nix 0.27.1

Rust friendly bindings to *nix APIs
Documentation 
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use std::os::unix::io::{AsFd, AsRawFd};
use tempfile::tempfile;

use nix::errno::Errno;
use nix::fcntl;
use nix::pty::openpty;
use nix::sys::termios::{self, tcgetattr, LocalFlags, OutputFlags};
use nix::unistd::{read, write};

/// Helper function analogous to `std::io::Write::write_all`, but for `Fd`s
fn write_all<Fd: AsFd>(f: Fd, buf: &[u8]) {
    let mut len = 0;
    while len < buf.len() {
        len += write(f.as_fd().as_raw_fd(), &buf[len..]).unwrap();
    }
}

// Test tcgetattr on a terminal
#[test]
fn test_tcgetattr_pty() {
    // openpty uses ptname(3) internally
    let _m = crate::PTSNAME_MTX.lock();

    let pty = openpty(None, None).expect("openpty failed");
    termios::tcgetattr(&pty.slave).unwrap();
}

// Test tcgetattr on something that isn't a terminal
#[test]
fn test_tcgetattr_enotty() {
    let file = tempfile().unwrap();
    assert_eq!(termios::tcgetattr(&file).err(), Some(Errno::ENOTTY));
}

// Test modifying output flags
#[test]
fn test_output_flags() {
    // openpty uses ptname(3) internally
    let _m = crate::PTSNAME_MTX.lock();

    // Open one pty to get attributes for the second one
    let mut termios = {
        let pty = openpty(None, None).expect("openpty failed");
        tcgetattr(&pty.slave).expect("tcgetattr failed")
    };

    // Make sure postprocessing '\r' isn't specified by default or this test is useless.
    assert!(!termios
        .output_flags
        .contains(OutputFlags::OPOST | OutputFlags::OCRNL));

    // Specify that '\r' characters should be transformed to '\n'
    // OPOST is specified to enable post-processing
    termios
        .output_flags
        .insert(OutputFlags::OPOST | OutputFlags::OCRNL);

    // Open a pty
    let pty = openpty(None, &termios).unwrap();

    // Write into the master
    let string = "foofoofoo\r";
    write_all(&pty.master, string.as_bytes());

    // Read from the slave verifying that the output has been properly transformed
    let mut buf = [0u8; 10];
    crate::read_exact(&pty.slave, &mut buf);
    let transformed_string = "foofoofoo\n";
    assert_eq!(&buf, transformed_string.as_bytes());
}

// Test modifying local flags
#[test]
fn test_local_flags() {
    // openpty uses ptname(3) internally
    let _m = crate::PTSNAME_MTX.lock();

    // Open one pty to get attributes for the second one
    let mut termios = {
        let pty = openpty(None, None).unwrap();
        tcgetattr(&pty.slave).unwrap()
    };

    // Make sure echo is specified by default or this test is useless.
    assert!(termios.local_flags.contains(LocalFlags::ECHO));

    // Disable local echo
    termios.local_flags.remove(LocalFlags::ECHO);

    // Open a new pty with our modified termios settings
    let pty = openpty(None, &termios).unwrap();

    // Set the master is in nonblocking mode or reading will never return.
    let flags = fcntl::fcntl(pty.master.as_raw_fd(), fcntl::F_GETFL).unwrap();
    let new_flags =
        fcntl::OFlag::from_bits_truncate(flags) | fcntl::OFlag::O_NONBLOCK;
    fcntl::fcntl(pty.master.as_raw_fd(), fcntl::F_SETFL(new_flags)).unwrap();

    // Write into the master
    let string = "foofoofoo\r";
    write_all(&pty.master, string.as_bytes());

    // Try to read from the master, which should not have anything as echoing was disabled.
    let mut buf = [0u8; 10];
    let read = read(pty.master.as_raw_fd(), &mut buf).unwrap_err();
    assert_eq!(read, Errno::EAGAIN);
}