Module: sys.fd

Source: ./sys/fd.reef

Overview

sys/fd - File descriptor operations

Low-level file descriptor API for pipes, dup, open/close, and fcntl. For higher-level file I/O, use the io module instead.

Example - Pipe: let fds = fd_pipe() fd_write(fds[1], "hello") let msg = fd_read(fds[0], 32) fd_close(fds[0]) fd_close(fds[1])

Example - Open file: let fd = fd_open("/tmp/test.txt", O_WRONLY() | O_CREAT() | O_TRUNC(), 0o644) fd_write(fd, "hello world") fd_close(fd)

Functions

fn fd_open(path: string, flags: int, mode: int): int

Open a file descriptor

fn fd_close(fd: int): int

Close a file descriptor

fn fd_read(fd: int, max_len: int): string

Read from a file descriptor, returns data as string

fn fd_write(fd: int, data: string): int

Write string data to a file descriptor

fn fd_dup(oldfd: int): int

Duplicate a file descriptor

fn fd_dup2(oldfd: int, newfd: int): int

Duplicate fd to specific number

fn fd_pipe(): option.Option[[int]]

Create a pipe, returns [read_fd, write_fd] 0.9.2 C16: Some([read, write]) or None. This returned an EMPTY ARRAY as its failure signal, and callers indexed [0]/[1] straight away -- reproduced under fd exhaustion as array index 1 out of bounds (length 0).

DELIBERATELY NO fd_pipe_or. None means the pipe(2) call FAILED (EMFILE, ENFILE); it is not a missing lookup. Handing back a caller-supplied array would give out file descriptors that were never opened, and the caller would read and write them. Failures are handled, not defaulted.

fn fd_set_nonblocking(fd: int, enable: bool): int

Set non-blocking mode on fd

fn fd_set_cloexec(fd: int, enable: bool): int

Set close-on-exec flag on fd

fn STDIN(): int

Standard file descriptor constants

fn STDOUT(): int

fn STDERR(): int

fn O_RDONLY(): int

Open flag constants

fn O_WRONLY(): int

fn O_RDWR(): int

fn O_CREAT(): int

fn O_TRUNC(): int

fn O_APPEND(): int

fn O_CLOEXEC(): int

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