Version 12 of Expect for languages other than Tcl

Updated 2002-09-30 17:18:53

When Don Libes first created Expect, he assumed other languages would incorporate bindings relatively quickly. It's a testimony to the package's polish that no substantial efforts were made with other language bindings for many years; it's because his Expect has seemed so perfect, not for any lack of need other languages have.

By 2000, though, unripe Expect-like facilities were available for such languages as Perl and Python. In contrast to the situation for Tk, other languages have not created Expect modules by linking against Don's libraries; instead, they've written "from scratch" in more language-specific fashion.

Python has several Expect initiatives (just as it has a plethora of Web servers, GUI toolkits, and so on). Most advanced appears to be Pexpect [L1 ].

Expect.pm [L2 ]

How does the programming power of Tcl/Expect compare to that of the Expect modules of other languages? This comparison is far more difficult to explain than might first appear; full understanding involves several subtleties. Here are the highlights:

  • Tcl/Expect can do anything the others can do.
  • Tcl/Expect is more mature, and, in particular, better-behaved across a range of Unixes.
  • Tcl/Expect has exceptionally interesting and powerful channel-processing capabilities, and event-oriented ones in particular, that other Expects don't even attempt. However, only a small minority of Expect programmers ever use these. In fact, many (many) programmers make no more use of Expect than they would of the corresponding telnet module (telnetlib for Python).

[More detail.] [See essay on "Most programmers don't know what Expect can do for them".]

Because of its channel abstraction, Expect can interact with multiple processes quite easily. That has been more cumbersome or even infeasible with Expect extensions available for other languages.

Summary: Expect is generally "better" in the usual ways programmers understand that, compared to Expect-like modules for other languages, in:

  • the maturity of its pty management (there's a lot of OS-specific hair here);
  • interact
  • its facility with multiple managed processes or other I/O streams.
  • the book [...]
  • the on-line tutorials [...]
  • all the examples in the distribution and book

Category Expect