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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 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  cre-
              ated  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 num-
              ber 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  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
       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(3P)