pty

Easy Pseudo-Terminal Interface

Author

Alex Shinn

Documentation

PTY allows you to run sub-processes in pseudo-terminals and access their input and output from the controlling program as regular Chicken ports. This is useful for a variety of purposes, such as:

In general these cannot be done with regular sub-process ports.

High-Level Interface

[procedure] (call-with-pty-process-io command proc [name [width [height]]])

Call and return the result of proc which should be a procedure of three arguments: the input, output and PID of the sub-process command running in a new PTY. Ensures the sub-process is terminated on completion.

name, width and height are optional settings for the new PTY.

command may optionally be a list specifying the arglist to the sub-process, or a single string which is split on whitespace.

The ports generated only block the current thread, and char-ready? only returns #t if some input is already available. The eof-object is returned only when the sub-process terminates.

NOTE: Prior to login of, and after completion of the sub-process, anything written to the output port will pass directly through to the input port, which is almost certainly not what you want. To avoid premature writes, you should read once first. To avoid writing after the process has completed, don't write after you've read a single eof-object, or alternately you can check manually with process-alive?.

[procedure] (with-pty-process-io command proc [name [width [height]]])

As above, except current input and output ports are bound to the output and input of command respectively, and proc only takes one argument, the PID.

Low-Level Interface

[procedure] (open-pty-process command [name [width [height]]])
[procedure] (open-pty [name [width [height]]])
[procedure] (login-tty fd)
[procedure] (process-alive? pid)
[procedure] (fcntl-ref fd)
[procedure] (fcntl-set! fd arg)
[procedure] (file-select-one fd)
[procedure] (file-read/maybe fd buf len)
[procedure] (open-file-io/non-blocking fd [process-alive? (-> boolean)])

Example

(use pty)

(call-with-pty-process-io "ssh myfirewall"
  (lambda (in out pid)
    (peek-char in)
    (display (gui-get-password) out) ;; You'll need to implement this!
    (newline out)
    (read-line in)
    (display "dhclient 2>/dev/null && echo OK || echo FAIL\n" out)
    (unless (equal? "OK" (read-line in))
      (error "couldn't launch dhclient"))))

Changelog

License

 Copyright (c) 2006 Alex Shinn
 All rights reserved.
 
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