# getrlimit

## 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 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 data segment of the
                         process, 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 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 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 total available memory
                         of the process, 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



           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.
    


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