# module PTY

Creates and manages pseudo terminals (PTYs). See also en.wikipedia.org/wiki/Pseudo_terminal

`PTY` allows you to allocate new terminals using `::open` or `::spawn` a new terminal with a specific command.

## Example¶ ↑

In this example we will change the buffering type in the `factor` command, assuming that factor uses stdio for stdout buffering.

If `IO.pipe` is used instead of `PTY.open`, this code deadlocks because factor's stdout is fully buffered.

    # start by requiring the standard library PTY
    require 'pty'

    master, slave = PTY.open
    read, write = IO.pipe
    pid = spawn("factor", :in=>read, :out=>slave)
    read.close     # we dont need the read
    slave.close    # or the slave

    # pipe "42" to the factor command
    write.puts "42"
    # output the response from factor
    p master.gets #=> "42: 2 3 7\n"

    # pipe "144" to factor and print out the response
    write.puts "144"
    p master.gets #=> "144: 2 2 2 2 3 3\n"
    write.close # close the pipe

    # The result of read operation when pty slave is closed is platform
    # dependent.
    ret = begin
            master.gets     # FreeBSD returns nil.
          rescue Errno::EIO # GNU/Linux raises EIO.
            nil
          end
    p ret #=> nil

## License¶ ↑

    C) Copyright 1998 by Akinori Ito.

    This software may be redistributed freely for this purpose, in full
    or in part, provided that this entire copyright notice is included
    on any copies of this software and applications and derivations thereof.

    This software is provided on an "as is" basis, without warranty of any
    kind, either expressed or implied, as to any matter including, but not
    limited to warranty of fitness of purpose, or merchantability, or
    results obtained from use of this software.

### Public Class Methods

check(pid, raise = false) → Process::Status or nil click to toggle source
check(pid, true) → nil or raises PTY::ChildExited

Checks the status of the child process specified by `pid`. Returns `nil` if the process is still alive.

If the process is not alive, and `raise` was true, a `PTY::ChildExited` exception will be raised. Otherwise it will return a `Process::Status` instance.

`pid`

  The process id of the process to check

`raise`

  If `true` and the process identified by `pid` is no longer alive a `PTY::ChildExited` is raised.

    static VALUE
    pty_check(int argc, VALUE *argv, VALUE self)
    {
        VALUE pid, exc;
        rb_pid_t cpid;
        int status;
        const int flag =
    #ifdef WNOHANG
            WNOHANG|
    #endif
    #ifdef WUNTRACED
            WUNTRACED|
    #endif
            0;

        rb_scan_args(argc, argv, "11", &pid, &exc);
        cpid = rb_waitpid(NUM2PIDT(pid), &status, flag);
        if (cpid == -1 || cpid == 0) return Qnil;

        if (!RTEST(exc)) return rb_last_status_get();
        raise_from_check(cpid, status);

        UNREACHABLE_RETURN(Qnil);
    }

spawn(command_line) { |r, w, pid| ... } click to toggle source
spawn(command_line) → [r, w, pid]
spawn(command, arguments, ...) { |r, w, pid| ... }
spawn(command, arguments, ...) → [r, w, pid]

Spawns the specified command on a newly allocated pty. You can also use the alias `::getpty`.

The command's controlling tty is set to the slave device of the pty and its standard input/output/error is redirected to the slave device.

`command` and `command_line` are the full commands to run, given a `String`. Any additional `arguments` will be passed to the command.

### Return values¶ ↑

In the non-block form this returns an array of size three, `[r, w, pid]`.

In the block form these same values will be yielded to the block:

`r`

  A readable `IO` that contains the command's standard output and standard error

`w`

  A writable `IO` that is the command's standard input

`pid`

  The process identifier for the command.

    static VALUE
    pty_getpty(int argc, VALUE *argv, VALUE self)
    {
        VALUE res;
        struct pty_info info;
        rb_io_t *wfptr,*rfptr;
        VALUE rport = rb_obj_alloc(rb_cFile);
        VALUE wport = rb_obj_alloc(rb_cFile);
        char SlaveName[DEVICELEN];

        MakeOpenFile(rport, rfptr);
        MakeOpenFile(wport, wfptr);

        establishShell(argc, argv, &info, SlaveName);

        rfptr->mode = rb_io_modestr_fmode("r");
        rfptr->fd = info.fd;
        rfptr->pathv = rb_obj_freeze(rb_str_new_cstr(SlaveName));

        wfptr->mode = rb_io_modestr_fmode("w") | FMODE_SYNC;
        wfptr->fd = rb_cloexec_dup(info.fd);
        if (wfptr->fd == -1)
            rb_sys_fail("dup()");
        rb_update_max_fd(wfptr->fd);
        wfptr->pathv = rfptr->pathv;

        res = rb_ary_new2(3);
        rb_ary_store(res,0,(VALUE)rport);
        rb_ary_store(res,1,(VALUE)wport);
        rb_ary_store(res,2,PIDT2NUM(info.child_pid));

        if (rb_block_given_p()) {
            rb_ensure(rb_yield, res, pty_detach_process, (VALUE)&info);
            return Qnil;
        }
        return res;
    }

open → [master_io, slave_file] click to toggle source
open {|master_io, slave_file| ... } → block value

Allocates a pty (pseudo-terminal).

In the block form, yields two arguments `master_io, slave_file` and the value of the block is returned from `open`.

The `IO` and `File` are both closed after the block completes if they haven't been already closed.

    PTY.open {|master, slave|
      p master      #=> #<IO:masterpty:/dev/pts/1>
      p slave      #=> #<File:/dev/pts/1>
      p slave.path #=> "/dev/pts/1"
    }

In the non-block form, returns a two element array, `[master_io, slave_file]`.

    master, slave = PTY.open
    # do something with master for IO, or the slave file

The arguments in both forms are:

`master_io`

  the master of the pty, as an `IO`.

`slave_file`

  the slave of the pty, as a `File`. The path to the terminal device is available via `slave_file.path`

`IO#raw!` is usable to disable newline conversions:

    require 'io/console'
    PTY.open {|m, s|
      s.raw!
      ...
    }

    static VALUE
    pty_open(VALUE klass)
    {
        int master_fd, slave_fd;
        char slavename[DEVICELEN];
        VALUE master_io, slave_file;
        rb_io_t *master_fptr, *slave_fptr;
        VALUE assoc;

        getDevice(&master_fd, &slave_fd, slavename, 1);

        master_io = rb_obj_alloc(rb_cIO);
        MakeOpenFile(master_io, master_fptr);
        master_fptr->mode = FMODE_READWRITE | FMODE_SYNC | FMODE_DUPLEX;
        master_fptr->fd = master_fd;
        master_fptr->pathv = rb_obj_freeze(rb_sprintf("masterpty:%s", slavename));

        slave_file = rb_obj_alloc(rb_cFile);
        MakeOpenFile(slave_file, slave_fptr);
        slave_fptr->mode = FMODE_READWRITE | FMODE_SYNC | FMODE_DUPLEX | FMODE_TTY;
        slave_fptr->fd = slave_fd;
        slave_fptr->pathv = rb_obj_freeze(rb_str_new_cstr(slavename));

        assoc = rb_assoc_new(master_io, slave_file);
        if (rb_block_given_p()) {
            return rb_ensure(rb_yield, assoc, pty_close_pty, assoc);
        }
        return assoc;
    }

spawn(command_line) { |r, w, pid| ... } click to toggle source
spawn(command_line) → [r, w, pid]
spawn(command, arguments, ...) { |r, w, pid| ... }
spawn(command, arguments, ...) → [r, w, pid]

Spawns the specified command on a newly allocated pty. You can also use the alias `::getpty`.

The command's controlling tty is set to the slave device of the pty and its standard input/output/error is redirected to the slave device.

`command` and `command_line` are the full commands to run, given a `String`. Any additional `arguments` will be passed to the command.

### Return values¶ ↑

In the non-block form this returns an array of size three, `[r, w, pid]`.

In the block form these same values will be yielded to the block:

`r`

  A readable `IO` that contains the command's standard output and standard error

`w`

  A writable `IO` that is the command's standard input

`pid`

  The process identifier for the command.

    static VALUE
    pty_getpty(int argc, VALUE *argv, VALUE self)
    {
        VALUE res;
        struct pty_info info;
        rb_io_t *wfptr,*rfptr;
        VALUE rport = rb_obj_alloc(rb_cFile);
        VALUE wport = rb_obj_alloc(rb_cFile);
        char SlaveName[DEVICELEN];

        MakeOpenFile(rport, rfptr);
        MakeOpenFile(wport, wfptr);

        establishShell(argc, argv, &info, SlaveName);

        rfptr->mode = rb_io_modestr_fmode("r");
        rfptr->fd = info.fd;
        rfptr->pathv = rb_obj_freeze(rb_str_new_cstr(SlaveName));

        wfptr->mode = rb_io_modestr_fmode("w") | FMODE_SYNC;
        wfptr->fd = rb_cloexec_dup(info.fd);
        if (wfptr->fd == -1)
            rb_sys_fail("dup()");
        rb_update_max_fd(wfptr->fd);
        wfptr->pathv = rfptr->pathv;

        res = rb_ary_new2(3);
        rb_ary_store(res,0,(VALUE)rport);
        rb_ary_store(res,1,(VALUE)wport);
        rb_ary_store(res,2,PIDT2NUM(info.child_pid));

        if (rb_block_given_p()) {
            rb_ensure(rb_yield, res, pty_detach_process, (VALUE)&info);
            return Qnil;
        }
        return res;
    }