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fcntl

This module performs file control and I/O control on file
descriptors.  It is an interface to the fcntl() and ioctl() Unix
routines.  File descriptors can be obtained with the fileno() method of
a file or socket object.

Functions

fcntl

fcntl(fd, cmd, arg=0, /)

  Perform the operation `cmd` on file descriptor fd.

  The values used for `cmd` are operating system dependent, and are available
  as constants in the fcntl module, using the same names as used in
  the relevant C header files.  The argument arg is optional, and
  defaults to 0; it may be an int or a string.  If arg is given as a string,
  the return value of fcntl is a string of that length, containing the
  resulting value put in the arg buffer by the operating system.  The length
  of the arg string is not allowed to exceed 1024 bytes.  If the arg given
  is an integer or if none is specified, the result value is an integer
  corresponding to the return value of the fcntl call in the C code.

flock

flock(fd, operation, /)

  Perform the lock operation `operation` on file descriptor `fd`.

  See the Unix manual page for flock(2) for details (On some systems, this
  function is emulated using fcntl()).

ioctl

ioctl(fd, request, arg=0, mutate_flag=True, /)

  Perform the operation `request` on file descriptor `fd`.

  The values used for `request` are operating system dependent, and are available
  as constants in the fcntl or termios library modules, using the same names as
  used in the relevant C header files.

  The argument `arg` is optional, and defaults to 0; it may be an int or a
  buffer containing character data (most likely a string or an array).

  If the argument is a mutable buffer (such as an array) and if the
  mutate_flag argument (which is only allowed in this case) is true then the
  buffer is (in effect) passed to the operating system and changes made by
  the OS will be reflected in the contents of the buffer after the call has
  returned.  The return value is the integer returned by the ioctl system
  call.

  If the argument is a mutable buffer and the mutable_flag argument is false,
  the behavior is as if a string had been passed.

  If the argument is an immutable buffer (most likely a string) then a copy
  of the buffer is passed to the operating system and the return value is a
  string of the same length containing whatever the operating system put in
  the buffer.  The length of the arg buffer in this case is not allowed to
  exceed 1024 bytes.

  If the arg given is an integer or if none is specified, the result value is
  an integer corresponding to the return value of the ioctl call in the C
  code.

lockf

lockf(fd, cmd, len=0, start=0, whence=0, /)

  A wrapper around the fcntl() locking calls.

  `fd` is the file descriptor of the file to lock or unlock, and operation is one
  of the following values:

      LOCK_UN - unlock
      LOCK_SH - acquire a shared lock
      LOCK_EX - acquire an exclusive lock

  When operation is LOCK_SH or LOCK_EX, it can also be bitwise ORed with
  LOCK_NB to avoid blocking on lock acquisition.  If LOCK_NB is used and the
  lock cannot be acquired, an OSError will be raised and the exception will
  have an errno attribute set to EACCES or EAGAIN (depending on the operating
  system -- for portability, check for either value).

  `len` is the number of bytes to lock, with the default meaning to lock to
  EOF.  `start` is the byte offset, relative to `whence`, to that the lock
  starts.  `whence` is as with fileobj.seek(), specifically:

      0 - relative to the start of the file (SEEK_SET)
      1 - relative to the current buffer position (SEEK_CUR)
      2 - relative to the end of the file (SEEK_END)

Other members

DN_ACCESS = 1

DN_ATTRIB = 32

DN_CREATE = 4

DN_DELETE = 8

DN_MODIFY = 2

DN_MULTISHOT = 2147483648

DN_RENAME = 16

FASYNC = 8192

FD_CLOEXEC = 1

F_ADD_SEALS = 1033

F_DUPFD = 0

F_DUPFD_CLOEXEC = 1030

F_EXLCK = 4

F_GETFD = 1

F_GETFL = 3

F_GETLEASE = 1025

F_GETLK = 5

F_GETLK64 = 5

F_GETOWN = 9

F_GETSIG = 11

F_GET_SEALS = 1034

F_NOTIFY = 1026

F_OFD_GETLK = 36

F_OFD_SETLK = 37

F_OFD_SETLKW = 38

F_RDLCK = 0

F_SEAL_GROW = 4

F_SEAL_SEAL = 1

F_SEAL_SHRINK = 2

F_SEAL_WRITE = 8

F_SETFD = 2

F_SETFL = 4

F_SETLEASE = 1024

F_SETLK = 6

F_SETLK64 = 6

F_SETLKW = 7

F_SETLKW64 = 7

F_SETOWN = 8

F_SETSIG = 10

F_SHLCK = 8

F_UNLCK = 2

F_WRLCK = 1

LOCK_EX = 2

LOCK_MAND = 32

LOCK_NB = 4

LOCK_READ = 64

LOCK_RW = 192

LOCK_SH = 1

LOCK_UN = 8

LOCK_WRITE = 128