PosixUnistd

<

pub fn<.C> write(
    FileDescriptor: i32,
    [abi.NoCapture] Buffer: readonly byte*,
    Count: usize
) -> isize;

Performs one raw POSIX descriptor write.

This declaration exposes host write directly. It may block, mutate the descriptor offset and external state, return a positive short count, and set thread-local errno on failure. A closed pipe or socket may deliver SIGPIPE before a negative result becomes observable; canonical std.io uses the scoped internal platform helper instead.

FileDescriptor: Any target POSIX descriptor value. Invalid or unsuitable values produce an ordinary negative failure result. Buffer: Borrowed first byte of the range to read. Count: Maximum number of bytes to read from Buffer. Return: A count from zero through Count, or a negative failure value. Pre: Safety: when Count is positive, Buffer is nonnull and has valid provenance for a live byte-aligned readable range of at least Count bytes; when Count is zero, the pointer may be null and is not accessed. Pre: Safety: the complete range remains live and free of conflicting concurrent mutation until return and is neither written nor retained. Pre: Safety: the target uses the declared int/size_t/ssize_t C ABI, descriptor runtime state is available, and no foreign unwind crosses into Sn. Warning: Performs no retry, grants no atomic-write guarantee, and may terminate through the host SIGPIPE disposition.

Example

module example.write;
from std.posix.unistd import write;
fn Main() -> i32 {
    unsafe {
        let Written: isize = write(1, c"x", 1);
        if Written < 0 {
            return 1;
        }
    }
    return 0;
}