trusty (3) getrlimit.3posix.gz

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 .