diff options
Diffstat (limited to 'Doc/library/fcntl.rst')
| -rw-r--r-- | Doc/library/fcntl.rst | 41 |
1 files changed, 26 insertions, 15 deletions
diff --git a/Doc/library/fcntl.rst b/Doc/library/fcntl.rst index 13ad2dd..b93d6ac 100644 --- a/Doc/library/fcntl.rst +++ b/Doc/library/fcntl.rst @@ -13,10 +13,10 @@ ---------------- -This module performs file control and I/O control on file descriptors. It is an -interface to the :c:func:`fcntl` and :c:func:`ioctl` Unix routines. For a -complete description of these calls, see :manpage:`fcntl(2)` and -:manpage:`ioctl(2)` Unix manual pages. +This module performs file and I/O control on file descriptors. It is an +interface to the :c:func:`fcntl` and :c:func:`ioctl` Unix routines. +See the :manpage:`fcntl(2)` and :manpage:`ioctl(2)` Unix manual pages +for full details. .. availability:: Unix, not Emscripten, not WASI. @@ -101,7 +101,7 @@ The module defines the following functions: most likely to result in a segmentation violation or a more subtle data corruption. - If the :c:func:`fcntl` fails, an :exc:`OSError` is raised. + If the :c:func:`fcntl` call fails, an :exc:`OSError` is raised. .. audit-event:: fcntl.fcntl fd,cmd,arg fcntl.fcntl @@ -139,7 +139,7 @@ The module defines the following functions: buffer 1024 bytes long which is then passed to :func:`ioctl` and copied back into the supplied buffer. - If the :c:func:`ioctl` fails, an :exc:`OSError` exception is raised. + If the :c:func:`ioctl` call fails, an :exc:`OSError` exception is raised. An example:: @@ -164,7 +164,7 @@ The module defines the following functions: :manpage:`flock(2)` for details. (On some systems, this function is emulated using :c:func:`fcntl`.) - If the :c:func:`flock` fails, an :exc:`OSError` exception is raised. + If the :c:func:`flock` call fails, an :exc:`OSError` exception is raised. .. audit-event:: fcntl.flock fd,operation fcntl.flock @@ -176,17 +176,28 @@ The module defines the following functions: method are accepted as well) of the file to lock or unlock, and *cmd* is one of the following values: - * :const:`LOCK_UN` -- unlock - * :const:`LOCK_SH` -- acquire a shared lock - * :const:`LOCK_EX` -- acquire an exclusive lock + .. data:: LOCK_UN - When *cmd* is :const:`LOCK_SH` or :const:`LOCK_EX`, it can also be - bitwise ORed with :const:`LOCK_NB` to avoid blocking on lock acquisition. - If :const:`LOCK_NB` is used and the lock cannot be acquired, an + Release an existing lock. + + .. data:: LOCK_SH + + Acquire a shared lock. + + .. data:: LOCK_EX + + Acquire an exclusive lock. + + .. data:: LOCK_NB + + Bitwise OR with any of the other three ``LOCK_*`` constants to make + the request non-blocking. + + If :const:`!LOCK_NB` is used and the lock cannot be acquired, an :exc:`OSError` will be raised and the exception will have an *errno* - attribute set to :const:`EACCES` or :const:`EAGAIN` (depending on the + attribute set to :const:`~errno.EACCES` or :const:`~errno.EAGAIN` (depending on the operating system; for portability, check for both values). On at least some - systems, :const:`LOCK_EX` can only be used if the file descriptor refers to a + systems, :const:`!LOCK_EX` can only be used if the file descriptor refers to a file opened for writing. *len* is the number of bytes to lock, *start* is the byte offset at |