WriteFile

Writes bytes to a file or device.

Module: MacOS

Signature

func WriteFile(
    file: *opaque,
    buffer: *const opaque,
    bytesToWrite: uint32,
    bytesWritten: *uint32,
    overlapped: *opaque
) -> bool32;

Parameters

Name	Type	Description
file	*opaque	BSD file descriptor encoded as a pointer.
buffer	*const opaque	Source containing at least bytesToWrite bytes.
bytesToWrite	uint32	Number of bytes requested.
bytesWritten	*uint32	Receives the number of bytes actually written.
overlapped	*opaque	Compatibility parameter; pass null.

Returns

bool32 — nonzero when the underlying write succeeds; zero when it fails.

Description

The operation is synchronous. A successful call may write fewer than bytesToWrite bytes, so callers that require complete output must check bytesWritten and continue from the first unwritten byte.

WARNING

This binding does not expose the underlying macOS error number or retry partial or interrupted writes.

Example

import MacOS::{ GetStdHandle, StdHandle, WriteFile };

let message = c8"hello\n";
var written: uint32 = 0;
let output = GetStdHandle(StdHandle::Output);
let ok = WriteFile(output, message.data, message.length as uint32,
    &written, null);
if ok == 0 || written != message.length as uint32 {
    return 1i32;
}

See also

• Console and I/O — I/O overview
• ReadFile — read bytes