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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 differ (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 speci‐
       fies 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  consid‐
       ered  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  unspeci‐
		     fied.

       RLIMIT_DATA   This  is  the  maximum  size  of  a  data	segment of the
		     process, in bytes.	 If this limit is exceeded,  the  mal‐
		     loc() 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 the initial  thread's	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 catch‐
		     ing  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 total available memory of the
		     process, in bytes. If this limit is  exceeded,  the  mal‐
		     loc()  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 repre‐
       sented 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 cor‐
       responding 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	 addi‐
       tion,  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_INFIN‐
       ITY 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 <lim‐
       its.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
       It should be noted that RLIMIT_STACK applies ``at least'' to the	 stack
       of  the	initial	 thread	 in the process, and not to the sum of all the
       stacks in the process, as that would be very limiting unless the	 value
       is so big as to provide no value at all with a single thread.

FUTURE DIRECTIONS
       None.

SEE ALSO
       exec, fork(), malloc(), open(), sigaltstack(), sysconf(), ulimit()

       The    Base    Definitions   volume   of	  POSIX.1‐2008,	  <stropts.h>,
       <sys_resource.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
       cal and Electronics Engineers,  Inc  and	 The  Open  Group.   (This  is
       POSIX.1-2008  with  the	2013  Technical Corrigendum 1 applied.) 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.unix.org/online.html .

       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker‐
       nel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group		     2013			 GETRLIMIT(3P)
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