fcntl (nr 72)

Linux Signature

int fcntl(int fd, int cmd, ... /* arg */);

Performs operations on file descriptors. Only fd-level flag operations are supported.

Command	Value	Behaviour
`F_GETFD`	1	Returns the fd flags (currently only `FD_CLOEXEC`)
`F_SETFD`	2	Sets the fd flags to `arg`
`F_GETFL`	3	Returns 0 (no file status flags tracked)
Other	—	Returns `-EINVAL`

Source: osl/src/syscalls/fs.rs — sys_fcntl

Errno	Condition
`-EBADF` (-9)	`fd` is not a valid open fd
`-EINVAL` (-22)	Unknown `cmd`