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  current  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 terminate at this size.

       RLIMIT_CPU
              This is the maximum amount of CPU time, in seconds, used by a process.  If this limit is exceeded,
              SIGXCPU 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 arrangements to use an alternate stack, the  disposition  of  SIGSEGV  shall  be  set  to
              SIG_DFL before it is generated.

       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 corresponding saved soft limit; otherwise, the new limit shall be the  requested  value.  In
       addition,  if the corresponding 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
       implementation-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,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications 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  Standard,  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(P)