Name	Size	Mode	Actions
2to3.rst.txt	14647	0644	editdlrm
abc.rst.txt	7219	0644	editdlrm
aepack.rst.txt	4257	0644	editdlrm
aetools.rst.txt	3532	0644	editdlrm
aetypes.rst.txt	4257	0644	editdlrm
aifc.rst.txt	7086	0644	editdlrm
al.rst.txt	5309	0644	editdlrm
allos.rst.txt	695	0644	editdlrm
anydbm.rst.txt	4111	0644	editdlrm
archiving.rst.txt	424	0644	editdlrm
argparse.rst.txt	74685	0644	editdlrm
array.rst.txt	10524	0644	editdlrm
ast.rst.txt	10111	0644	editdlrm
asynchat.rst.txt	9206	0644	editdlrm
asyncore.rst.txt	12937	0644	editdlrm
atexit.rst.txt	3910	0644	editdlrm
audioop.rst.txt	10395	0644	editdlrm
autogil.rst.txt	1015	0644	editdlrm
base64.rst.txt	6252	0644	editdlrm
basehttpserver.rst.txt	10404	0644	editdlrm
bastion.rst.txt	2611	0644	editdlrm
bdb.rst.txt	12456	0644	editdlrm
binascii.rst.txt	6508	0644	editdlrm
binhex.rst.txt	1910	0644	editdlrm
bisect.rst.txt	5415	0644	editdlrm
bsddb.rst.txt	7575	0644	editdlrm
bz2.rst.txt	8064	0644	editdlrm
calendar.rst.txt	11282	0644	editdlrm
carbon.rst.txt	15956	0644	editdlrm
cd.rst.txt	11974	0644	editdlrm
cgi.rst.txt	22853	0644	editdlrm
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cgitb.rst.txt	2874	0644	editdlrm
chunk.rst.txt	4955	0644	editdlrm
cmath.rst.txt	7647	0644	editdlrm
cmd.rst.txt	8565	0644	editdlrm
code.rst.txt	7115	0644	editdlrm
codecs.rst.txt	66966	0644	editdlrm
codeop.rst.txt	3774	0644	editdlrm
collections.rst.txt	41448	0644	editdlrm
colorpicker.rst.txt	913	0644	editdlrm
colorsys.rst.txt	1819	0644	editdlrm
commands.rst.txt	2595	0644	editdlrm
compileall.rst.txt	4678	0644	editdlrm
compiler.rst.txt	37464	0644	editdlrm
configparser.rst.txt	19607	0644	editdlrm
constants.rst.txt	2328	0644	editdlrm
contextlib.rst.txt	6012	0644	editdlrm
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cookielib.rst.txt	27875	0644	editdlrm
copy.rst.txt	3351	0644	editdlrm
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crypt.rst.txt	2292	0644	editdlrm
crypto.rst.txt	355	0644	editdlrm
csv.rst.txt	22757	0644	editdlrm
ctypes.rst.txt	90513	0644	editdlrm
curses.ascii.rst.txt	9046	0644	editdlrm
curses.panel.rst.txt	2740	0644	editdlrm
curses.rst.txt	74877	0644	editdlrm
custominterp.rst.txt	570	0644	editdlrm
datatypes.rst.txt	864	0644	editdlrm
datetime.rst.txt	74679	0644	editdlrm
dbhash.rst.txt	3865	0644	editdlrm
dbm.rst.txt	3117	0644	editdlrm
debug.rst.txt	446	0644	editdlrm
decimal.rst.txt	70926	0644	editdlrm
development.rst.txt	640	0644	editdlrm
difflib.rst.txt	30716	0644	editdlrm
dircache.rst.txt	1813	0644	editdlrm
dis.rst.txt	23248	0644	editdlrm
distribution.rst.txt	426	0644	editdlrm
distutils.rst.txt	1958	0644	editdlrm
dl.rst.txt	3392	0644	editdlrm
doctest.rst.txt	73985	0644	editdlrm
docxmlrpcserver.rst.txt	3802	0644	editdlrm
dumbdbm.rst.txt	2841	0644	editdlrm
dummy_thread.rst.txt	1058	0644	editdlrm
dummy_threading.rst.txt	799	0644	editdlrm
easydialogs.rst.txt	10346	0644	editdlrm
email-examples.rst.txt	1271	0644	editdlrm
email.charset.rst.txt	9654	0644	editdlrm
email.encoders.rst.txt	2376	0644	editdlrm
email.errors.rst.txt	4006	0644	editdlrm
email.generator.rst.txt	6132	0644	editdlrm
email.header.rst.txt	7531	0644	editdlrm
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email.mime.rst.txt	9917	0644	editdlrm
email.parser.rst.txt	10327	0644	editdlrm
email.rst.txt	16111	0644	editdlrm
email.utils.rst.txt	6475	0644	editdlrm
ensurepip.rst.txt	5022	0644	editdlrm
errno.rst.txt	6708	0644	editdlrm
exceptions.rst.txt	18343	0644	editdlrm
fcntl.rst.txt	7361	0644	editdlrm
filecmp.rst.txt	5348	0644	editdlrm
fileformats.rst.txt	302	0644	editdlrm
fileinput.rst.txt	7417	0644	editdlrm
filesys.rst.txt	806	0644	editdlrm
fl.rst.txt	17646	0644	editdlrm
fm.rst.txt	2699	0644	editdlrm
fnmatch.rst.txt	3104	0644	editdlrm
formatter.rst.txt	13245	0644	editdlrm
fpectl.rst.txt	4171	0644	editdlrm
fpformat.rst.txt	1747	0644	editdlrm
fractions.rst.txt	5297	0644	editdlrm
framework.rst.txt	11444	0644	editdlrm
frameworks.rst.txt	378	0644	editdlrm
ftplib.rst.txt	15720	0644	editdlrm
functions.rst.txt	75554	0644	editdlrm
functools.rst.txt	7448	0644	editdlrm
future_builtins.rst.txt	2010	0644	editdlrm
gc.rst.txt	9014	0644	editdlrm
gdbm.rst.txt	4882	0644	editdlrm
gensuitemodule.rst.txt	3113	0644	editdlrm
getopt.rst.txt	6670	0644	editdlrm
getpass.rst.txt	1876	0644	editdlrm
gettext.rst.txt	29040	0644	editdlrm
gl.rst.txt	6009	0644	editdlrm
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grp.rst.txt	2256	0644	editdlrm
gzip.rst.txt	4828	0644	editdlrm
hashlib.rst.txt	7379	0644	editdlrm
heapq.rst.txt	13185	0644	editdlrm
hmac.rst.txt	3073	0644	editdlrm
hotshot.rst.txt	4289	0644	editdlrm
htmllib.rst.txt	7379	0644	editdlrm
htmlparser.rst.txt	11640	0644	editdlrm
httplib.rst.txt	37454	0644	editdlrm
i18n.rst.txt	409	0644	editdlrm
ic.rst.txt	5005	0644	editdlrm
idle.rst.txt	22182	0644	editdlrm
imageop.rst.txt	4001	0644	editdlrm
imaplib.rst.txt	17221	0644	editdlrm
imgfile.rst.txt	2765	0644	editdlrm
imghdr.rst.txt	2635	0644	editdlrm
imp.rst.txt	12593	0644	editdlrm
importlib.rst.txt	1126	0644	editdlrm
imputil.rst.txt	7023	0644	editdlrm
index.rst.txt	2287	0644	editdlrm
inspect.rst.txt	28151	0644	editdlrm
internet.rst.txt	950	0644	editdlrm
intro.rst.txt	2803	0644	editdlrm
io.rst.txt	39015	0644	editdlrm
ipc.rst.txt	630	0644	editdlrm
itertools.rst.txt	36324	0644	editdlrm
jpeg.rst.txt	3858	0644	editdlrm
json.rst.txt	25545	0644	editdlrm
keyword.rst.txt	617	0644	editdlrm
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linecache.rst.txt	1887	0644	editdlrm
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logging.config.rst.txt	31560	0644	editdlrm
logging.handlers.rst.txt	28153	0644	editdlrm
logging.rst.txt	46882	0644	editdlrm
mac.rst.txt	791	0644	editdlrm
macos.rst.txt	3824	0644	editdlrm
macosa.rst.txt	3964	0644	editdlrm
macostools.rst.txt	4017	0644	editdlrm
macpath.rst.txt	650	0644	editdlrm
mailbox.rst.txt	68129	0644	editdlrm
mailcap.rst.txt	3675	0644	editdlrm
markup.rst.txt	1249	0644	editdlrm
marshal.rst.txt	5689	0644	editdlrm
math.rst.txt	10920	0644	editdlrm
md5.rst.txt	2815	0644	editdlrm
mhlib.rst.txt	3966	0644	editdlrm
mimetools.rst.txt	4504	0644	editdlrm
mimetypes.rst.txt	9839	0644	editdlrm
mimewriter.rst.txt	3360	0644	editdlrm
mimify.rst.txt	3519	0644	editdlrm
miniaeframe.rst.txt	2564	0644	editdlrm
misc.rst.txt	248	0644	editdlrm
mm.rst.txt	447	0644	editdlrm
mmap.rst.txt	10481	0644	editdlrm
modulefinder.rst.txt	3380	0644	editdlrm
modules.rst.txt	382	0644	editdlrm
msilib.rst.txt	19062	0644	editdlrm
msvcrt.rst.txt	4346	0644	editdlrm
multifile.rst.txt	6613	0644	editdlrm
multiprocessing.rst.txt	92621	0644	editdlrm
mutex.rst.txt	1939	0644	editdlrm
netdata.rst.txt	432	0644	editdlrm
netrc.rst.txt	3119	0644	editdlrm
new.rst.txt	2653	0644	editdlrm
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nntplib.rst.txt	14531	0644	editdlrm
numbers.rst.txt	8007	0644	editdlrm
numeric.rst.txt	751	0644	editdlrm
operator.rst.txt	22092	0644	editdlrm
optparse.rst.txt	77101	0644	editdlrm
os.path.rst.txt	13094	0644	editdlrm
os.rst.txt	82580	0644	editdlrm
ossaudiodev.rst.txt	17309	0644	editdlrm
othergui.rst.txt	2721	0644	editdlrm
parser.rst.txt	15385	0644	editdlrm
pdb.rst.txt	16043	0644	editdlrm
persistence.rst.txt	826	0644	editdlrm
pickle.rst.txt	37262	0644	editdlrm
pickletools.rst.txt	1997	0644	editdlrm
pipes.rst.txt	3786	0644	editdlrm
pkgutil.rst.txt	7714	0644	editdlrm
platform.rst.txt	9554	0644	editdlrm
plistlib.rst.txt	4134	0644	editdlrm
popen2.rst.txt	7022	0644	editdlrm
poplib.rst.txt	6220	0644	editdlrm
posix.rst.txt	3630	0644	editdlrm
posixfile.rst.txt	7200	0644	editdlrm
pprint.rst.txt	9071	0644	editdlrm
profile.rst.txt	28666	0644	editdlrm
pty.rst.txt	1762	0644	editdlrm
pwd.rst.txt	2725	0644	editdlrm
pyclbr.rst.txt	3296	0644	editdlrm
pydoc.rst.txt	4083	0644	editdlrm
pyexpat.rst.txt	28891	0644	editdlrm
python.rst.txt	514	0644	editdlrm
py_compile.rst.txt	2479	0644	editdlrm
queue.rst.txt	7034	0644	editdlrm
quopri.rst.txt	2670	0644	editdlrm
random.rst.txt	13319	0644	editdlrm
re.rst.txt	55102	0644	editdlrm
readline.rst.txt	10513	0644	editdlrm
repr.rst.txt	4718	0644	editdlrm
resource.rst.txt	9595	0644	editdlrm
restricted.rst.txt	3327	0644	editdlrm
rexec.rst.txt	11742	0644	editdlrm
rfc822.rst.txt	14037	0644	editdlrm
rlcompleter.rst.txt	2494	0644	editdlrm
robotparser.rst.txt	2190	0644	editdlrm
runpy.rst.txt	6938	0644	editdlrm
sched.rst.txt	4644	0644	editdlrm
scrolledtext.rst.txt	1379	0644	editdlrm
select.rst.txt	20705	0644	editdlrm
sets.rst.txt	14973	0644	editdlrm
sgi.rst.txt	322	0644	editdlrm
sgmllib.rst.txt	10664	0644	editdlrm
sha.rst.txt	2807	0644	editdlrm
shelve.rst.txt	8319	0644	editdlrm
shlex.rst.txt	11313	0644	editdlrm
shutil.rst.txt	13491	0644	editdlrm
signal.rst.txt	10719	0644	editdlrm
simplehttpserver.rst.txt	4559	0644	editdlrm
simplexmlrpcserver.rst.txt	10881	0644	editdlrm
site.rst.txt	7880	0644	editdlrm
smtpd.rst.txt	2464	0644	editdlrm
smtplib.rst.txt	14906	0644	editdlrm
sndhdr.rst.txt	1759	0644	editdlrm
socket.rst.txt	40765	0644	editdlrm
socketserver.rst.txt	22512	0644	editdlrm
someos.rst.txt	599	0644	editdlrm
spwd.rst.txt	2825	0644	editdlrm
sqlite3.rst.txt	35448	0644	editdlrm
ssl.rst.txt	76554	0644	editdlrm
stat.rst.txt	7778	0644	editdlrm
statvfs.rst.txt	1300	0644	editdlrm
stdtypes.rst.txt	122668	0644	editdlrm
string.rst.txt	44085	0644	editdlrm
stringio.rst.txt	4166	0644	editdlrm
stringprep.rst.txt	4238	0644	editdlrm
strings.rst.txt	746	0644	editdlrm
struct.rst.txt	17100	0644	editdlrm
subprocess.rst.txt	33648	0644	editdlrm
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telnetlib.rst.txt	7482	0644	editdlrm
tempfile.rst.txt	10504	0644	editdlrm
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__main__.rst.txt	535	0644	editdlrm

:mod:`fcntl` --- The ``fcntl`` and ``ioctl`` system calls ========================================================= .. module:: fcntl :platform: Unix :synopsis: The fcntl() and ioctl() system calls. .. sectionauthor:: Jaap Vermeulen .. index:: pair: UNIX; file control pair: UNIX; I/O control 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. All functions in this module take a file descriptor *fd* as their first argument. This can be an integer file descriptor, such as returned by ``sys.stdin.fileno()``, or a file object, such as ``sys.stdin`` itself, which provides a :meth:`~io.IOBase.fileno` which returns a genuine file descriptor. The module defines the following functions: .. function:: fcntl(fd, op[, arg]) Perform the operation *op* on file descriptor *fd* (file objects providing a :meth:`~io.IOBase.fileno` method are accepted as well). The values used for for *op* are operating system dependent, and are available as constants in the :mod:`fcntl` module, using the same names as used in the relevant C header files. The argument *arg* is optional, and defaults to the integer value ``0``. When present, it can either be an integer value, or a string. With the argument missing or an integer value, the return value of this function is the integer return value of the C :c:func:`fcntl` call. When the argument is a string it represents a binary structure, e.g. created by :func:`struct.pack`. The binary data is copied to a buffer whose address is passed to the C :c:func:`fcntl` call. The return value after a successful call is the contents of the buffer, converted to a string object. The length of the returned string will be the same as the length of the *arg* argument. This is limited to 1024 bytes. If the information returned in the buffer by the operating system is larger than 1024 bytes, this is most likely to result in a segmentation violation or a more subtle data corruption. If the :c:func:`fcntl` fails, an :exc:`IOError` is raised. .. function:: ioctl(fd, op[, arg[, mutate_flag]]) This function is identical to the :func:`~fcntl.fcntl` function, except that the operations are typically defined in the library module :mod:`termios` and the argument handling is even more complicated. The op parameter is limited to values that can fit in 32-bits. Additional constants of interest for use as the *op* argument can be found in the :mod:`termios` module, under the same names as used in the relevant C header files. The parameter *arg* can be one of an integer, absent (treated identically to the integer ``0``), an object supporting the read-only buffer interface (most likely a plain Python string) or an object supporting the read-write buffer interface. In all but the last case, behaviour is as for the :func:`~fcntl.fcntl` function. If a mutable buffer is passed, then the behaviour is determined by the value of the *mutate_flag* parameter. If it is false, the buffer's mutability is ignored and behaviour is as for a read-only buffer, except that the 1024 byte limit mentioned above is avoided -- so long as the buffer you pass is as least as long as what the operating system wants to put there, things should work. If *mutate_flag* is true, then the buffer is (in effect) passed to the underlying :func:`ioctl` system call, the latter's return code is passed back to the calling Python, and the buffer's new contents reflect the action of the :func:`ioctl`. This is a slight simplification, because if the supplied buffer is less than 1024 bytes long it is first copied into a static buffer 1024 bytes long which is then passed to :func:`ioctl` and copied back into the supplied buffer. If *mutate_flag* is not supplied, then from Python 2.5 it defaults to true, which is a change from versions 2.3 and 2.4. Supply the argument explicitly if version portability is a priority. If the :c:func:`ioctl` fails, an :exc:`IOError` exception is raised. An example:: >>> import array, fcntl, struct, termios, os >>> os.getpgrp() 13341 >>> struct.unpack('h', fcntl.ioctl(0, termios.TIOCGPGRP, " "))[0] 13341 >>> buf = array.array('h', [0]) >>> fcntl.ioctl(0, termios.TIOCGPGRP, buf, 1) 0 >>> buf array('h', [13341]) .. function:: flock(fd, op) Perform the lock operation *op* on file descriptor *fd* (file objects providing a :meth:`~io.IOBase.fileno` method are accepted as well). See the Unix manual :manpage:`flock(2)` for details. (On some systems, this function is emulated using :c:func:`fcntl`.) If the :c:func:`flock` fails, an :exc:`IOError` exception is raised. .. function:: lockf(fd, operation, [length, [start, [whence]]]) This is essentially a wrapper around the :func:`~fcntl.fcntl` locking calls. *fd* is the file descriptor of the file to lock or unlock, and *operation* is one of the following values: * :const:`LOCK_UN` -- unlock * :const:`LOCK_SH` -- acquire a shared lock * :const:`LOCK_EX` -- acquire an exclusive lock When *operation* 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 :exc:`IOError` will be raised and the exception will have an *errno* attribute set to :const:`EACCES` or :const:`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 file opened for writing. *length* is the number of bytes to lock, *start* is the byte offset at which the lock starts, relative to *whence*, and *whence* is as with :func:`io.IOBase.seek`, specifically: * :const:`0` -- relative to the start of the file (:data:`os.SEEK_SET`) * :const:`1` -- relative to the current buffer position (:data:`os.SEEK_CUR`) * :const:`2` -- relative to the end of the file (:data:`os.SEEK_END`) The default for *start* is 0, which means to start at the beginning of the file. The default for *length* is 0 which means to lock to the end of the file. The default for *whence* is also 0. Examples (all on a SVR4 compliant system):: import struct, fcntl, os f = open(...) rv = fcntl.fcntl(f, fcntl.F_SETFL, os.O_NDELAY) lockdata = struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 0, 0, 0) rv = fcntl.fcntl(f, fcntl.F_SETLKW, lockdata) Note that in the first example the return value variable *rv* will hold an integer value; in the second example it will hold a string value. The structure lay-out for the *lockdata* variable is system dependent --- therefore using the :func:`flock` call may be better. .. seealso:: Module :mod:`os` If the locking flags :data:`~os.O_SHLOCK` and :data:`~os.O_EXLOCK` are present in the :mod:`os` module (on BSD only), the :func:`os.open` function provides an alternative to the :func:`lockf` and :func:`flock` functions.