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@@ -0,0 +1,1989 @@ +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 <a language I already know>? +#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 <lots of random extensions> 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 <chymes@crew.umich.edu> +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 <a language I already know>? + +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 <joe@ns.via.net> +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 <mrj@CIS.Prime.COM> +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 <charlton@cs.utexas.edu> +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 <wade@cs.ualberta.ca> +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) <william@ritchie.acomp.usf.edu> +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 <claird@Starbase.NeoSoft.COM> +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 <lots of random extensions> together? + +From: libes (Don Libes) +To: Frank Winkler <winkler@eas.iis.fhg.de> +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 <aqu@cisco.com> +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 <wmt@visi.net> +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 <sunanda@simvax.labmed.umn.edu> +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 <khughesDoy1yH.5zo@netcom.com>, Kirby Hughes <khughes@netcom.com> 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: + +a<pause>t<pause>d<pause>t<pause> ... + +But instead I see: + +<long_pause>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) <william@ritchie.acomp.usf.edu> +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 <tao@stone.lib.uchicago.edu> 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 <djamal@lyohp5.in2p3.fr> +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 <bryan.kramer@hydro.on.ca> +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 $msg" +} + + +Please let me know if there is an immediate work around. + +Thanks +-- +|Bryan M. Kramer, Ph.D. 416-592-8865, fax 416-592-8802| +|Ontario Hydro, 700 University Avenue, H12-C1 | +|Toronto, Ontario, Canada M5G 1X6 | +<A href="http://www.cs.toronto.edu/~kramer">B. Kramer Home Page</A> + +I haven't analyzed your script in depth, but this sounds like a +problem I've seen before - it's due to an implementation deficiency in +Tcl. The problem is that when an exec'd process finishes, it raises +SIGCHLD. Expect's "wait" sees that it is Tcl's process. +Unfortunately, there is no way to wait for one of Tcl's processes and +tell Tcl that you've done so, nor is there any way to have Tcl wait +itself. So Expect's wait just returns. On some systems alas, this +just causes SIGCHLD to be reraised. + +The solution is multipart: + 1 Tell John he needs to fix this problem. (I've told him this but he +didn't agree with me that it's a problem.) Tcl needs to provide a new +interface - either to clean up its process or to allow extensions to +do the wait and pass the status back to Tcl so that it can have it +later when needed. + 2 Don't call exec while you are trapping SIGCHLD. Since this is a +severe limitation, I recommend you avoid the problem by using +"expect_before eof" to effectively trap the same event. If you're not +already using expect, well, call it every so often anyway. + +Don + +====================================================================== + +#48. Why do I get "invalid spawn id"? + +Subject: Why do I get "invalid spawn id" +In article <53ggqe$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" <beebe@math.utah.edu> +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 <ussc@star.rl.ac.uk> 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 |