getrlimit(3p) — Linux manual page

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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.1‐2017, stropts.h(0p),
       sys_resource.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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:https://www.opengroup.org/unix/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               2017                     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)