int open(int dir_fd, char *path, int path_len, int flags);
open opens the passed file relative to dir_fd, depending on the
flags passed. It does not create the file if not existent. By default, the file
descriptor will remain open across an exec.
flags can be an OR’d field of the following elements:
O_RDONLY (0b0000001)Makes the file able to be read.
O_WRONLY (0b0000010)Makes the file able to be written to.
O_APPEND (0b0000100)Makes the file be opened at the end of the file, instead of the beginning.
O_CLOEXEC (0b0001000)Will make the file close when exec’d.
O_NOFOLLOW (0b0010000)Do not follow symlinks when opening the file.
O_NONBLOCK (0b0100000)Make the file not block on read or write operations when possible.
O_CLOFORK (0b1000000)Will make the file close when fork’d.
If no O_RDONLY or O_WRONLY is passed, the open operation will
result in a file descriptor supporting only stat and navigating operations.
The syscall returns the opened file descriptor or -1 on error, and errno
is set to the following:
ENOENT: The referenced file does not exist.
EINVAL: Combination of flags is not valid.
EMFILE: Too many files are already owned by the process.
EFAULT: The passed path is outside the available address space.