PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

GETRLIMIT(3P)             POSIX Programmer's Manual            GETRLIMIT(3P)

PROLOG         top

       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         top

       getrlimit, setrlimit — control maximum resource consumption

SYNOPSIS         top

       #include <sys/resource.h>

       int getrlimit(int resource, struct rlimit *rlp);
       int setrlimit(int resource, const struct rlimit *rlp);

DESCRIPTION         top

       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         top

       Upon successful completion, getrlimit() and setrlimit() shall return
       0. Otherwise, these functions shall return −1 and set errno to
       indicate the error.

ERRORS         top

       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         top

       None.

APPLICATION USAGE         top

       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         top

       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         top

       None.

SEE ALSO         top

       exec(1p), fork(3p), malloc(3p), open(3p), sigaltstack(3p),
       sysconf(3p), ulimit(3p)

       The Base Definitions volume of POSIX.1‐2008, stropts.h(0p),
       sys_resource.h(0p)

COPYRIGHT         top

       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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                       GETRLIMIT(3P)

Pages that refer to this page: sys_resource.h(0p)exec(3p)fclose(3p)fflush(3p)fputc(3p)fseek(3p)malloc(3p)setrlimit(3p)ulimit(3p)write(3p)limits.conf(5)