fcntl - manipulate file descriptor

#include <fcntl.h>
int fcntl(int fd, int op, ...);

fcntl() performs one of the operations described below on the open file descriptor fd. The operation is determined by op.

Certain of the operations below are supported only since a particular Linux kernel version. The preferred method of checking whether the host kernel supports a particular operation is to invoke fcntl() with the desired op value and then test whether the call failed with EINVAL, indicating that the kernel does not recognize this value.

Duplicating a file descriptor

F_DUPFD(2const)
F_DUPFD_CLOEXEC(2const)

File descriptor flags

F_GETFD(2const)
F_SETFD(2const)

File status flags

F_GETFL(2const)
F_SETFL(2const)

Advisory record locking

F_SETLK(2const)
F_SETLKW(2const)
F_GETLK(2const)

Open file description locks (non-POSIX)

F_OFD_SETLK(2const)
F_OFD_SETLKW(2const)
F_OFD_GETLK(2const)

Managing signals

F_GETOWN(2const)
F_SETOWN(2const)
F_GETOWN_EX(2const)
F_SETOWN_EX(2const)
F_GETSIG(2const)
F_SETSIG(2const)

Leases

F_SETLEASE(2const)
F_GETLEASE(2const)

Delegations

F_SETDELEG(2const)
F_GETDELEG(2const)

File and directory change notification (dnotify)

F_NOTIFY(2const)

Changing the capacity of a pipe

F_SETPIPE_SZ(2const)
F_GETPIPE_SZ(2const)

File Sealing

F_ADD_SEALS(2const)
F_GET_SEALS(2const)

File read/write hints

F_GET_RW_HINT(2const)
F_SET_RW_HINT(2const)
F_GET_FILE_RW_HINT(2const)
F_SET_FILE_RW_HINT(2const)

For a successful call, the return value depends on the operation.

On error, -1 is returned, and errno is set to indicate the error.

dup2(2), flock(2), open(2), socket(2), lockf(3), capabilities(7), feature_test_macros(7), lslocks(8)