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 .