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lockf(3)                Library Functions Manual                lockf(3)

ИМЯ

       lockf - apply, test or remove a POSIX lock on an open file

БИБЛИОТЕКА

       Standard C library (libc, -lc)

СИНТАКСИС

       #include <unistd.h>

       int lockf(int fd, int op, off_t len);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       lockf():
           _XOPEN_SOURCE >= 500
               || /* glibc >= 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

ОПИСАНИЕ

       Apply, test, or remove a POSIX lock on a section of an open file.
       The file is specified by fd, a file descriptor open for writing,
       the action by op, and the section consists of byte positions
       pos..pos+len-1 if len is positive, and pos-len..pos-1 if len is
       negative, where pos is the current file position, and if len is
       zero, the section extends from the current file position to
       infinity, encompassing the present and future end-of-file
       positions.  In all cases, the section may extend past current
       end-of-file.

       On Linux, lockf() is just an interface on top of fcntl(2)
       locking.  Many other systems implement lockf() in this way, but
       note that POSIX.1 leaves the relationship between lockf() and
       fcntl(2) locks unspecified.  A portable application should
       probably avoid mixing calls to these interfaces.

       Valid operations are given below:

       F_LOCK Set an exclusive lock on the specified section of the
              file.  If (part of) this section is already locked, the
              call blocks until the previous lock is released.  If this
              section overlaps an earlier locked section, both are
              merged.  File locks are released as soon as the process
              holding the locks closes some file descriptor for the
              file.  A child process does not inherit these locks.

       F_TLOCK
              Same as F_LOCK but the call never blocks and returns an
              error instead if the file is already locked.

       F_ULOCK
              Unlock the indicated section of the file.  This may cause
              a locked section to be split into two locked sections.

       F_TEST Test the lock: return 0 if the specified section is
              unlocked or locked by this process; return -1, set errno
              to EAGAIN (EACCES on some other systems), if another
              process holds a lock.

ЗНАЧЕНИЕ, ВОЗВРАЩАЕМОЕ ФУНКЦИЕЙ

       On success, zero is returned.  On error, -1 is returned, and
       errno is set to indicate the error.

ОШИБКИ

       EACCES or EAGAIN
              The file is locked and F_TLOCK or F_TEST was specified, or
              the operation is prohibited because the file has been
              memory-mapped by another process.

       EBADF  fd is not an open file descriptor; or op is F_LOCK or
              F_TLOCK and fd is not a writable file descriptor.

       EDEADLK
              op was F_LOCK and this lock operation would cause a
              deadlock.

       EINTR  While waiting to acquire a lock, the call was interrupted
              by delivery of a signal caught by a handler; see
              signal(7).

       EINVAL An invalid operation was specified in op.

       ENOLCK Too many segment locks open, lock table is full.

АТРИБУТЫ

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           │ Attribute     │ Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ lockf()                             │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

СТАНДАРТЫ

       POSIX.1-2008.

ИСТОРИЯ

       POSIX.1-2001, SVr4.

СМОТРИТЕ ТАКЖЕ

       fcntl(2), flock(2)

       locks.txt and mandatory-locking.txt in the Linux kernel source
       directory Documentation/filesystems (on older kernels, these
       files are directly under the Documentation directory, and
       mandatory-locking.txt is called mandatory.txt)

КОЛОФОН

       This page is part of the man-pages (Linux kernel and C library
       user-space interface documentation) project.  Information about
       the project can be found at 
       ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report
       for this manual page, see
       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
       This page was obtained from the tarball man-pages-6.9.1.tar.gz
       fetched from
       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
       2024-06-26.  If you discover any rendering problems in this HTML
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       part of the original manual page), send a mail to
       man-pages@man7.org

Linux man-pages 6.9.1          2024-05-02                       lockf(3)

Страницы, которые ссылаются на эту страницу: fcntl(2), flock(2), flockfile(3), off_t(3type), lslocks(8)