F_GETFL, F_SETFL

Standard C library (libc, -lc)

#include <fcntl.h>

int fcntl(int fd, F_GETFL);
int fcntl(int fd, F_SETFL, int arg);

Each open file description has certain associated status flags, initialized by open(2) and possibly modified by fcntl(2). Duplicated file descriptors (made with dup(2), F_DUPFD(2const), fork(2), etc.) refer to the same open file description, and thus share the same file status flags.

The file status flags and their semantics are described in open(2).

F_GETFL

Return (as the function result) the file access mode and the file status flags; arg is ignored.

F_SETFL

Set the file status flags to the value specified by arg. File access mode (O_RDONLY, O_WRONLY, O_RDWR) and file creation flags (i.e., O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC) in arg are ignored. On Linux, this operation can change only the O_APPEND, O_ASYNC, O_DIRECT, O_NOATIME, and O_NONBLOCK flags. It is not possible to change the O_DSYNC and O_SYNC flags; see BUGS, below.

F_GETFL

Value of file status flags.

F_SETFL

Zero.

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

See fcntl(2).

EPERM

Attempted to clear the O_APPEND flag on a file that has the append-only attribute set.

POSIX.1-2024.

SVr4, 4.3BSD, POSIX.1-1988.

fcntl(2), open(2)