400 lines
11 KiB
Rust
400 lines
11 KiB
Rust
//! TTY related functionality.
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use std::ffi::CStr;
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use std::fs::File;
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use std::io::{Error, ErrorKind, Result};
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use std::mem::MaybeUninit;
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use std::os::unix::io::{AsRawFd, FromRawFd, RawFd};
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use std::os::unix::process::CommandExt;
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use std::process::{Child, Command, Stdio};
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use std::{env, ptr};
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use libc::{self, c_int, winsize, TIOCSCTTY};
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use log::error;
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use mio::unix::EventedFd;
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use nix::pty::openpty;
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#[cfg(any(target_os = "linux", target_os = "macos"))]
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use nix::sys::termios::{self, InputFlags, SetArg};
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use signal_hook::consts as sigconsts;
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use signal_hook_mio::v0_6::Signals;
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use crate::config::PtyConfig;
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use crate::event::{OnResize, WindowSize};
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use crate::tty::{ChildEvent, EventedPty, EventedReadWrite};
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macro_rules! die {
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($($arg:tt)*) => {{
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error!($($arg)*);
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std::process::exit(1);
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}}
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}
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/// Get raw fds for master/slave ends of a new PTY.
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fn make_pty(size: winsize) -> Result<(RawFd, RawFd)> {
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let mut window_size = size;
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window_size.ws_xpixel = 0;
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window_size.ws_ypixel = 0;
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let ends = openpty(Some(&window_size), None)?;
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Ok((ends.master, ends.slave))
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}
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/// Really only needed on BSD, but should be fine elsewhere.
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fn set_controlling_terminal(fd: c_int) {
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let res = unsafe {
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// TIOSCTTY changes based on platform and the `ioctl` call is different
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// based on architecture (32/64). So a generic cast is used to make sure
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// there are no issues. To allow such a generic cast the clippy warning
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// is disabled.
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#[allow(clippy::cast_lossless)]
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libc::ioctl(fd, TIOCSCTTY as _, 0)
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};
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if res < 0 {
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die!("ioctl TIOCSCTTY failed: {}", Error::last_os_error());
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}
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}
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#[derive(Debug)]
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struct Passwd<'a> {
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name: &'a str,
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dir: &'a str,
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shell: &'a str,
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}
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/// Return a Passwd struct with pointers into the provided buf.
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///
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/// # Unsafety
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///
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/// If `buf` is changed while `Passwd` is alive, bad thing will almost certainly happen.
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fn get_pw_entry(buf: &mut [i8; 1024]) -> Result<Passwd<'_>> {
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// Create zeroed passwd struct.
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let mut entry: MaybeUninit<libc::passwd> = MaybeUninit::uninit();
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let mut res: *mut libc::passwd = ptr::null_mut();
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// Try and read the pw file.
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let uid = unsafe { libc::getuid() };
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let status = unsafe {
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libc::getpwuid_r(uid, entry.as_mut_ptr(), buf.as_mut_ptr() as *mut _, buf.len(), &mut res)
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};
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let entry = unsafe { entry.assume_init() };
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if status < 0 {
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return Err(Error::new(ErrorKind::Other, "getpwuid_r failed"));
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}
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if res.is_null() {
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return Err(Error::new(ErrorKind::Other, "pw not found"));
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}
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// Sanity check.
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assert_eq!(entry.pw_uid, uid);
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// Build a borrowed Passwd struct.
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Ok(Passwd {
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name: unsafe { CStr::from_ptr(entry.pw_name).to_str().unwrap() },
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dir: unsafe { CStr::from_ptr(entry.pw_dir).to_str().unwrap() },
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shell: unsafe { CStr::from_ptr(entry.pw_shell).to_str().unwrap() },
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})
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}
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pub struct Pty {
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child: Child,
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file: File,
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token: mio::Token,
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signals: Signals,
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signals_token: mio::Token,
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}
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impl Pty {
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pub fn child(&self) -> &Child {
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&self.child
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}
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pub fn file(&self) -> &File {
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&self.file
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}
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}
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/// Look for a shell in the `$SHELL` environment variable, then in `passwd`.
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fn default_shell(pw: &Passwd<'_>) -> String {
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env::var("SHELL").unwrap_or_else(|_| pw.shell.to_owned())
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}
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#[cfg(not(target_os = "macos"))]
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fn default_shell_command(pw: &Passwd<'_>) -> Command {
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Command::new(default_shell(pw))
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}
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#[cfg(target_os = "macos")]
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fn default_shell_command(pw: &Passwd<'_>) -> Command {
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let shell = default_shell(pw);
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let shell_name = shell.rsplit('/').next().unwrap();
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// On macOS, use the `login` command so the shell will appear as a tty session.
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let mut login_command = Command::new("/usr/bin/login");
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// Exec the shell with argv[0] prepended by '-' so it becomes a login shell.
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// `login` normally does this itself, but `-l` disables this.
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let exec = format!("exec -a -{} {}", shell_name, shell);
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// -f: Bypasses authentication for the already-logged-in user.
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// -l: Skips changing directory to $HOME and prepending '-' to argv[0].
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// -p: Preserves the environment.
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login_command.args(["-flp", pw.name, "/bin/sh", "-c", &exec]);
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login_command
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}
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/// Create a new TTY and return a handle to interact with it.
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pub fn new(config: &PtyConfig, window_size: WindowSize, window_id: u64) -> Result<Pty> {
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let (master, slave) = make_pty(window_size.to_winsize())?;
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#[cfg(any(target_os = "linux", target_os = "macos"))]
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if let Ok(mut termios) = termios::tcgetattr(master) {
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// Set character encoding to UTF-8.
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termios.input_flags.set(InputFlags::IUTF8, true);
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let _ = termios::tcsetattr(master, SetArg::TCSANOW, &termios);
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}
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let mut buf = [0; 1024];
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let pw = get_pw_entry(&mut buf)?;
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let mut builder = if let Some(shell) = config.shell.as_ref() {
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let mut cmd = Command::new(shell.program());
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cmd.args(shell.args());
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cmd
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} else {
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default_shell_command(&pw)
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};
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// Setup child stdin/stdout/stderr as slave fd of PTY.
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// Ownership of fd is transferred to the Stdio structs and will be closed by them at the end of
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// this scope. (It is not an issue that the fd is closed three times since File::drop ignores
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// error on libc::close.).
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builder.stdin(unsafe { Stdio::from_raw_fd(slave) });
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builder.stderr(unsafe { Stdio::from_raw_fd(slave) });
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builder.stdout(unsafe { Stdio::from_raw_fd(slave) });
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// Setup shell environment.
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let window_id = window_id.to_string();
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builder.env("ALACRITTY_WINDOW_ID", &window_id);
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builder.env("LOGNAME", pw.name);
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builder.env("USER", pw.name);
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builder.env("HOME", pw.dir);
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// Set Window ID for clients relying on X11 hacks.
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builder.env("WINDOWID", window_id);
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unsafe {
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builder.pre_exec(move || {
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// Create a new process group.
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let err = libc::setsid();
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if err == -1 {
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return Err(Error::new(ErrorKind::Other, "Failed to set session id"));
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}
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set_controlling_terminal(slave);
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// No longer need slave/master fds.
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libc::close(slave);
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libc::close(master);
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libc::signal(libc::SIGCHLD, libc::SIG_DFL);
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libc::signal(libc::SIGHUP, libc::SIG_DFL);
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libc::signal(libc::SIGINT, libc::SIG_DFL);
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libc::signal(libc::SIGQUIT, libc::SIG_DFL);
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libc::signal(libc::SIGTERM, libc::SIG_DFL);
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libc::signal(libc::SIGALRM, libc::SIG_DFL);
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Ok(())
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});
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}
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// Handle set working directory option.
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if let Some(dir) = &config.working_directory {
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builder.current_dir(dir);
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}
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// Prepare signal handling before spawning child.
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let signals = Signals::new([sigconsts::SIGCHLD]).expect("error preparing signal handling");
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match builder.spawn() {
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Ok(child) => {
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unsafe {
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// Maybe this should be done outside of this function so nonblocking
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// isn't forced upon consumers. Although maybe it should be?
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set_nonblocking(master);
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}
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let mut pty = Pty {
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child,
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file: unsafe { File::from_raw_fd(master) },
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token: mio::Token::from(0),
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signals,
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signals_token: mio::Token::from(0),
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};
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pty.on_resize(window_size);
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Ok(pty)
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},
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Err(err) => Err(Error::new(
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err.kind(),
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format!(
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"Failed to spawn command '{}': {}",
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builder.get_program().to_string_lossy(),
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err
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),
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)),
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}
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}
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impl Drop for Pty {
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fn drop(&mut self) {
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// Make sure the PTY is terminated properly.
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unsafe {
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libc::kill(self.child.id() as i32, libc::SIGHUP);
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}
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let _ = self.child.wait();
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}
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}
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impl EventedReadWrite for Pty {
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type Reader = File;
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type Writer = File;
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#[inline]
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fn register(
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&mut self,
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poll: &mio::Poll,
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token: &mut dyn Iterator<Item = mio::Token>,
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interest: mio::Ready,
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poll_opts: mio::PollOpt,
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) -> Result<()> {
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self.token = token.next().unwrap();
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poll.register(&EventedFd(&self.file.as_raw_fd()), self.token, interest, poll_opts)?;
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self.signals_token = token.next().unwrap();
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poll.register(
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&self.signals,
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self.signals_token,
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mio::Ready::readable(),
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mio::PollOpt::level(),
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)
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}
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#[inline]
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fn reregister(
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&mut self,
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poll: &mio::Poll,
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interest: mio::Ready,
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poll_opts: mio::PollOpt,
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) -> Result<()> {
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poll.reregister(&EventedFd(&self.file.as_raw_fd()), self.token, interest, poll_opts)?;
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poll.reregister(
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&self.signals,
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self.signals_token,
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mio::Ready::readable(),
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mio::PollOpt::level(),
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)
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}
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#[inline]
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fn deregister(&mut self, poll: &mio::Poll) -> Result<()> {
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poll.deregister(&EventedFd(&self.file.as_raw_fd()))?;
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poll.deregister(&self.signals)
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}
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#[inline]
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fn reader(&mut self) -> &mut File {
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&mut self.file
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}
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#[inline]
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fn read_token(&self) -> mio::Token {
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self.token
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}
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#[inline]
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fn writer(&mut self) -> &mut File {
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&mut self.file
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}
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#[inline]
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fn write_token(&self) -> mio::Token {
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self.token
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}
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}
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impl EventedPty for Pty {
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#[inline]
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fn next_child_event(&mut self) -> Option<ChildEvent> {
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self.signals.pending().next().and_then(|signal| {
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if signal != sigconsts::SIGCHLD {
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return None;
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}
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match self.child.try_wait() {
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Err(e) => {
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error!("Error checking child process termination: {}", e);
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None
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},
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Ok(None) => None,
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Ok(_) => Some(ChildEvent::Exited),
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}
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})
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}
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#[inline]
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fn child_event_token(&self) -> mio::Token {
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self.signals_token
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}
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}
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impl OnResize for Pty {
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/// Resize the PTY.
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///
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/// Tells the kernel that the window size changed with the new pixel
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/// dimensions and line/column counts.
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fn on_resize(&mut self, window_size: WindowSize) {
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let win = window_size.to_winsize();
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let res = unsafe { libc::ioctl(self.file.as_raw_fd(), libc::TIOCSWINSZ, &win as *const _) };
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if res < 0 {
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die!("ioctl TIOCSWINSZ failed: {}", Error::last_os_error());
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}
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}
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}
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/// Types that can produce a `libc::winsize`.
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pub trait ToWinsize {
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/// Get a `libc::winsize`.
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fn to_winsize(self) -> winsize;
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}
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impl ToWinsize for WindowSize {
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fn to_winsize(self) -> winsize {
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let ws_row = self.num_lines as libc::c_ushort;
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let ws_col = self.num_cols as libc::c_ushort;
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let ws_xpixel = ws_col * self.cell_width as libc::c_ushort;
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let ws_ypixel = ws_row * self.cell_height as libc::c_ushort;
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winsize { ws_row, ws_col, ws_xpixel, ws_ypixel }
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}
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}
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unsafe fn set_nonblocking(fd: c_int) {
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use libc::{fcntl, F_GETFL, F_SETFL, O_NONBLOCK};
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let res = fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);
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assert_eq!(res, 0);
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}
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#[test]
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fn test_get_pw_entry() {
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let mut buf: [i8; 1024] = [0; 1024];
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let _pw = get_pw_entry(&mut buf).unwrap();
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}
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