value that is less than or equal to the hard limit. A process may (irreversibly) lower its hard
       limit to any value that is greater than or equal to the soft limit. Only a process with appropriate  privileges
       can raise a hard limit. Both hard and soft limits can be changed in a single call to setrlimit() subject to the
       constraints described above.

       The value RLIM_INFINITY, defined in <sys/resource.h>, shall be considered to be larger  than  any  other  limit
       value.  If  a  call  to getrlimit() returns RLIM_INFINITY for a resource, it means the implementation shall not
       enforce limits on that resource. Specifying RLIM_INFINITY as any resource limit value on a successful  call  to
       setrlimit() shall inhibit enforcement of that resource limit.

       The following resources are defined:

       RLIMIT_CORE
              This  is the maximum size of a core file, in bytes, that may be created by a process. A limit of 0 shall
              prevent the creation of a core file. If this limit is exceeded, the writing of a core file shall  termi-
              nate at this size.

       RLIMIT_CPU
              This is the maximum amount of CPU time, in seconds, used by a process.  If this limit is exceeded, SIGX-
              CPU shall be generated for the process. If the process is catching or ignoring SIGXCPU, or  all  threads
              belonging to that process are blocking SIGXCPU, the behavior is unspecified.

       RLIMIT_DATA
              This  is  the maximum size of a process' data segment, in bytes. If this limit is exceeded, the malloc()
              function shall fail with errno set to [ENOMEM].

       RLIMIT_FSIZE
              This is the maximum size of a file, in bytes, that may be created by a process. If a write  or  truncate
              operation  would  cause  this  limit  to be exceeded, SIGXFSZ shall be generated for the thread.  If the
              thread is blocking, or the process is catching or ignoring SIGXFSZ, continued attempts to  increase  the
              size of a file from end-of-file to beyond the limit shall fail with errno set to [EFBIG].

       RLIMIT_NOFILE
              This  is  a  number  one  greater  than  the maximum value that the system may assign to a newly-created
              descriptor. If this limit is exceeded, functions that allocate a file descriptor shall fail  with  errno
              set to [EMFILE]. This limit constrains the number of file descriptors that a process may allocate.

       RLIMIT_STACK
              This  is  the maximum size of a process' stack, in bytes. The implementation does not automatically grow
              the stack beyond this limit. If this limit is exceeded, SIGSEGV shall be generated for  the  thread.  If
              the thread is blocking SIGSEGV, or the process is ignoring or catching SIGSEGV and has not made arrange-
              ments to use an alternate stack, the disposition of SIGSEGV shall be set to SIG_DFL before it is  gener-
              ated.

       RLIMIT_AS
              This  is the maximum size of a process' total available memory, in bytes. If this limit is exceeded, the
              malloc() and mmap() functions shall fail with errno set to [ENOMEM]. In addition,  the  automatic  stack
              growth fails with the effects outlined above.


       When  using  the  getrlimit()  function,  if a resource limit can be represented correctly in an object of type
       rlim_t, then its representation is returned; otherwise, if the value of the resource limit is equal to that  of
       the  corresponding  saved hard limit, the value returned shall be RLIM_SAVED_MAX; otherwise, the value returned
       shall be RLIM_SAVED_CUR.

       When using the setrlimit() function, if the requested new limit is RLIM_INFINITY, the new limit  shall  be  "no
       limit'';  otherwise,  if  the  requested  new limit is RLIM_SAVED_MAX, the new limit shall be the corresponding
       saved hard limit; otherwise, if the requested new limit is RLIM_SAVED_CUR, the new limit shall  be  the  corre-
       sponding  saved  soft  limit; otherwise, the new limit shall be the requested value. In addition, if the corre-
       sponding saved limit can be represented correctly in an object of type rlim_t then it shall be overwritten with
       the new limit.

       The  result  of  setting  a  limit to RLIM_SAVED_MAX or RLIM_SAVED_CUR is unspecified unless a previous call to
       getrlimit() returned that value as the soft or hard limit for the corresponding resource limit.

       The determination of whether a limit can be correctly represented in an object of type  rlim_t  is  implementa-
       tion-defined.   For  example, some implementations permit a limit whose value is greater than RLIM_INFINITY and
       others do not.

       The exec family of functions shall cause resource limits to be saved.

RETURN VALUE
       Upon successful completion, getrlimit() and setrlimit() shall return 0. Otherwise, these functions shall return
       -1 and set errno to indicate the error.

ERRORS
       The getrlimit() and setrlimit() functions shall fail if:

       EINVAL An  invalid resource was specified; or in a setrlimit() call, the new rlim_cur exceeds the new rlim_max.

       EPERM  The limit specified to setrlimit() would have raised the maximum limit value, and  the  calling  process
              does not have appropriate privileges.


       The setrlimit() function may fail if:

       EINVAL The limit specified cannot be lowered because current usage is already higher than the limit.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       If  a  process  attempts  to  set  the  hard  limit  or  soft limit for RLIMIT_NOFILE to less than the value of
       {_POSIX_OPEN_MAX} from <limits.h>, unexpected behavior may occur.

       If a process attempts to set the hard limit or soft limit for RLIMIT_NOFILE to less than the highest  currently
       open file descriptor +1, unexpected behavior may occur.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       exec(),  fork(),  malloc(),  open(),  sigaltstack()  ,  sysconf(),  ulimit(),  the  Base  Definitions volume of
       IEEE Std 1003.1-2001, <stropts.h>, <sys/resource.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,  Inc  and  The
       Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                        GETRLIMIT(3P)