Expect FAQ (Frequently Asked Questions)
An HTML version of this FAQ can be found in http://expect.nist.gov/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. How was this FAQ created?
#10. The background makes the FAQ hard to read.
#11. Why isn't there an Expect mailing list?
#12. Why isn't overlay covered in Exploring Expect?
#13. Is the front cover of your book a self portrait (ha ha)?
#14. Why don't the examples in your USENIX papers work?
#15. Can you put the examples in your book into an anonymous ftp site?
#16. Do you have ideas for more articles on Expect?
**** Can Expect do this? ****
#17. Can Expect automatically generate a script from watching a session?
#18. Can Expect understand screen-oriented (Curses) programs?
#19. Can Expect be run as a CGI script?
#20. Can Expect act like a browser and retrieve pages or talk to a CGI script?
#21. Can Expect be run from cron?
#22. Why does my Expect script not work under inetd?
**** Compilation or porting questions ****
#23. Why can't I compile Expect with Tcl 8.0?
#24. Does Expect 5.26 work with Tcl/Tk 8.0.3?
#25. Why can't I compile Expect with Tcl/Tk 8.1aX?
#26. Why can't I compile Expect with Tcl/Tk 8.0b1?
#27. Why does Expect need to be setuid root on Cray?
#28. Does Expect run on VMS?
#29. Is it possible to use Expect and TclX together?
#30. Is it possible to use Expect and together?
#31. Why does configure complain about "cross-compiling"?
#32. Why are make/configure looping endlessly?
#33. Why does compile fail with: Don't know how to make pty_.c?
#34. Does Expect run on MSDOS, Win95, WinNT, MacOS, etc...?
#35. Why does Expect dump core? Why can I run Expect as root but not as myself?
**** Other... ****
#36. Is it possible to prevent Expect from printing out its interactions?
#37. Why does it send back the same string twice?
#38. Why can't I send the line "user@hostname\r"?
#39. How do I hide the output of the send command?
#40. Why don't I see pauses between characters sent with send -s?
#41. Why does "talk" fail with "Who are you? You have no entry utmp" or
"You don't exist. Go away"?
#42. Why does . match a newline?
#43. Why doesn't Expect kill telnet (or other programs) sometimes?
#44. How come I get "ioctl(set): Inappropriate ..., bye recursed"?
#45. How come there's no interact function in the Expect library?
#46. Can't you make tkterm understand any terminal type?
#47. Trapping SIGCHLD causes looping sometimes
#48. Why do I get "invalid spawn id"?
#49. Could you put a version number in the filename of the Expect archive?
#50. Why does Expect work as root, but say "out of ptys" when run as myself?
#51. Why does spawn fail with "sync byte ...."?
#52. Why does Expect fail on RedHat 5.0?
#53. Why does Expect fail on RedHat 5.1?
#54. Is Expect Y2K compliant?
*
* 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.
Expect is free and in the public domain. Download instructions can
be found in the Expect homepage.
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)
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.
It is my understanding that 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. (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:
Robert Hebner, Director
NIST
Admin Bldg, Rm A-1134
Gaithersburg, MD 20899
Ric Jackson, Manufacturing Engineering Laboratory
NIST
Bldg 220, Rm B-322
Gaithersburg, MD 20899
Steve Ray, Manufacturing Systems Integration Division
NIST
Bldg 220, Rm A-127
Gaithersburg, MD 20899
Amy Knutilla, Manufacturing Collaboration Technologies Group
NIST
Bldg 220, Rm A-127
Gaithersburg, MD 20899
In case you're wondering about the uninformative titles, Robert Hebner
is the director of all of NIST (about 3000 people) and
Amy Knutilla (way down there at the bottom) is my immediate supervisor.
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. How was this FAQ created?
The Expect FAQ is regularly recreated by a Tcl script which
produces either text or HTML depending on how it is called. Using Tcl
has two nice results:
+ I didn't have to choose one format and worry about
converting it to the other. (Remember that the FAQ appears in HTML on
the web and it appears in text in the Expect distribution.) The more
common approach - doing conversions in either direction - is really
painful - plus, it's now easy to generate other formats, too.
+ It's much, much easier to keep track of questions and
answers. For example, when I add a new question, I don't have to add
it twice (once at the top and again later with the answer), nor do I
have to worry about making the links between them. All this and a lot
of other stuff is handled automatically - and the source is much more
readable than the actual HTML.
(see "FAQbuilder")
You can read about these ideas in a paper that appeared at Tcl '96
called Writing CGI Scripts in Tcl. (CGI scripts are the primary focus of the
paper, but it also spends time on HTML generation for other purposes -
including the example of highly stylized documents like FAQs.)
I encourage you to examine the source to this FAQ - it
comes in two parts:
+ Expect-specific FAQ source
+ Generic FAQ Builder source
The generic FAQ builder has also been used to build several other
FAQs (unrelated to Expect).
Don
======================================================================
#10. The 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. Turn on dithering and
restart your browser.
Don
======================================================================
#11. 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.
NIST doesn't distribute software written by other people but if
you've got relatively small scripts that show off unique ideas and
techniques that would be educational for the Expect community, I can
include your script 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
======================================================================
#12. Why isn't overlay covered in Exploring Expect?
To: spaf@cs.purdue.edu
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
======================================================================
#13. 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 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
======================================================================
#14. 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
======================================================================
#15. 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
======================================================================
#16. 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? ****
#17. 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
======================================================================
#18. 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
======================================================================
#19. 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.
Another 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.)
You may find it helpful to use cgi.tcl, a nice collection of
CGI support utilities for Tcl scripts. It includes an Expect example
among many others. The package includes just about everything:
tables, frames, cookies, file upload, etc...., with some nice
debugging support. It's pure Tcl, no C code - so it's very easy to
try out and use.
Don
======================================================================
#20. Can Expect act like a browser and retrieve pages or talk to a CGI script?
From: jasont@netscape.com (Jason Tu)
Date: Sat, 02 Nov 1996 09:51:03 -0800
I read your book "Exploring Expect" and find Expect is just the tool
to test Netscape's enterprise server product, since it is very easy to
use and quick to develop. I figured I would use telnet to send HTTP
protocol dialog to a HTTP server and simulate how it behaves. But I
couldn't get it to work at all. I am wondering that there might be a
quick example that you can share with me.
Yes, this is a useful way of testing HTTP servers and running CGI
scripts (and winning Web contests :-). You can add error checking and
other stuff, but here's the minimum your script should have to read a
web page:
match_max 100000
set timeout -1
spawn telnet $host 80
expect "Escape character is *\n"
send "GET $page\r\n"
expect
puts "$expect_out(buffer)"
If you want to communicate information to a CGI script, you'll want
more. One way to see what needs to be sent is to load a real browser
with the form and then send it to a fake daemon such as this one:
#!/bin/sh
/bin/cat -u > /tmp/catlog
Enable this by adding this service to inetd. Then save the form in
a temporary file, modify the form's host and port to correspond to
your own host and whatever port you've chosen to associate with your
fake daemon. Now fill out the form and you'll find the form data in
/tmp/catlog. Using this, you can determine exactly how to amend your
Expect script to behave like your browser.
Don
======================================================================
#21. 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
======================================================================
#22. Why does my Expect script not work under inetd?
From: dpm@bga.com (David P. Maynard)
Subject: Re: Tcl/Expect, inetd service, and no echo password
Date: 24 Oct 1996 13:34:57 -0500
In article <54ocsh$9i1@urchin.bga.com> dpm@bga.com (David P. Maynard) writes:
I am fairly new to expect, so hopefully this isn't too obvious. I also
confess to not having looked in "Exploring Expect" becuase I haven't
found it in stock at a local bookstore yet.
I want to write an expect script that runs as a service from inetd.
(Actually, I plan to use the tcpd 'twist' command to launch the
binary, but that doesn't seem to affect the problem.) The script will
prompt the user for a password. The supplied password is used as a
key to decrypt some passwords stored online. The script then fires
off a telnet session to a remote box and does some fairly simple
things that require the decrypted passwords.
I have all of this working when I run the script from a UNIX prompt.
However, when I run it out of inetd, the 'stty -echo' commands that
turn off character echo when the user types the password fail with the
following error:
stty: impossible in this context
are you disconnected or in a batch, at or cron script?
stty: ioctl(user): Bad file descriptor
I can understand the cause of the message (no associated tty), but I
can't think of an easy solution. If I use 'gets' or 'expect_user,'
the user's input is always echoed. I tried a few variations on the
stty command, but didn't have any luck.
Any suggestions?
Yes, read Exploring Expect, Chapter 17 (Background Processing). In
the section "Expect as a Daemon", there's a very thorough discussion
of this problem and how to solve it.
In short, there's no tty when you run a process from inetd. Echoing
is controlled by the telnet protocol, so you must send and expect
telnet protocol packets to solve the problem. Even knowing this, the
actual implementation is very non-obvious which is why the book goes
into it in such detail.
Don
======================================================================
**** Compilation or porting questions ****
#23. Why can't I compile Expect with Tcl 8.0?
Sounds like you have an old version of Expect. Get a a new version of Expect.
Don
======================================================================
#24. Does Expect 5.26 work with Tcl/Tk 8.0.3?
To: aspi@cisco.com
Subject: Re: Expect 5.26 and TCL 8.0
Aspi Siganporia writes:
>
>Hi Don,
>
>We are looking at upgrading Expect. Our last version was Expect5.22
>
>I see that Expect5.26 supports TCL 8.0.
>
>The question is,
>
>Will it work with TCL8.0.3?
>
>Thanks
>Aspi
It might. 8.0.3 broke a couple of the more esoteric configurations.
If you find that you can't compile using 5.26, get 5.27.
Don
======================================================================
#25. Why can't I compile Expect with Tcl/Tk 8.1aX?
Historically, I've rarely found the time to port Expect to alphas
and betas. I recommend you stick with 8.0 unless you're willing to do
a little work.
Don
======================================================================
#26. Why can't I compile Expect with Tcl/Tk 8.0b1?
I don't see the point in supporting an old beta. Upgrade to the
production release of Tcl/Tk 8.0.
Don
======================================================================
#27. 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
======================================================================
#28. 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
======================================================================
#29. 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]
======================================================================
#30. 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
======================================================================
#31. 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
======================================================================
#32. Why are make/configure 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
======================================================================
#33. Why does compile fail 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
======================================================================
#34. Does Expect run on MSDOS, Win95, WinNT, MacOS, etc...?
Gordon Chaffee has ported Expect to NT. I would like to unify the
UNIX and NT code but I probably won't have the time to do this
personally. Volunteers are welcome.
I have no plans to do other ports. Feel free to volunteer.
Don
======================================================================
#35. Why does Expect dump core? Why can I run Expect as root but not as myself?
From: Wayne Tcheng
Subject: Expect on Solaris
Date: Wed, 2 Apr 97 21:34:50 EST
I've compiled Expect 5.21 with Tcl 7.6 and Tk 4.2. Whenever I run Expect
as a non-root user, it core dumps. When I am root, I can run it
successfully. However, if I "su - wmt" to my own id, I can also run it
without a problem. I've tried making the expect binary suid root, but
that does not help either. I'm on Solaris 2.5. Any ideas?
Sounds like something on your system is misconfigured. Everytime
I've had reports like this (works as root, not as user), it's turned
out to be /tmp was unwriteable or something equally improbable.
The easiest way to find out is to use the debugger and tell me where
Expect is dumping core. (If you don't understand this statement, ask
a local C or C++ programmer.)
As an aside, you should be using the most recent version of Expect
(currently 5.22.1). But I don't know of any problems in 5.21 that
caused core dumps, so it's certainly worth trying the debugger
approach before retrieving the latest version. But if you do find a
bug in Expect, before reporting it, please verify that it still exists
in the current version.
Don
======================================================================
**** Other... ****
#36. 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
======================================================================
#37. 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
======================================================================
#38. 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. 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
======================================================================
#39. 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.
======================================================================
#40. Why don't I see pauses between characters sent with send -s?
From: jcarney@mtl.mit.edu (John C. Carney)
Newsgroups: comp.lang.tcl
Date: 12 Aug 1996 17:32:54 GMT
Organization: Massachvsetts Institvte of Technology
I am trying to use expect to spawn the kermit program. It then
is supposed to dial the modem and procede.
When I run kermit from the shell, it has no problem dialing the
modem. However, when kermit is spawned by expect, it will not dial.
I thought perhaps the input stream was too fast for kermit and tried
send -s. I do see a long delay before the dial message is sent, but it
still won't dial. Also, I would expect (no pun) that I would see the
characters sent as follows:
atdt ...
But instead I see:
atdt ...
What am I doing wrong?
Thanks for you help.
John Carney
jcarney@garcon.mit.edu
The send command doesn't wait for responses. The echoing you see
is from an expect command running after send has run. At that point,
all the characters have been echoed already - thus, you see the long
pause (while send is running) and the rush of characters (while expect
is running).
Before you ask, no, it doesn't make sense to have send pause
briefly and wait for echoing. Sometimes there is no echoing. And
sometimes things aren't echoed in an intuitive way. So how could send
possibly know what to wait for and how long?
The solution is to use the expect background command:
expect_background -re .+
Just put this after your spawn command and before you start sending
things.
Don
======================================================================
#41. 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.
Tod Olson sent in the following
example of how to use sessreg. He says: sessreg works nicely. Here
is a fragment showing how we invoke sessreg on our Linux machines.
Note: sessreg must be able to write utmp. We decided to make utmp
work writable, since it's a kinda bogus creature anyhow, rather than
make sessreg suid root (or whatever).
...
spawn $shell
expect $prompt
send "sessreg -w /var/run/utmp -a $user\r"
expect $prompt
======================================================================
#42. 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
======================================================================
#43. 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
======================================================================
#44. 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
======================================================================
#45. 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
create their own.
Don
======================================================================
#46. Can't you make tkterm understand any terminal type?
From: swig@teleport.com (Scott Swigart)
Newsgroups: comp.lang.tcl
Date: Tue, 13 Aug 1996 18:50:22 GMT
I looked at tkterm, and it is promising, but it's missing some
critical features. For one, I need something that understands various
terminal types, and can get it's escape sequences from something like
termcap or terminfo, instead of having them hard coded. Also, I
question the ability of an Expect script to keep up if it had 50 or so
types of escape sequences to parse. Actual C code would probably have
to be created to do the parsing, and if you're going to go that far,
why not just create a terminal widget so you could do something like:
terminal .myterm -type vt220
which is more along the lines of what I was originally looking for.
Yes, that would be divine. But terminal emulators are horribly
complex and very little of that complexity can be discerned from the
termcap file. For example, compare xterm's human-readable docs (63k
man page + 18k appendix) to its termcap entry (654 bytes). Now
consider the other hundreds of terminals in termcap each with their
own weird extensions. I can't imagine what kind of ".myterm configure"
interface you'd present to the user. What would you allow the user to
change? The nice thing about tkterm is that everything is accessible
to the user, but I can't imagine doing that through a widget
interface.
Unfortunately, like everyone else, I don't have the time...
Me neither. Call me lazy.
As an aside, I wonder why you want the ability for a terminal emulator
to read termcap/info. Turns out that it's useless (unless what you
are doing is testing termcap itself). Because if your app is using
termcap in the first place, then it doesn't care what terminal type
you choose - so why not choose the one that tkterm does? (And if your
app isn't using termcap, then you have the converse problem.)
Actually, I and several other people did a fair amount of
experimentation (i.e., wrote a lot of C code) to do a universal
terminal emulator - turns out that it's not possible in a general
sense. To support any terminal type, you are going to be forced to go
beyond what termcap/info offers. I.e., you'll have to handedit the
definition or add new ones and/or accept certain limitations.
After many revisions, Software - Practice & Experience is
publishing a paper on tkterm. The paper includes more insights on the
difficulties I've mentioned here. You can get a draft of the paper
at: http://www.cme.nist.gov/msid/pubs/libes96d.ps
Don
======================================================================
#47. Trapping SIGCHLD causes looping sometimes
From: Bryan Kramer
Sender: kramer@hydro.on.ca
Cc: libes@NIST.GOV
Subject: Problem with trap in expect on Solaris
Date: Tue, 17 Sep 1996 11:09:50 -0400
I'm getting an infinite loop running the attached script foo.tcl on my
solaris machine (Ultra Sparc, SunOS 5.5). This does not happen when I
run the version of the same expect that I compiled on a Sparc 20 with
SunOS 4.1.3UI (even though I am running it on the Solaris 5.5. ultra).
trap {
if {[catch {
puts stderr "CALL TRAP [trap -number] [trap -name]"
wait -i 1
} output]} {
puts stderr "TRAP $output"
return
}
puts "TRAP DONE"
} SIGCHLD
if {[catch {exec trivial} msg]} {
puts stderr "Error $msg"
}
Please let me know if there is an immediate work around.
Thanks
--
|Bryan M. Kramer, Ph.D. 416-592-8865, fax 416-592-8802|
|Ontario Hydro, 700 University Avenue, H12-C1 |
|Toronto, Ontario, Canada M5G 1X6 |
B. Kramer Home Page
I haven't analyzed your script in depth, but this sounds like a
problem I've seen before - it's due to an implementation deficiency in
Tcl. The problem is that when an exec'd process finishes, it raises
SIGCHLD. Expect's "wait" sees that it is Tcl's process.
Unfortunately, there is no way to wait for one of Tcl's processes and
tell Tcl that you've done so, nor is there any way to have Tcl wait
itself. So Expect's wait just returns. On some systems alas, this
just causes SIGCHLD to be reraised.
The solution is multipart:
1 Tell John he needs to fix this problem. (I've told him this but he
didn't agree with me that it's a problem.) Tcl needs to provide a new
interface - either to clean up its process or to allow extensions to
do the wait and pass the status back to Tcl so that it can have it
later when needed.
2 Don't call exec while you are trapping SIGCHLD. Since this is a
severe limitation, I recommend you avoid the problem by using
"expect_before eof" to effectively trap the same event. If you're not
already using expect, well, call it every so often anyway.
Don
======================================================================
#48. Why do I get "invalid spawn id"?
Subject: Why do I get "invalid spawn id"
In article <53ggqe$hag@hole.sdsu.edu> khumbert@mail.sdsu.edu writes:
I am trying to write a general looping procedure that will handle
many cases that have similar prompt sequences. The function and one
call are below.
The problem is that when the "looping" function is called I get an
"invalid spawn id(5) while executing "expect $exp1 {send -s "$send1}
timeout {continue}". I only have one spawn in the entire program
(a telnet session). I've tried setting a spawn_id variable for the
telnet spawn and then setting spawn_id to that variable in "looping",
but no dice, same error.
Any ideas? Thanks in advance for any suggestions!!!
Kelly Humbert
proc looping {exp1 exp2 send1 send2} {
global max_tries ### 5 ###
set tries 0
set connected 0
set timeout 60
while {$tries <= $max_tries && $connected == 0} {
incr tries
expect {
$exp1 {send -s $send1}
timeout {continue}
}
expect {
">? " {send -s "\n"}
timeout {continue}
}
expect {
$exp2 {incr connected;send -s $send2}
timeout {continue}
}
}
return $tries
};
What's going on is that the spawned process has closed the
connection. When Expect detects this, it matches the "eof" pattern,
and the spawn id is marked "invalid". However, you aren't testing for
"eof", so the next command in your script finds the invalid spawn id,
hence the complaint.
If you want to find out where the eof is occurring, enable Expect's
diagnostic mode - Expect will get very chatty about what it is doing
internally.
You can handle eof in all your expect statements by add a single
expect_before/after command to your script.
Don
======================================================================
#49. Could you put a version number in the filename of the Expect archive?
From: "Nelson H. F. Beebe"
Date: Mon, 23 Dec 1996 08:46:57 -0700 (MST)
It would be helpful for the expect distribution to contain its version
number, e.g. expect-5.21.6.tar.gz; I had an earlier version called
5.21, and it took some diffing to verify that the expect.tar.gz I
fetched from ftp://ftp.cme.nist.gov/pub/subject/expect/expect.tar.gz
really was newer.
I don't name the file with a version number because I make new
distributions so frequently. I realize that many other distributions
include version numbers in them, but constantly changing filenames
really annoys the heck out of people. I've been packaging Expect this
way for five years and I've only gotten this question twice before.
In contrast, I'm responsible for a number of other files on our ftp
server that do occasionally change names, and I get no end of
questions from people about where such and such a file has gone or why
their ftp request fails.
So that people don't have to download the distribution only to find
it hasn't changed, there is a HISTORY file in the distribution
directory. It's relatively short and has the latest version number at
the top (with any changes listed immediately after).
Don
======================================================================
#50. Why does Expect work as root, but say "out of ptys" when run as myself?
Expect works fine as root, but when I run it as myself it says "out of
ptys" (which I know isn't true). Any ideas?
Sounds like a misconfiguration problem on your system. For
example, once I saw this on a Digital system where the system
administrator had decided to remove setuid from all programs ("I heard
that setuid is a security risk, right?"). On that particular system,
Expect uses a system library function that internally calls an
external program chgpt which exists solely for the purpose of managing
ptys. Needless to say, it must be setuid. Unfortunately, the library
function doesn't do enough error checking, and there's no way for Expect
to know that, so there's nothing I can do to give a better diagnostic
explaining how your system is misconfigured.
Don
======================================================================
#51. Why does spawn fail with "sync byte ...."?
When I spawned a process using Expect, I got the following
message:
parent: sync byte read: bad file number
child: sync byte write: bad file number
This is one of these "should not happen" errors. For example, the
following question in this FAQ mentions that it could be the fault of
the C library. Another possibility is that you've run out of some
system resource (file descriptors). The most likely reason is that
you're calling spawn in a loop and have neglected to call close and
wait.
Don
======================================================================
#52. Why does Expect fail on RedHat 5.0?
Lots of people have reported the following error from Expect on
RedHat 5.0:
failed to get controlling terminal using TIOCSCTTY
parent sync byte write: broken pipe
Martin Bly reports that:
The fault is/was in the GNU libc (aka glibc) provided by Red Hat
Software. Our sysadmin updated the version of the C libraries we have
installed and both problems have vanished - in the case of the expect
test, without a rebuild.
======================================================================
#53. Why does Expect fail on RedHat 5.1?
People have reported the following error from Expect on RedHat
5.1:
failed to get controlling terminal using TIOCSCTTY
parent sync byte write: broken pipe
If there are any people
who have some debugging experience and can reproduce that error on
RedHat 5.1, read on:
First look in the man page (or perhaps diff the 5.1 and pre-5.1 man
pages) governing TIOCSTTY and let me know what you find.
Alternatively look at the source to xterm (or some other program that
must allocate a pty) and see how it is allocating a pty.
If anyone else is wondering if the problem has been fixed by the time
you read this, just check the FAQ again. I'll update it as soon as
the problem has been successfully diagnosed.
Don
======================================================================
#54. Is Expect Y2K compliant?
The short answer is: Yes, if you're using a modern version of Tcl
(7.6p2 or later).
Longer answer: Tcl 7.5 and 7.6p0/1 had bugs that caused them to be
noncompliant with regard to how POSIX defines 2-character years. If
your scripts use 2-character years, you should upgrade to a modern
version of Tcl. If your scripts use 4-character years, than you have
nothing to worry about.
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: Tue Sep 22 17:52:23 EDT 1998 by Don Libes