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Expect FAQ (Frequently Asked Questions)
 
An HTML version of this FAQ can be found in http://elib.cme.nist.gov/pub/expect/FAQ.html
 
This FAQ lists common questions, usually about subjects that didn't
fit well in the book for one reason or another (or weren't
indexed sufficiently well so that people can't find the answers easily
enough).  In some cases, I've left the original questions.  I suppose
I could've stripped off the headers, but it seems more realistic to
see actual people who've asked the questions.  Thanks to everyone who
asked.
 
The man page and the papers listed in the README file should
also be consulted for highly technical or philosophical discussion of
the implementation, design, and practical application of Expect.
 
Don
 
======================================================================
 
                Here is the list of questions.  You can search for the corresponding
                answer by searching for the question number.  For example searching
                for "#3." will get you that answer.
 
 
**** General ****
 
#1. I keep hearing about Expect.  So what is it?
#2. How do you pronounce "Ousterhout" anyway?  (Or "Libes" for that matter?)
 
#3. Why should I learn yet another language (Tcl) instead of
writing my interaction in .
#4. What about Perl?
#5. Do we need to pay or ask for permission to distribute Expect?
#6. Since Expect is free, can we give you a gift?
#7. Are there any hidden dangers in using Expect?
 
**** Book, newsgroup, FAQ, README, ... ****
 
#8. Why is this FAQ so short?
#9. The FAQ background makes the FAQ hard to read.
#10. Why isn't there an Expect mailing list?
#11. Why isn't overlay covered in Exploring Expect?
#12. Is the front cover of your book a self portrait (ha ha)?
#13. How are your daughter's kidneys?
#14. Are you going to have a book signing?
#15. How many books have you sold?
#16. I just want to tell you how much I like your book!
#17. Why don't the examples in your USENIX papers work?
#18. Can you put the examples in your book into an anonymous ftp site?
#19. Do you have ideas for more articles on Expect?
 
**** Can Expect do this? ****
 
#20. Can Expect automatically generate a script from watching a session?
#21. Can Expect understand screen-oriented (Curses) programs?
#22. Can Expect be run as a CGI script?
#23. Can Expect be run from cron?
 
**** Compilation or porting questions ****
 
#24. Why can't I compile Expect with Tcl 7.5?
#25. Why does Expect need to be setuid root on Cray?
#26. Does Expect run on VMS?
#27. Is it possible to use Expect and TclX together?
#28. Is it possible to use Expect and  together?
#29. Why does configure complain about "cross-compiling"?
#30. make/configure seems to be looping endlessly
#31. Compile fails with: Don't know how to make pty_.c
#32. Does Expect run on MSDOS, Win95, WinNT, MacOS, etc...
 
**** Other... ****
 
#33. Is it possible to prevent Expect from printing out its interactions?
#34. Why does it send back the same string twice?
#35. Why can't I send the line "user@hostname\r"?
#36. How do I hide the output of the send command?
#37. Why does "talk" fail with "Who are you?  You have no entry utmp" or
        "You don't exist.  Go away".
#38. Why does . match a newline?
#39. Why doesn't Expect kill telnet (or other programs) sometimes?
#40. How come I get "ioctl(set): Inappropriate ..., bye recursed" ...
#41. How come there's no interact function in the Expect library?
 
 
*
* Questions and Answers
*
 
 
 
**** General ****
 
 
#1. I keep hearing about Expect.  So what is it?
 
From: libes (Don Libes)
To: Charles Hymes 
Subject: I keep hearing about Expect.  So what is it?
 
Charles Hymes writes:
>
>So, what is Expect?
 
Expect is a tool primarily for automating interactive applications
such as telnet, ftp, passwd, fsck, rlogin, tip, etc.  Expect really
makes this stuff trivial.  Expect is also useful for testing these
same applications.  Expect is described in many books, articles,
papers, and FAQs.  There is an entire book on it available from
O'Reilly.
 
You can ftp Expect from ftp.cme.nist.gov as pub/expect/expect.tar.Z or ...gz
 
Expect requires Tcl.  If you don't already have Tcl, you can get it
in the same directory (above) as pub/expect/tcl.tar.Z or ...gz.
 
Expect is free and in the public domain.
 
Don
 
======================================================================
 
#2. How do you pronounce "Ousterhout" anyway?  (Or "Libes" for that matter?)
 
 
From: ouster@sprite.Berkeley.EDU (John Ousterhout)
To: libes@cme.nist.gov
Subject: Re: pronunciation?
Date: Tue, 29 May 90 21:26:10 PDT
 
Those of us in the family pronounce it "OH-stir-howt", where the
first syllable rhymes with "low", the second with "purr", and the
third with "doubt".  Unfortunately this isn't the correct Dutch
pronounciation for a name spelled this way (someplace along
the line it got misspelled:  it was originally "Oosterhout"), nor
is it what you'd guess if you use common sense.  So, we've gotten
used to responding to almost anything.
 
                                        -John-
 
I suppose I should say something in kind.  "Libes" is pronounced
"Lee-bis" with stress on the first syllable.  Like John though, I've
gotten used to responding to anything close.
 
By the way, notice the date on this message.  I had only written
the first cut of Expect four months earlier.  I asked John how to
pronounce his name because I had already got a paper accepted into
USENIX and needed to be able to say his name correctly while giving
the talk!
 
Don
 
======================================================================
 
#3. Why should I learn yet another language (Tcl) instead of
writing my interaction in .
 
From: libes (Don Libes)
To: Aamod Sane 
Subject: Re: Expect, Tcl, programmed dialogue etc.
Date: Mon, 2 Sep 91 15:47:14 EDT
 
>       >>A friend told me about "Expect". But then, I have to know the
>       >>idiocies of "tcl". I would like to know if there is an alternative
>       >>to Expect that is also useful in other places, so that I do not
>       >>have to spend time getting used to tcl for just this one tool.
>
>       Your reasoning is shortsighted.  Tcl is a language that can be used in
>       other applications.  It won't be a waste of your time to learn it.
>
>I have nothing against tcl as such.
>The reluctance to learn it comes mainly from the feeling that half my
>life seems to be spent learning new languages that differ very little
>from existing ones, and differ in annoying little details at that.
>To add to the misery, every implementation has its own
>idiosyncracies...:-(
 
Ironically, Tcl was written specifically to halt this very problem.
 
The author recognized that every utility seems to have its own
idiosyncratic .rc file or programming language.  Tcl was designed as a
general-purpose language that could be included with any utility, to
avoid having everyone hack up their own new language.
 
 In this context, your statements do Tcl a great disservice.
 
Don
 
======================================================================
 
#4. What about Perl?
 
From: libes (Don Libes)
To: Joe McGuckin 
Subject: Re: Need Perl examples
Date: Sun, 22 Jan 95 20:17:39 EST
 
Joe McGuckin writes:
>
>Yeah, I've scanned through your book a couple of times in the last
>week, trying to make up my mind if I should buy it.
 
I spent three years writing it - so I'm glad to hear you're spending a
little time considering its merit!
 
>Pro:
>   Looks like implementing some sort of telnet daemon would be trivial.
 
Once you see it as an Expect script, you'll realize how trivial
these things can really be.
 
>Con:
>   Yet another language to learn. I know perl reasonably well & would
>   like to stick with it.
 
Good point.  While I'm not a Perl guru, I've used it quite a bit
and it's nice for many things.  But I wouldn't have bothered writing
Expect in the first place if I thought Perl was ideal.  And many Perl
experts agree - I know a lot of them who call out to Expect scripts
rather than do this stuff in Perl - it's that much easier with Expect.
Expect is also much more mature.  It's portable, stable, robust, and
it's fully documented - with lots of examples and a complete tutorial,
too.
 
In response to someone complaining about how difficult it was to do
something in Perl, Larry Wall once remarked: "The key to using
Perl is to focus on its strengths and avoid its weaknesses."  That
definitely applies here.
 
Even if you do proceed with Perl, you will find the book
helpful.  Automating interactive applications has unique pitfalls to
it and many of the descriptions and solutions in the book transcend
the choice of language that you use to implement them.
 
Don
 
======================================================================
 
#5. Do we need to pay or ask for permission to distribute Expect?
 
From: libes (Don Libes)
To: Mohammad Reza Jahanbin 
Subject: Copyright Question.
Date: Tue, 26 Jan 93 23:46:24 EST
 
Mohammad Reza Jahanbin writes:
>Before anything let me thank you on behalf of ComputeVision R&D for
>putting so much effort into Expect. Part of CV has been using Expect
>for the past two years or so to build variety of tools including an
>automated testbed for a product.
>
>CV is currently considering shipping the automated testbed to some of its
>retailers, to enable them to perform their own tests before distributing
>the product.
>
>The Question is, are we allowed to ship Expect? Do we need to ask
>anyone for permission? Do we need to say or write anything in the
>documentation? Do we need to pay for it?
>
>I have not been able to find any copyright (or indeed copyleft) notices
>in the usual Expect distribution. Would you be able to clarify our position.
 
Sorry to delay in responding.  I sent your request to my management
and they had to discuss it (if they didn't, there would be no reason
to pay them).  While they continue to discuss it, I can tell you
informally the gist of what they will eventually say:
 
You are allowed to do just about anything with Expect.  You can even
sell it.  You need not ask our permission.  You need not pay for it.
(It is my understanding that your tax dollars, in effect, already have
paid for it.)
 
You should not claim that you wrote it (since this would be a lie), nor
should you attempt to copyright it (this would be fruitless as it is a
work of the US government and therefore not subject to copyright).
 
NIST would appreciate any credit you can give for this work.  One line
may suffice (as far as I'm concerned) although there should be
something to the effect that this software was produced for research
purposes.  No warantee, guarantee, or liability is implied.
 
My management is always interested in feedback on our work.  If you
would like to send letters of praise describing how Expect has helped
your business, we would be delighted.  Letters (on letterhead please)
are strong evidence used by policy makers when deciding where every
dollar goes.  If you want to send these letters to NIST directly, you
may send them to the following individuals:
 
Arati Prabahkar, Director
NIST
Admin Bldg, Rm A-1134
Gaithersburg, MD 20899
 
Ric Jackson, Manufacturing Engineering Laboratory
NIST
Bldg 220, Rm B-322
Gaithersburg, MD 20899
 
Howard Bloom, Manufacturing Systems Integration Division
NIST
Bldg 220, Rm A-127
Gaithersburg, MD 20899
 
Steve Ray, Manufacturing Collaboration Technologies Group
NIST
Bldg 220, Rm A-127
Gaithersburg, MD 20899
 
In case you're wondering about the uninformative titles, Arati Prabahkar is the
director of all of NIST (about 3000 people) and Steve Ray (way down there
at the bottom) is my immediate supervisor (and of 10 other very lucky people).
 
I hope this has answered your questions.  Let me know if you have
further questions.
 
Don
 
======================================================================
 
#6. Since Expect is free, can we give you a gift?
 
This is not an actual letter but represents the gist of several
that I've received.
 
>>>Expect has saved us many thousands of dollars.  We'd like to send
>>>you a free copy of our product.
>>
>>Thanks, but please don't.  As a federal employee, I'm not
>>allowed to accept gifts of any significant value.
>
>But, what if it is for personal use (like at home)? I assume
>that would be okay.
 
It doesn't matter (much).  What the rules address is whether a gift
might cause me to make an official decision differently.  This is
especially a concern because I may very well have to decide whether or
not to buy products from your company in the future.
 
There is a clause that says "you may accept gifts from friends,
regardless of value ... but you should be careful to avoid accepting
gifts which may create an appearance of impropriety, even if permitted
as an exception to the gift rules."
 
I'm still permitted to accept small token gifts, such as a t-shirt
or reasonably-priced dinner (under $20 per gift to a maximum of $50
per year from any person or company) - so things are not totally
ridiculous.  Although the precise values in the gift rules seem rather
arbitrary, I actually like the gift rules.  They stop a lot of the
nonsense that used to go on involving gifts.
 
Don
 
======================================================================
 
#7. Are there any hidden dangers in using Expect?
 
From: Charlton Henry Harrison 
To: libes@NIST.GOV
Date: Fri, 27 Jan 1995 23:30:56 -0600
 
>>>Dear Don:
>>>
>>>     I've been a fan of Expect ever since I first learned of UNIX back
>>>in late '93. I'm young and don't have my CS degree just yet, but I worked
>>>a while back at Texas Instruments in their Telecom Customer Support dept.
>>>I started in late '93 (and hence, that's where I first started exploring
>>>the UNIX environment) and immediately forsaw the need of automating a lot
>>>of my redundant and mindless duties, but I didn't know how since we were
>>>working over a heterogeneous LAN with multiple OSs.
>>>     Then I found out about Expect. I automated everything! My boss didn't
>>>like hearing that I was working on something else in order to get out of
>>>work, and I got tired of explaining it to him.
>>>     Although I accomplished all the aspects of my duties, I was infamous
>>>for being the laziest person at work, and it showed (I made my job SO easy).
>>>I got a new boss after a while, and he hated me from the start and fired
>>>me soon after. Oh well, I guess my mentality didn't click with theirs.
>>>     There are a lot of people like that: they believe life is putting
>>>in a hard day's work to get by. I hate that.
>>>     So the point is, thank you for the wonderful 'Expect'. I bought
>>>your book and now I have the most recent version of it on my Linux system
>>>at home. Needless to say I'm looking for another job, though.
>>>
>>>                                                     Charlton
>>>
>> Thanks very much for your nice letter.  Sorry to hear about your
>> automating yourself out of a job.  Actually, I think most computer
>> scientists have to face this dilemma.  In some ways, it's a
>> self-defeating occupation.
>>
>> Don
>
>Yeah, I'd be interested in hearing if you have a personal philosophy on
>how to handle this kind of thing. I plan on pursuing a career in Artificial
>Intelligence for similar reason of making life easier for everyone (me
>in particular!)  What the future holds in this category is a great
>mystery.
 
I'm glad you asked.  My personal philosophy on this kind of thing is:
Find someone really rich and marry them.
 
Don
 
======================================================================
 
**** Book, newsgroup, FAQ, README, ... ****
 
 
#8. Why is this FAQ so short?
 
From: libes (Don Libes)
To: Wade Holst 
Subject: Expect question
 
Wade Holst writes:
>
> 1) Is there a more up-to-date version of the FAQ than what
>    comes with expect-5.5?  (For such a useful application, I
>    would expect more than 12 questions).
 
I know that a lot of other packages have *huge* FAQs but I
have always believed that this is an indication that their regular
documentation sucks.  As questions arise that are not addressed well
by the original docs, the docs themselves should be fixed rather than
new ones created.
 
In contrast, I believe that an FAQ should literally be a list of
frequently asked questions and little else.  An FAQ should not be a
replacement for good documentation.
 
In that sense, I have tried to use this FAQ as a second place to
look rather than a first place.  The place you should always look
first is Exploring Expect.  At over 600 pages, the book is very
comprehensive, well-organized, and includes three indices and two
tables-of-contents to make it very easy to find what you want to know.
 
The book was not a rush job.  During the three years I spent
writing it, virtually every question I was asked became incorporated
as subject material for the book.  I wanted to make sure that the book
wouldn't need much of an FAQ!
 
It would not make sense to try and distill the entire book into an
FAQ (that is actually comprehensive rather that truly frequently asked
questions).  There's simply too much material there.
 
So this FAQ is short.  It really tries to stick just to *truly*
frequently asked questions.
 
Don
 
======================================================================
 
#9. The FAQ background makes the FAQ hard to read.
 
To: bonneau@mudd.csap.af.mil (Allen Bonneau)
Subject: FAQ background colors
Date: Wed, 10 Apr 96 10:24:52 EDT
 
Allen Bonneau writes:
>... the white and gray background makes the FAQ difficult to read.
 
It's not white and gray.  It's several very close shades of gray.
It's supposed to be very subtle.  Sounds like you have your browser in
a mode where it is mishandling colors.  Try turning on dithering.
 
Don
 
======================================================================
 
#10. Why isn't there an Expect mailing list?
 
From: libes (Don Libes)
To: dclark@nas.nasa.gov (David R. Clark)
Subject: Mailing list for Expect
Date: Mon, 23 Sep 91 18:21:28 EDT
 
>Would be nice if their were an Expect mailing list.  I would use it more
>often, and be made aware of other users.
 
Perhaps I'm too myopic, but I don't see the need for it.  Most of
the questions about Expect posted to Usenet every day can be found in
the various FAQs or in the book, so it's pretty easy getting
answers to them.
 
For one reason or another (occasionally a bug fix, but often, just
adding a neat example), I update Expect every couple of weeks.
Personally, I'd hate being on the other end of something like this.
Who needs patches every two weeks for problems that are likely not
even relevant to you?  (Most patches these days are either extremely
esoteric or are related to porting Expect to some unusual machine.)
 
>It would be helpful, too, if this served as an area for swapping programs.
>Many of the things that I want to do are done by others already.
 
Send me things that you'd like to distribute.  I can include it
with Expect or put it in a publicly accessible directory so other
people can get it.  I'm also willing to list links in Expect's home
page to other web pages about projects that use Expect.
 
There is a Tcl newsgroup, comp.lang.tcl, which many Expect users
read.  It's pretty good for asking questions about Tcl, and many of
the readers use Expect so Expect questions are encouraged.  The
newsgroup is gatewayed to a mailing list (tcl@sprite.berkeley.edu)
which is further described in the Tcl documentation.
 
Don
 
======================================================================
 
#11. Why isn't overlay covered in Exploring Expect?
 
From: libes (Don Libes)
To: spaf@cs.purdue.edu
Subject: Your book
 
Gene Spafford writes:
>I'm curious as to why the "overlay" command is not mentioned anywhere
>in the book.  Is that a recent addition?  A deprecated feature?  I
>ended up using it in one of my scripts....
 
The overlay command has been in Expect for a long time.  In all that
time no one has ever asked me about it and I have never used it.
Well, I used it once but I really didn't like the result, and so I
rewrote the script to not use it.  I left the overlay command in
Expect because it seemed like an interesting idea, but I never really
finished it - in the sense that I believe it needs some more options
and controls.  In comparison, the interact command is very flexible
and makes the need for overlay pretty moot.
 
Don
 
======================================================================
 
#12. Is the front cover of your book a self portrait (ha ha)?
 
From: libes (Don Libes)
To: pkinz@cougar.tandem.com (kinzelman_paul)
Subject: the cover?
 
kinzelman paul writes:
>The book finally came in. I tried to buy 4 copies but they had only 2
>left and they came in last Saturday. Move over Stephen King! :-)
 
4 copies!?  Wow.  That's more than my mother bought!
 
>I was discussing your book with somebody who stopped in and we began
>to speculate about the monkey on the cover. I don't suppose it's a
>self portrait? :-)
 
There is some real humor here.  There seems to be considerable
debate over what the creature is!  The colophon at the end of
the book says that it is a chimpanzee.  I like that idea much more
than a monkey which is what it looks like to me.  My wife, who has a
degree in zoology, explained to me that chimps are actually the second
smartest of primates (humans are the smartest).  Chimps are very
intelligent and can do many things (but not everything) that humans
do.  Perfect for describing Expect.  Anyway, she says I should be
honored to have it grace the book cover - even in theory.
 
I remarked to Edie (the cover designer at O'Reilly) that even though
the cover was nice looking, everyone was going to stare at it and say,
"Gee, but it looks like a monkey."  She replied "The purpose of the
cover is just to get people to pick the book up. This cover will do
that. Don't worry. If you get any rude comments from anyone, at least
you know they are paying attention."
 
[After being inundated by people pointing out that the animal
really is a monkey, O'Reilly subsequently decided to acquiesce and has
changed the colophon to admit that yes it is a rhesus monkey.
Evidentally, the book from which O'Reilly has been taking those
pictures from was wrong on this one.]
 
Don
 
======================================================================
 
#13. How are your daughter's kidneys?
 
From: libes
To: olav@emerson.physics.ubc.ca
Subject: How are your daughter's kidneys?
B. Olav Anderson writes:
>Don,
>
>I bought your book regarding expect and it's great and so is Expect.
>
>P.S. How's your daughters kidneys? I hope the're well hydrated :-)
 
In retrospect, I probably should have said that her "diapers" were
what was well-hydrated.  Glad to see that you found something in the
book worth reading!
 
Don
 
======================================================================
 
#14. Are you going to have a book signing?
 
From: libes (Don Libes)
To: Josef Sachs 
Subject: Expect
 
Josef Sachs writes:
>Do you have any book-signing sessions planned?
 
That's very ego-boosting to contemplate but I doubt that my name
is enough to draw the kind of crowd that would make it worthwhile.
I'll leave that kind of thing to Howard Stern.  Anyway, I have a
full-time job working for the government.  I doubt they would take too
kindly to me taking time off for self-aggrandizing.  (They weren't
particularly encouraging to have me write a book in the first place -
as you'll read in the Preface.)
 
I've written a couple of other books and people have mailed me those
for signatures.  (One guy sent me an entire box of books for
signatures - he was giving them to friends as Christmas gifts.)  If
you're similarly inclined, my address is in Expect's README file.  Or
if you're ever in my neck of the woods, feel free to stop by for a
chat (and bring your copy).
 
Don
 
======================================================================
 
#15. How many books have you sold?
 
From: Don Libes
To: Thomas Ragland 
Subject: Re: AIX smit automation
In-Reply-To: <199601092106.VAA19276@bugsy.aa.ans.net>
References: <199601092106.VAA19276@bugsy.aa.ans.net>
--text follows this line--
Thomas Ragland writes:
>  btw approximately how many books were sold?  I just bought
>  it and it is quite helpful.  Once again, thanks.
>
>Thomas
 
Glad you liked the book.  Sorry to disappoint you but I have no
idea about how many have been sold.  (I made my mother buy a couple,
so I know it's a positive number.)  Believe it or not, I try *not*
to pay attention to that type of thing.  I did with my first book
and was very disappointed.  (It sold well but it didn't earn that
first million that I was dreaming about...)  I've learned that I don't
write to sell books or make money.  If I did, I'd be better off
writing "Yet Another Book on HTML" or a romance novel.  No, the
real reason that I write is - I enjoy it.
 
Don
 
======================================================================
 
#16. I just want to tell you how much I like your book!
 
To: Joe Pasko 
Subject: Re: ***Expect spawn questions*****
Date: Thu, 15 Feb 96 14:52:23 EST
Joe Pasko writes:
>
>Thanks Don,
>
>I just took your advice and it was the tty settings. Thanks a bunch !
>
>As a side note: Great book !! It's the best howto for tcl-type stuff
>that I've seen around.
 
Thanks for the kind words.  But don't tell me (gee, I already like my
book!) - post your opinion to a newsgroup and send a review to a
magazine.  I regret that many Tcl users don't pick up the book simply
because they think it isn't of any use to the general Tcl user - which
of course isn't true.
 
Don
 
======================================================================
 
#17. Why don't the examples in your USENIX papers work?
 
From: libes (Don Libes)
To: Will Smith (AC) 
Subject: Expect
 
Will Smith (AC) writes:
>I just entered some scripts from a USENIX paper that my boss had.  I get
>errors about my quotes in the script.  Also, it doesn't seem to know
>about expect_match.  Thanks in advance for any insight you could offer.
 
The USENIX papers are old and out-of-date as far as quoting goes.  A
couple years ago, I cleaned up and simplified this aspect of Expect.
Similarly, expect_out is now where the results of expect's pattern
matching are saved.
 
The man page is always the best reference on what Expect currently
supports.  Alternatively, you can read the CHANGES files.  These files
document the changes from one major version to another.
 
Don
 
======================================================================
 
#18. Can you put the examples in your book into an anonymous ftp site?
 
From: libes (Don Libes)
To: pren@cs.umass.edu
Subject: Examples in your book "Exploring Expect"
 
Peifong Ren writes:
>
>Hi,
>
>I bought your book "Exploring Expect" from O'Reilly.
>I wonder can you put the eamples in your book into an anonymous ftp
>site?
 
All of the substantive examples come with recent versions of Expect.
Just look in the example directory.
 
The remaining 50 or so examples are short enough that typing them
in only takes a minute or two.  If I put them online, you'd spend more
time looking for them (reading my online catalog, figuring out what
the online descriptions meant, mapping them back to the file, etc.)
then it would take to type them in.  And since you're likely to want
to change the examples anyway, there's nothing to be gained for short
ones.
 
Don
 
======================================================================
 
#19. Do you have ideas for more articles on Expect?
 
From: libes (Don Libes)
To: faught@zeppelin.convex.com (Danny R. Faught)
Cc: libes
Subject: Re: SQA Quarterly articles
Date: Thu, 21 Dec 95 13:31:01 EST
 
Danny R. Faught writes:
>I just arranged to write an article on automating interactive
>processes for an issue early next year.  You have so many good pieces
>on expect out there, it's going to be hard to add anything original.
 
One thing I've never written is a good mini-tutorial.  Magazine
editors love these types of pieces and there's certainly a need for
it.  So I'd encourage that type of article.
 
Another possibility is an article on how you or your colleagues
personally applied Expect to solve your particular problem. Application-
oriented papers are the kind that necessarily have to be written by
people in the field who are applying the technology.  People love this
kind of practical paper.  For example, a good paper might be "Writing
a pager".  This is a nice topic because you can start with a simple
5-line script that solves the problem and then show progressive
refinements that handle different twists on the same problem.  (And
"how to write a pager" is a very frequently asked question on Usenet.)
 
Don
 
======================================================================
 
**** Can Expect do this? ****
 
 
#20. Can Expect automatically generate a script from watching a session?
 
From: libes (Don Libes)
To: pete@willow24.cray.com
Subject: Expect
Date: Fri, 12 Oct 90 17:16:47 EDT
 
>I like "Expect" and am thinking of using it to help automate the
>testing of interactive programs.  It would be useful if Expect had a
>"watch me" mode, where it "looks over the shoulder" of the user and
>records his keystrokes for later use in an Expect script.
>
>(Red Ryder and other Macintosh telecommunications packages offer this
>sort of thing.  You log onto Compuserve once in "watch me" mode, and
>RR keeps track of the keystrokes/prompts.  When you're done you have a
>script that can be used to log onto Compuserve automatically.)
>
>Before I look into adding a "watch me" feature, I thought I should
>ask: has this been done already?
>
>I'll say again that I like the tool a lot--nice work!  There are other
>people here using it for things like the testing of ksh, which
>responds differently to signals when not used interactively.
>
>-- Pete
 
The autoexpect script in Expect's example directory does what you
want.
 
Don
 
======================================================================
 
#21. Can Expect understand screen-oriented (Curses) programs?
 
Yes, it can - with a little clever scripting.  Look at the
term_expect script for an example.  It uses a Tk text widget to
support screen-oriented Expect commands.  This technique is described
very thoroughly in Chapter 19 of Exploring Expect.
 
Adrian Mariano (adrian@cam.cornell.edu) converted the term_expect
code (see above) so that it runs without Tk (exercise 4 in Chapter
19!)  Both term_expect and virterm can be found in the example
directory that comes with Expect.
 
An alternative approach to screen-handling was demonstrated by Mark
Weissman (weissman@gte.com) and Christopher Matheus who modified a
version of Expect to include a built-in Curses emulator.  It can be
ftp'd from the Tcl archive as expecTerm1.0beta.tar.Z.  (Note that
Expecterm does not run with the current version of Expect.)
 
I like the idea of keeping the curses emulator outside of Expect
itself.  It leaves the interface entirely defineable by the user.  And
you can do things such as define your own terminal types if you want.
For these reasons and several others, I'm not likely to return to
Expecterm.
 
Don
 
======================================================================
 
#22. Can Expect be run as a CGI script?
 
Expect scripts work fine as CGI scripts.  A couple pointers might
help to get you going:
 
Many Expect scripts can be run directly with one change - the
following line should be inserted before any other output:
 
puts "Content-type: text/html\n"
 
Be sure not to forget that extra newline at the end of the puts.
 
Next, make sure you invoke external programs using full paths.  For
example, instead of "spawn telnet", use "spawn /usr/ucb/telnet" (or
whatever).  Remember that the PATH and other environment variables are
going to be different than what you are used to.  This is very similar
to dealing with cron and you can get other good tips and advice from
reading the Background chapter in the book.
 
 One last tip: If a script runs fine by hand but not from CGI, just
log in as "nobody" to the host on which your CGI script runs.  Then
try running it by hand.  This generally makes it very obvious what's
going on.  (If you can't log in to the server or can't log in as
"nobody", use the kibitz trick described in the Background chapter.)
 
Don
 
======================================================================
 
#23. Can Expect be run from cron?
 
Expect itself works fine from cron - however, you can cause
problems if you do things that don't make sense in cron - such as
assume that there is a terminal type predefined.  There are a number
of other pitfalls to watch out for.  The list and explanations aren't
short - which is why there's a whole chapter ("Background") on the
subject in the book.
 
Here's one that someone tried to stump me with recently: They told
me that their program started up and then Expect immediately exited.
We spent a lot of time tracking this down (Was the spawned program
really starting up but then hanging - which would indicate a bug in
the program; or was the program NOT starting up - which would indicate
a bug in the environment; etc.)  Turned out that Expect wasn't even
running their program.  They had assumed cron honored the #! line
(which it doesn't) and so the first line in their script (exec date)
was being interpreted by the shell and of course, the script did
nothing after that - because that's what the shell's exec is supposed
to do!)
 
Don
 
======================================================================
 
**** Compilation or porting questions ****
 
 
#24. Why can't I compile Expect with Tcl 7.5?
 
You can - you just need a newer version of Expect.  Note that the
production release of Tcl 7.5 was just released and a compatible
Expect is still in beta.  So you shouldn't do this without
caution.
 
Expect 5.19 works fine with Tcl 7.4.  If you stay with Tcl 7.4, I
encourage you to upgrade to Expect 5.19 if you haven't already.
 
Don
 
======================================================================
 
#25. Why does Expect need to be setuid root on Cray?
 
From: libes (Don Libes)
To: u70217@f.nersc.gov (Lori Wong)
Subject: setuid in Expect
Date: Thu, 24 Oct 91 16:15:20 EDT
 
>     I have been running Expect now under UNICOS 6.1 and CSOS 1.0 (Cray
>Computer Corporation's OS).  The two machines that I am running Expect
>on have stringent security features, one of which is to limit setuid
>privileges to specific individuals.  I was wondering if you would be
>kind enough to explain the purpose of the setuid that is needed by Expect
>and whether it could be compiled to run without having to have setuid
>privilege?  I know it has to do with spawning and communicating with
>the various spawned tasks, but don't know enough of the details to be
>able to explain why Expect specifically needs setuid and whether or not
>it could cause a security problem (could someone use it to enter into
>the system and wreak havoc, for example?).  Right now, I've limited
>the access of Expect to my group, but need to know what the security
>implications are if I open it to all users.  I'd appreciate any light
>you can shed on this subject...
 
Root-access is needed to open a pty under Unicos.  Thus, all programs
accessing ptys must be setuid root.  If you do an "ls -l" of programs
like "script", "xterm", etc, you'll see this.
 
I have no idea why this is.  The requirement was probably for security
reasons to begin with, but it has the ironic effect of making more
programs require setuid and therefore greater possibility of errant
setuid programs.
 
In fact, there is one known Unicos bug relating to the way uids are
switched at exec time which requires further special coding.  If you
search for "Cray" in the Expect source you will see significant chunks
of code to get around the problem.
 
I don't know if this reassures you any.  All I can tell you is that a
number of Cray experts have looked into the situation and are happy
with the current implementation of Expect.
 
Don
 
======================================================================
 
#26. Does Expect run on VMS?
 
From: libes (Don Libes)
To: Cameron Laird 
Subject: VMS question.
 
Cameron Laird writes:
>Do you know of anyone working with Expect and VMS?
>I'd like not to re-invent wheels, but, if I'm to be
>the first one, I want others to benefit.
 
No, I'm not aware of anyone doing it.  Since VMS claims POSIX
conformance, it shouldn't be that hard - Expect uses the POSIX calls
if it can.  Probably the hardest part will just be modifying the Makefile
and the configure script!
 
However, that there might be a simpler solution.  The neat thing
about Expect is that you can control other computers easily.  Run
Expect on your UNIX box and have it log in to the VMS box and do its
thing.  (You can bypass the login garbage by using an inet daemon.)
We've done exactly this to a number of weird pieces of hardware we
have around the lab (robots, Lisp machines, embedded controllers, and,
of course, a VAX running VMS).  It saves time porting!
 
Don
 
======================================================================
 
#27. Is it possible to use Expect and TclX together?
 
Is it possible to use Expect and TclX together?
From: bfriesen@iphase.com (Bob Friesenhahn)
Date: 20 Jul 1994 04:09:43 GMT
Organization: Interphase Corporation, Dallas TX - USA
 
Jeffery A. Echtenkamp (echtenka@michigan.nb.rockwell.com) wrote:
: Do Expect and tclX work together? If so, must anything special be done to
: get them to work together?
 
This answer courtesy of Bob Friesenhahn, Interphase (bfriesen@iphase.com):
 
They work fine together.  However, you should prepend "exp_" to your Expect
command names.  This will ensure that there are no conflicts between Expect
commands and tclX commands of the same name (like wait).
 
Just pick up the "make-a-wish" package, follow the instructions, and you will
be all set.  I have built a wish based on tcl, tk, Expect, tclX, and dp using
this technique with no observed problems.
 
Bob
 
[If you need additional information, please read Chapter 22
("Expect as Just Another Tcl Extension") of Exploring Expect.  Its
sole focus is how to make Expect work with other extensions. - Don]
======================================================================
 
#28. Is it possible to use Expect and  together?
 
From: libes (Don Libes)
To: Frank Winkler 
Subject: Q Expect + TkSteal
 
Frank Winkler writes:
>Hi don,
>
>a short question considering installation of Expectk.
>
>Is it possible to build an Expectk-binary, which uses
>the features of BLT, TkSteal and Expect ?
 
I've never done it, but I know it must be possible because the tgdb
package in the Tcl archive uses all of those extensions with Expect.
 
Expect is a "well-behaved extension" in the sense that it requires no
changes to the Tcl core.  So Expect should work with any other Tcl
extensions.  You just need to add the usual Exp_Init call to main() or
the other _Init calls to Expect's main.
 
>If yes, which of them should be build first, second ... ?
 
Order doesn't matter.
 
I've done this kind of thing by hand.  It's pretty simple.  But people
tell me the make-a-wish package in the Tcl archive automates the
creation of multi-extension Tcl applications.
 
[Also see the answer to the previous FAQ answer.]
 
Don
 
======================================================================
 
#29. Why does configure complain about "cross-compiling"?
 
From: libes (Don Libes)
To: morton@hendrix.jci.tju.edu (Dan Morton)
Subject: Re: Sorry to bother you, but...
 
Dan Morton writes:
>Don,
>
>I've posted an inquiry to comp.lang.tcl about my configure problems with
>expect, but I've not yet gotten a reply.  Perhaps you can nudge me in the
>right direction?
>
>I'm running HP-UX 9.0 on a 735, and I've snagged the latest versions of Tcl
>and expect from NIST (7.4 and 5.18 respectively).  My gcc is v2.6.  Tcl
>configured and built out of the box, but I can't get expect to configure
>properly.  No matter what I do, it thinks it wants to cross-compile.  I
>think it's failing that little snippet of eval code.  It gets further if I
>specify --host=HP, but still complains about cross compiling.  Here's the
>result without options:
>
>{hendrix:~/expect-5.18:8} ./configure
>checking for gcc... gcc
>checking whether we are using GNU C... yes
>checking whether gcc accepts -g... no
>checking how to run the C preprocessor... gcc -E
>checking whether cross-compiling... yes
>checking whether cross-compiling... (cached) configure: error: You need to
>specify --target to cross compile,
>        or the native compiler is broken
 
I guess the error message has to be clearer.  The message:
 
        "or the native compiler is broken"
 
means that configure tried to compile a simple program and it failed.
Here's the program it tries to compile:
 
        main() {
                return(0);
        }
 
The configure output that you showed me says that it found gcc.
Perhaps it was misinstalled or is just a placeholder and doesn't
actually do anything?  Try compiling a tiny C program yourself from
the command line.
 
Don
 
======================================================================
 
#30. make/configure seems to be looping endlessly
 
To: Xiaorong Qu 
Subject: Make message for Expect
--text follows this line--
Xiaorong Qu writes:
>Don,
>
>The following is the output of make, you can find
>that the process repeated three times.
 
I bet what's going on is that your system clock is set to some
ridiculous time such as last year.  "Make" is sensitive to your clock.
Please fix your clock.  Then check that all the files are "older"
than the current time.  (If not, "touch" them all.)
 
Don
 
======================================================================
 
#31. Compile fails with: Don't know how to make pty_.c
 
From: libes (Don Libes)
To: wren@io.nosc.mil
Subject: Compile fails with: Don't know how to make pty_.c
 
>   I'm trying to compile Expect on hpux 9.01,
>   downloaded from ftp.cme.nist.gov expect.tar
 
>   after running config
>   the make fails with  "Don't know how to make pty_.c. (compile fails)
>   I see three versions pty_sgttyb.c, pty_termios.c and pty_unicos.c in
>   the load, but the configure picked none of them.
>   I tried forcing to pty_termios.c but that failed with other compile errors.
 
I've seen this happen because gcc was partially installed.  configure
finds the gcc stub and uses gcc for all the tests.  But because the
compiler doesn't work, every test fails so configure doesn't select
any of the choices.
 
So either finish installing gcc or delete the stub.
 
(And if it's not that, then something similar is wrong with whatever
compiler you've got.  Look closely at the output from configure, it
will tell you what compiler it is trying to use.)
 
By the way, Expect compiles fine on my HP (A.09.05 E 9000/735).
 
Don
 
======================================================================
 
#32. Does Expect run on MSDOS, Win95, WinNT, MacOS, etc...
 
From: libes (Don Libes)
To: Gerry_Jones@qmgateib.mitre.org
Subject: Does Expect run on ...
Date: Wed, 11 Oct 95 19:57:42 EDT
 
>I am in a group looking into developing script language-based applications for
>Mac and PC-Windows environments.  Our intent is to write scripts to work with
>interactive applications (e.g. telnet).  After asking around, I started
>looking into Tcl/Tk, which now have 'official' (?) (alpha) Mac and PC-Windows
>ports.  One of the people in our group has been working (in UNIX) with Tcl and
>Tk for quite some time, and said if there isn't an Expect port or similar tool
>for Mac and PC-Windows, then we shouldn't use Tcl/Tk; i.e. they would be too
>limited and/or require too much work to do what we need.  I've been cruising
>the Web for information, reading the Newsgroups, read the FAQs, etc., and have
>the following questions:
>
>1) Is there a current or planned port of Expect to Mac or PC-Windows
>environments?
 
No, Expect isn't currently portable to Windows or Mac.  Let me know
if you're seriously interested in a lot of work.  I'm not saying it's
not possible.  It's definitely possible and the porting work at Sun
has made it easier than before.  But it's still not a weekend hack.
Far from it.
 
I actually requested some time to work on it this year and
management said ("sure Don, go ahead") but I see now that they
approved approximately 65 weeks worth of projects for me for the
second half of the fiscal year.  (Yes, I'm serious, they really did.)
So I wouldn't hold my breath on this.  I'm really hoping someone
skilled with UNIX and NT volunteers some time.  Funding contributions
would also help.
 
If you are a student and would like a fun but demanding job for the
summer, let me know.  I'd be willing to let someone come up to speed
even if you don't already have all the skills.  And we offer
continuing internships if you'd like to come back for a semester or
two.  Pay is competitive.  Note: you must be a US citizen and you must
have good grades just to get through our personnel department.
 
Don
 
======================================================================
 
**** Other... ****
 
 
#33. Is it possible to prevent Expect from printing out its interactions?
 
From: libes (Don Libes)
To: Sunanda Iyengar 
Subject: Disabling display from Expect
 
Sunanda Iyengar writes:
>Is it possible to have Expect interact with a process and not print-out
>the results of interaction? In my application, I need it to go into a
>silent mode, communicate with a process without reporting to the user, and
>then come back to normal mode and  put the process into interactive mode.
 
Use the following command:
 
        log_user 0
 
To restore output:
 
        log_user 1
 
See the Expect man page for more details or page 175 of Exploring
Expect for details and examples.
 
Don
 
======================================================================
 
#34. Why does it send back the same string twice?
 
From: Don Libes
To: yusufg@himalaya.cc.gatech.edu (Yusuf Goolamabbas)
Subject: Duplicate pattern matches in Expectk
--text follows this line--
   Hi, I am trying to do a very simple thing in expectk
 
   spawn cat
   expect_background -re ".+" {
           send $expect_out(0,string)
   }
   exp_send "Hello World\n"
 
   Now the display in the text widget looks like this
   Hello World\r
   Hello World\r
 
   whereas I was expecting only one line
   Hello World\r
 
   Thanks in advance, Yusuf
   --
   Yusuf Goolamabbas                               yusufg@cc.gatech.edu
   Graphics, Visualization, & Usability Center     (O) 404.894.8791
   College of Computing Georgia Tech
   http://www.cc.gatech.edu/grads/g/Yusuf.Goolamabbas/home.html
 
This is correct behavior.  The first "Hello World" is echoed by the
terminal driver.  The second is echoed by cat.  This behavior has
nothing to do with Expectk (or Expect for that matter).  You can see
this same thing if you type to cat interactively.
 
% cat
Hello World
Hello World
 
In the example above, I typed "cat" at the shell prompt and pressed
return.  Then I entered "Hello World" and pressed return.  Looking at
the output I *see* "Hello World" twice even though I only entered it
once.
 
You can account for this behavior in your patterns.  Alternatively,
just turn off the echo.  In your particular case though, it's doing
the right thing, showing you the result of an interactive cat just as
if you had typed it yourself.
 
In practice, this kind of problem doesn't arise - because programs
like cat aren't spawned (except in very special situations).  I assume
that cat was just something you chose to experiment with.
 
Don
 
======================================================================
 
#35. Why can't I send the line "user@hostname\r"?
 
From: libes (Don Libes)
To: bt@nadine.hpl.hp.com
Subject: Re: [Q] Expect, ftp and '@'
 
>   I am attempting to use Expect to perform anonymous ftp gets without
>my having to type all the stuff --- I mean, waaaiiiting for the
>prompt, entering a-n-o-n-y-m-o-u-s with my fat fingers, and the rest.
>
>   But I have a probleme: as I set the password to be my e-mail address:
>   set password "bt@hplb.hpl.hp.com"
 
> the ftp servers seem not to receive neither my login name nor the
>at-sign. Some of them do not care, some others say "ok, but don't do
>that again", and the last ones throw me off.
 
The short answer is to upgrade to Expect 5.20 or later.  (Warning:
5.20 is still in beta.)  If you don't feel like doing this,
here's the explanation for older versions of Expect:
 
spawn initializes the terminal by using your current parameters and
then forces them to be "sane".  Unfortunately, on your system, "sane"
says to interpret the "@" as the line-kill character.
 
The most sensible thing to do is change "sane" in your Makefile to
something that makes sense.  (Since you work at HP, you might also
suggest that they modernize stty!)
 
Here's an example of a replacement line for the Makefile:
 
        STTY = -DDFLT_STTY=\""sane kill ^U"\"
 
Other alternatives are: quote the @, or use the -nottyinit flag, or
set the stty_init variable.
 
Don
 
======================================================================
 
#36. How do I hide the output of the send command?
 
From: tim@mks.com (Timothy D. Prime)
Subject: Re: hide the text of expect's send command?
Date: 29 Mar 1996 15:41:02 GMT
 
In article , Kirby Hughes  wrote:
> I don't want to see (on the screen) the text sent by a "send" command.  Is
> there a way to hide it?  "log_user 0" works for text coming back to me, but
> doesn't (seem to) work for sending...
>
> #!/usr/local/bin/expect --
> log_user 0
> spawn telnet proxy
> expect Command
> send "c [lrange $argv 0 1]\n"
> log_user 1
> interact
 
This answer courtesy of Timothy Prime, Mortice Kern Systems (tim@mks.com):
 
The output you are seeing wasn't printed by the send command.
(I.e., the log_user command is working just fine.)  The output you see
is from the interact command.  The interact command found program
output and thus wrote it to the terminal so that you could see it.
That's what the interact command is supposed to do!
 
Although the expanation might take a little thought, the solution is
easy.  Simply put an expect command in before the command "log_user 1".
Match against the last characters that you wish to suppress.
======================================================================
 
#37. Why does "talk" fail with "Who are you?  You have no entry utmp" or
        "You don't exist.  Go away".
 
From: libes (Don Libes)
To: Will Smith (AC) 
Subject: Expect
 
Will Smith (AC) writes:
>Hi there.  I was wondering if you had any ideas to why i am getting
>this problem running an Expect script which tries to spawn a talk
>process to myself on another machine. Would it have anything to do
>with the fact that the executables are NOT installed in /usr/local/bin
>or because it wasnt installed by ROOT or what. This is what my Expect
>script looks like.
>
>#! /home/ritchie/ops/william/test/expect -f
>
>spawn talk william@curiac.acomp
>set timeout 200
>expect {*established*}
>set send_human {.1 .3 1 .05 2}
>send -h "This is only a test.. I swear \ Please don't bust me with expect \n  >expect "{*\r*}"
>expect "{*\r*}"
>exec sleep 5
>send -h "Ok, well see ya tomorrow you idiot \n"
>exec sleep 3
>
>The error i get is that it returns this when i run the script.
>
>  Who are you? You have no entry in /etc/utmp! Aborting...
 
On most systems, Expect does not automatically make a utmp entry.  (A
utmp entry normally indicates login information which seems kind of
pointless for Expect scripts.)  This allows Expect to run non-setuid.
 
Normally, this lack of utmp entries doesn't mean much.  However, a few
programs actually refuse to run without a utmp entry.  Fortunately,
there are workarounds:
 
Program-dependent solutions:
 
"talk" is the only program I'm aware of that falls into this category.
One solution is to get ytalk.  ytalk doesn't have this problem plus it
fixes many other bugs in talk, such as being able to communicate with
both old and new talk.
 
Program-independent solutions:
 
Use a program specifically intended to create utmp entries.  Such
programs are easy to write or get if you don't have them already.  For
instance, sessreg is one which comes with the xdm distribution.  And
Solaris uses utmp_update.  I like this approach because it isolates
the setuid code in a small single system utility rather than in every
program on the system that needs this ability.
 
Don
 
======================================================================
 
#38. Why does . match a newline?
 
From: libes (Don Libes)
To: xipr@alv.teli.se (Ivan Prochazka)
Subject: Why does . match a newline?
Ivan Prochazka writes:
>
>Hello Don.
>
>In my opinion(and emacs) the regexp-symbol "." stands for all
>characters except newline(\n).
>This is not the case in Expect 5.2.
 
Yes, there are some packages that follow this convention, but I don't
think it is appropriate for Expect.  Unlike emacs, most Expect
patterns don't look for full lines - more often they look for prompts
which *don't* end with newlines.
 
I find that I actually write the [^\n] pattern very rarely.  And
if I write it frequently in a script, then the expect itself probably
ought to be in a subroutine.
 
In fact, the more common line-terminating sequence in Expect is \r\n,
so that might make a more likely argument.  In any case, Expect
defines . the way POSIX does.  So I feel pretty good about the
definition of . being what it is.
 
Don
 
======================================================================
 
#39. Why doesn't Expect kill telnet (or other programs) sometimes?
 
From: libes (Don Libes)
To: Karl.Sierka@Labyrinth.COM
Subject: Re: need help running telnet Expect script from cron on sunos 4.1.3
 
karl.sierka@labyrinth.com writes:
>       The only problem I am still having with the script I wrote is that
>    the telnet does not seem to die on it's own, unless I turn on debugging.
 
Actually, Expect doesn't explicitly kill processes at all.  Generally,
processes kill themselves after reading EOF on input.  So it just seems
like Expect kills all of its children.
 
>    I was forced to save the pid of the spawned telnet, and kill it with an
>    'exec kill $pid' in a proc that is hopefully called before the script
>    exits. This seems to work fine, but it makes me nervous since omnet
>    charges for connect time, and leaving a hung telnet lying around could
>    get expensive. I warned the rest of the staff so that they will also be
>    on the lookout for any possible hung telnets to omnet.
 
The problem is that telnet is not recognizing EOF.  (This is quite
understandable since real users can't actually generate one from the
telnet user interface.)  The solution is to either 1) explicitly drive
telnet to kill itself (i.e., a graceful logout) followed by "expect
eof" or 2) "exec kill" as you are doing.
 
This is described further in Exploring Expect beginning on page 103.
 
Don
 
======================================================================
 
#40. How come I get "ioctl(set): Inappropriate ..., bye recursed" ...
 
From: libes (Don Libes)
To: james@Solbourne.COM (James B. Davis)
Subject: How come I get "ioctl(set): Inappropriate ..., bye recursed" ...
Date: Tue, 10 Dec 91 10:47:21 MST
 
>Every time I ^C out of a Expect script run I get:
>
>ioctl(set): Inappropriate ioctl for device
>bye recursed
>
>james@solbourne.com
 
This answer courtesy of Michael Grant (mgrant@xdr.ncsl.nist.gov):
 
You (or whoever installed gcc) forgot to run the fixincludes shell
script while installing gcc.  Recompiled gcc with itself, then run the
fixincludes script - and the messages will go away.
 
Michael Grant
======================================================================
 
#41. How come there's no interact function in the Expect library?
 
From: libes (Don Libes)
To: Djamal SIMOHAND 
Subject: Re: exp_expectl
Date: Wed, 3 Jan 96 12:17:01 EST
 
Djamal SIMOHAND writes:
>I have already used the Expect program to write a script to connect by
>telnet on my machine.  Now I made a graphic interface in C and I need
>the expect in C in order to have a coherent executable.
>
>I've already written most of the C already, but the connection is
>closed just after my program is finished.  Then I have no opportunity
>to work on my machine.  It seems I need of the equivalent of
>"interact" in C.  Is there such a function in the C library?
>
>Thanks for your help,
>                                                      Djamal
 
No, there is no interact-like function in the C library.  The reason
is three-fold:
 
1) It is simple enough to write your own.  It's just a loop after
all:
 
        while 1 {
                select/poll()
                read()
                write()
        }
 
2) There's no way I could possibly provide all the options you might
need.  In Expect, it's not a problem because the environment is very
controlled, but in C, it's impossible to control what you might want
to do.  For example, you mention that you're embedding your code in a
graphics application.  Graphics packages typically have their own
event manager, so you wouldn't want a monolithic interact function.
 
3) The library is intended for embedding in other applications, where
it rarely makes sense to give the user direct control of a spawned
process.  That kind of thing makes so much more sense to handle with
an Expect script than a C program.  The C library was not intended as
a replacement for Expect.  Expect is really the tool of choice for
interaction problems, not C.
 
In summary, there's very little payoff for the library to supply an
interact function.  A simple one would only satisfy people who should
be using Expect anyway - and it's impossible to create one that would
do everything that everyone wants.  It's easier just to let people
roll their own.
 
Don
 
======================================================================
 
 
Names of companies and products, and links to commercial pages are
provided in order to adequately specify procedures and equipment used.
In no case does such identification imply recommendation or
endorsement by the National Institute of Standards and Technology, nor
does it imply that the products are necessarily the best available for
the purpose.
 
Last edited: Thu Jun  6 07:35:19 EDT 1996 by Don Libes
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