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Diffstat (limited to 'Help/command/file.rst')
-rw-r--r-- | Help/command/file.rst | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/Help/command/file.rst b/Help/command/file.rst index dbc4149..600464e 100644 --- a/Help/command/file.rst +++ b/Help/command/file.rst @@ -305,3 +305,33 @@ status messages (subject to the :variable:`CMAKE_INSTALL_MESSAGE` variable), and ``NO_SOURCE_PERMISSIONS`` is default. Installation scripts generated by the :command:`install` command use this signature (with some undocumented options for internal use). + +------------------------------------------------------------------------------ + +:: + + file(LOCK <path> [DIRECTORY] [RELEASE] + [GUARD <FUNCTION|FILE|PROCESS>] + [RESULT_VARIABLE <variable>] + [TIMEOUT <seconds>]) + +Lock a file specified by ``<path>`` if no ``DIRECTORY`` option present and file +``<path>/cmake.lock`` otherwise. File will be locked for scope defined by +``GUARD`` option (default value is ``PROCESS``). ``RELEASE`` option can be used +to unlock file explicitly. If option ``TIMEOUT`` is not specified CMake will +wait until lock succeed or until fatal error occurs. If ``TIMEOUT`` is set to +``0`` lock will be tried once and result will be reported immediately. If +``TIMEOUT`` is not ``0`` CMake will try to lock file for the period specified +by ``<seconds>`` value. Any errors will be interpreted as fatal if there is no +``RESULT_VARIABLE`` option. Otherwise result will be stored in ``<variable>`` +and will be ``0`` on success or error message on failure. + +Note that lock is advisory - there is no guarantee that other processes will +respect this lock, i.e. lock synchronize two or more CMake instances sharing +some modifiable resources. Similar logic applied to ``DIRECTORY`` option - +locking parent directory doesn't prevent other ``LOCK`` commands to lock any +child directory or file. + +Trying to lock file twice is not allowed. Any intermediate directories and +file itself will be created if they not exist. ``GUARD`` and ``TIMEOUT`` +options ignored on ``RELEASE`` operation. |