fcntl — The fcntl and ioctl system calls¶
This module performs file and I/O control on file descriptors. It is an
interface to the fcntl() and ioctl() Unix routines.
See the fcntl(2) and ioctl(2) Unix manual pages
for full details.
가용성: Unix, not WASI.
이 모듈의 모든 함수는 첫 번째 인자로 파일 기술자 fd를 받아들입니다. 이것은 sys.stdin.fileno()에 의해 반환된 것과 같은 정수 파일 기술자이거나 sys.stdin 자체와 같은 io.IOBase 객체일 수 있습니다. 이 객체는 실제 파일 기술자를 반환하는 fileno()를 제공합니다.
버전 3.8에서 변경: The fcntl module now contains F_ADD_SEALS, F_GET_SEALS, and
F_SEAL_* constants for sealing of os.memfd_create() file
descriptors.
버전 3.9에서 변경: On macOS, the fcntl module exposes the F_GETPATH constant,
which obtains the path of a file from a file descriptor.
On Linux(>=3.15), the fcntl module exposes the F_OFD_GETLK,
F_OFD_SETLK and F_OFD_SETLKW constants, which are used when working
with open file description locks.
버전 3.10에서 변경: On Linux >= 2.6.11, the fcntl module exposes the F_GETPIPE_SZ and
F_SETPIPE_SZ constants, which allow to check and modify a pipe’s size
respectively.
버전 3.11에서 변경: On FreeBSD, the fcntl module exposes the F_DUP2FD and
F_DUP2FD_CLOEXEC constants, which allow to duplicate a file descriptor,
the latter setting FD_CLOEXEC flag in addition.
버전 3.12에서 변경: On Linux >= 4.5, the fcntl module exposes the FICLONE and
FICLONERANGE constants, which allow to share some data of one file with
another file by reflinking on some filesystems (e.g., btrfs, OCFS2, and
XFS). This behavior is commonly referred to as “copy-on-write”.
버전 3.13에서 변경: On Linux >= 2.6.32, the fcntl module exposes the
F_GETOWN_EX, F_SETOWN_EX, F_OWNER_TID, F_OWNER_PID, F_OWNER_PGRP constants, which allow to direct I/O availability signals
to a specific thread, process, or process group.
On Linux >= 4.13, the fcntl module exposes the
F_GET_RW_HINT, F_SET_RW_HINT, F_GET_FILE_RW_HINT,
F_SET_FILE_RW_HINT, and RWH_WRITE_LIFE_* constants, which allow
to inform the kernel about the relative expected lifetime of writes on
a given inode or via a particular open file description.
On Linux >= 5.1 and NetBSD, the fcntl module exposes the
F_SEAL_FUTURE_WRITE constant for use with F_ADD_SEALS and
F_GET_SEALS operations.
On FreeBSD, the fcntl module exposes the F_READAHEAD, F_ISUNIONSTACK, and F_KINFO constants.
On macOS and FreeBSD, the fcntl module exposes the F_RDAHEAD
constant.
On NetBSD and AIX, the fcntl module exposes the F_CLOSEM
constant.
On NetBSD, the fcntl module exposes the F_MAXFD constant.
On macOS and NetBSD, the fcntl module exposes the F_GETNOSIGPIPE
and F_SETNOSIGPIPE constant.
이 모듈은 다음 함수를 정의합니다:
- fcntl.fcntl(fd, cmd, arg=0, /)¶
Perform the operation cmd on file descriptor fd (file objects providing a
fileno()method are accepted as well). The values used for cmd are operating system dependent, and are available as constants in thefcntlmodule, using the same names as used in the relevant C header files. The argument arg can either be an integer value, abytesobject, or a string. The type and size of arg must match the type and size of the argument of the operation as specified in the relevant C documentation.When arg is an integer, the function returns the integer return value of the C
fcntl()call.When the argument is bytes, it represents a binary structure, for example, created by
struct.pack(). A string value is encoded to binary using the UTF-8 encoding. The binary data is copied to a buffer whose address is passed to the Cfcntl()call. The return value after a successful call is the contents of the buffer, converted to abytesobject. The length of the returned object will be the same as the length of the arg argument. This is limited to 1024 bytes.If the
fcntl()call fails, anOSErroris raised.참고
If the type or the size of arg does not match the type or size of the argument of the operation (for example, if an integer is passed when a pointer is expected, or 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.
인자
fd,cmd,arg로 감사 이벤트fcntl.fcntl을 발생시킵니다.
- fcntl.ioctl(fd, request, arg=0, mutate_flag=True, /)¶
이 함수는 인자 처리가 훨씬 더 복잡하다는 점을 제외하면,
fcntl()함수와 같습니다.The request parameter is limited to values that can fit in 32-bits or 64-bits, depending on the platform. Additional constants of interest for use as the request argument can be found in the
termiosmodule, under the same names as used in the relevant C header files.The parameter arg can be an integer, a bytes-like object, or a string. The type and size of arg must match the type and size of the argument of the operation as specified in the relevant C documentation.
If arg does not support the read-write buffer interface or the mutate_flag is false, behavior is as for the
fcntl()function.If arg supports the read-write buffer interface (like
bytearray) and mutate_flag is true (the default), then the buffer is (in effect) passed to the underlyingioctl()system call, the latter’s return code is passed back to the calling Python, and the buffer’s new contents reflect the action of theioctl(). 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 toioctl()and copied back into the supplied buffer.If the
ioctl()call fails, anOSErrorexception is raised.참고
If the type or size of arg does not match the type or size of the operation’s argument (for example, if an integer is passed when a pointer is expected, or the information returned in the buffer by the operating system is larger than 1024 bytes, or the size of the mutable bytes-like object is too small), this is most likely to result in a segmentation violation or a more subtle data corruption.
예제:
>>> 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])
인자
fd,request,arg로 감사 이벤트fcntl.ioctl을 발생시킵니다.
- fcntl.flock(fd, operation, /)¶
파일 기술자 fd(
fileno()메서드를 제공하는 파일 객체도 허용됩니다)에 대한 잠금 연산 operation을 수행합니다. 자세한 내용은 유닉스 매뉴얼 flock(2)를 참조하십시오. (일부 시스템에서는, 이 함수가fcntl()를 사용하여 에뮬레이트됩니다.)If the
flock()call fails, anOSErrorexception is raised.인자
fd,operation으로 감사 이벤트fcntl.flock을 발생시킵니다.
- fcntl.lockf(fd, cmd, len=0, start=0, whence=0, /)¶
이것은 본질에서
fcntl()잠금 호출에 대한 래퍼입니다. fd는 잠그거나 잠금 해제할 파일의 파일 기술자이고 (fileno()메서드를 제공하는 파일 객체도 허용됩니다), cmd는 다음 값 중 하나입니다:- fcntl.LOCK_UN¶
Release an existing lock.
- fcntl.LOCK_SH¶
Acquire a shared lock.
- fcntl.LOCK_EX¶
Acquire an exclusive lock.
- fcntl.LOCK_NB¶
Bitwise OR with any of the other three
LOCK_*constants to make the request non-blocking.
If
LOCK_NBis used and the lock cannot be acquired, anOSErrorwill be raised and the exception will have an errno attribute set toEACCESorEAGAIN(depending on the operating system; for portability, check for both values). On at least some systems,LOCK_EXcan only be used if the file descriptor refers to a file opened for writing.len은 잠글 바이트 수, start는 whence가 정의하는 기준으로 잠금이 시작되는 바이트 오프셋이며 whence는
io.IOBase.seek()에서와 같은데, 구체적으로 다음과 같습니다:0– relative to the start of the file (os.SEEK_SET)1– relative to the current buffer position (os.SEEK_CUR)2– relative to the end of the file (os.SEEK_END)
start의 기본값은 파일 시작 부분에서 시작한다는 의미인 0입니다. len의 기본값은 파일 끝까지 잠그는 것을 의미하는 0입니다. whence의 기본값도 0입니다.
인자
fd,cmd,len,start,whence로 감사 이벤트fcntl.lockf를 발생시킵니다.
예제 (모두 SVR4 호환 시스템에서):
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)
첫 번째 예제에서 반환 값 변수 rv는 정숫값을 저장합니다; 두 번째 예제에서는 bytes 객체를 저장합니다. lockdata 변수에 대한 구조체 배치는 시스템 종속적입니다 — 그래서 flock() 호출을 사용하는 것이 더 좋을 수 있습니다.