Exploring Expect by Libes, Don -- Read -- Imperial Library of Trantor

Index

Exploring Expect Dedication A Note Regarding Supplemental Files Preface

Expect—Why another tool? Tcl—A Little History Acknowledgments We’d Like to Hear From You

How To Read This Book

Notational Conventions Exercises

1. Intro—What Is Expect?

Ouch, Those Programs Are Painful! A Very Brief Overview A First Script—dialback Total Automation

Testing

Differing Behavior When Running Non-Interactively Partial Automation Dangerous, Unfriendly, Or Otherwise Unlikable User Interfaces Graphical Applications A Little More About Tcl Job Control Background Processes Using Expect With Other Programs Using Expect On UNIX Using Expect On Other Operating Systems Using Expect In Real Applications Using Expect In Commercial Applications—Legalese Obtaining Expect and the Examples Expect And Tcl Resources

Important Reading Material Other Books Other Online Documentation Support

Exercises

2. Tcl—Introduction And Overview

Everything Is A String Quoting Conventions

Return Values Puts

Expressions Braces—Deferring Evaluation Control Structures

The while Command The incr Command The for Command The if Command The switch Command Continuation Lines The break And continue Commands The proc And return Commands The source Command

More On Expressions Lists

Selecting Elements Of Lists Varying Argument Lists Lists Of Lists Creating Lists The list And concat Commands Building Up Lists With The lappend Command The linsert Command The lreplace Command The lsearch Command The lsort Command The split And join Commands

More Ways To Manipulate Strings

The scan And format Commands The string Command The append Command

Arrays Indirect References

Variable Information Array Information Unsetting Variables Tracing Variables

Handling Errors

Causing Errors

Evaluating Lists As Commands Passing By Reference

Evaluating Commands In Other Scopes

Working With Files File I/O

File Name Matching Setting And Getting The Current Directory File Name Manipulation File Information

Executing UNIX Commands Environment Variables Handling Unknown Commands Libraries Is There More To Tcl? Exercises

3. Getting Started With Expect

The send Command The expect Command Anchoring What Happens When Input Does Not Match Pattern-Action Pairs Example—Timed Reads In The Shell The spawn Command The interact Command Example—Anonymous ftp Exercises

4. Glob Patterns And Other Basics

The * Wildcard

* At The Beginning Of A Pattern Is Rarely Useful * At The End Of A Pattern Can Be Tricky

More Glob Patterns Backslashes Handling Timeout Handling End Of File (eof) Hints On The spawn Command Back To Eof The close Command Programs That Ignore Eof The wait Command Exercises

5. Regular Expressions

Regular Expressions—A Quick Start Identifying Regular Expressions And Glob Patterns Using Parentheses To Override Precedence Using Parentheses For Feedback More On The timed–read Script Pattern Matching Strategy Nested Parentheses Always Count Parentheses Even Inside Of Alternatives Example—The Return Value From A Remote Shell Matching Customized Prompts Example—A Smart Remote Login Script What Else Gets Stored In expect_out More On Anchoring Exercises

6. Patterns, Actions, And Limits

Matching Anything But Really Complex Patterns Really Simple Patterns Matching One Line And Only One Line Tcl’s string match Command Tcl’s regexp Command Tcl’s regsub Command Ignoring Case All Those Other String Functions Are Handy, Too Actions That Affect Control Flow Example—rogue Character Graphics More Actions That Affect Control Flow Matching Multiple Times Recognizing Prompts (Yet Again) Speed Is On Your Side Controlling The Limits Of Pattern Matching Input The full_buffer Keyword Double Buffering Perpetual Buffering The Politics Of Patterns Expecting A Null Character Parity Length Limits Comments In expect Commands Restrictions On expect Arguments eval—Good, Bad, And Ugly Exercises

7. Debugging Patterns And Controlling Output

Pattern Debugging Enabling Internal Diagnostics Logging Internal Diagnostics Disabling Normal Program Output The log_user Command Example—su2 Recording All Expect Output Sending Messages To The Log About File Names Log And Diagnostic State Exercises

8. Handling A Process And A User

The send_user Command The send_error Command The expect_user Command Dealing With Programs That Reprompt Dealing With Programs That Miss Input Sleeping Line Versus Character-Oriented And Other Terminal Modes Echoing Prompting For A Password On Behalf Of A Program Security And Insecurity

Securing Scripts By File Protection Securing Scripts By Host Protection

Resetting The Terminal Upon Exit More On The stty Command The system Command Redirecting The Standard Input Or Output The expect_tty Command The send_tty Command Exercises

9. The Expect Program

Expect—Just Another Program Invoking Scripts Without Saying “expect” Rewriting The #! Line The .exp Extension The—And Other Flags The —c Flag The -f Flag Writing The #! Line The −i Flag The -n And -N Flags The -d Flag The -D Flag The -b Flag The - Flag The interpreter Command

The Terminal Mode During The interpreter Command The interpreter Prompt Changing The Prompt—prompt1 And prompt2 Causing The interpreter Command To Return ^D Using interpreter In Production Scripts

Exercises

10. Handling Multiple Processes

The spawn_id Variable Example—chess Versus chess Example—Automating The write Command How exp_continue Affects spawn_id The Value Of spawn_id Affects Many Commands Symbolic Spawn Ids Job Control Procedures Introduce New Scopes How Expect Writes Variables In Different Scopes Predefined Spawn Ids Exercises

11. Handling Multiple Processes Simultaneously

Implicit Versus Explicit Spawn Ids Waiting From Multiple Processes Simultaneously Example—Answerback Which Pattern Goes With Which Spawn Id Which Spawn Id Matched Spawn Id Lists Example—Connecting Together Two Users To An Application Example—Timing All Commands Matching Any Spawn Id Already Listed The expect_before And expect_after Commands

How Long Are expect_before And expect_after In Effect? Using expect_before And expect_after With The Currently Spawned Process—DANGER Undoing The Effects Of expect_before And expect_after Information On The Current expect_before And expect_after Patterns expect_before And expect_after Actions

Indirect Spawn Ids

Indirect Spawn Ids—Are They Really That Useful?

Exercises

12. Send

Implicit Versus Explicit Spawn Ids Sending To Multiple Processes Sending Without Echoing Sending To Programs In Cooked Mode Sending Slowly Sending Humanly Sending Nulls Sending Breaks Sending Strings That Look Like Flags Sending Character Graphics Comparing send To puts Exercises

13. Spawn

The Search Path Philosophy--Processes Are Smart Treating Files As Spawned Processes Opening Ttys Bugs And Workarounds Process Pipelines And Ptys Automating xterm Checking For Errors From spawn spawn -noecho Example—unbuffer Obtaining Console Output Setting Pty Modes From spawn Hung Ptys Restrictions On Spawning Multiple Processes Getting The Process Id From A Spawn Id Using File I/O Commands On Spawned Processes Exercises

14. Signals

Signals Signals In Spawned Processes Notes On Specific Signals

SIGINT—Software Interrupt Signal SIGTERM—Software Termination Signal SIGQUIT—Quit Signal SIGKILL—Kill Signal SIGCHLD—Child Termination Signal SIGHUP—Hangup Signal SIGPIPE—Broken Pipe Signal SIGWINCH—Window Size Change Signal SIGTSTP—Terminal-Generated Stop SignalSIGSTOP—Kernel-Generated Stop SignalSIGCONT—Continue Signal SIGUSR1 And SIGUSR2—User-Defined Signals Other Signals

When And Where Signals Are Evaluated

Avoiding Problems Caused By Signal Handlers

Overriding The Original Return Value Using A Different Interpreter To Process Signals Exit Handling Exercises

15. Interact

The interact Command Simple Patterns Exact Matching Matching Patterns From The Spawned Process Regular Expressions What Happens To Things That Do Not Match More Detail On Matching Echoing Avoiding Echoing Giving Feedback Without -echo Telling The User About New Features Sending Characters While Pattern Matching The continue And break Actions The return Action The Default Action Detecting End-Of-File Matching A Null Character Timing Out More On Terminal Modes (Or The -reset Flag) Example—Preventing Bad Commands Exercises

16. Interacting With Multiple Processes

Connecting To A Process Other Than The Currently Spawned Process Connecting To A Process Instead Of The User Example—rz And sz Over rlogin Redirecting Input And Output Default Input And Output Controlling Multiple Processes—kibitz

How kibitz Works

Combining Spawn Ids In A Single -input Or -output Which Spawn Id Matched Indirect Spawn Ids An Extended Example—xkibitz Exercises

17. Background Processing

Putting Expect In The Background Running Expect Without A Controlling Terminal Disconnecting The Controlling Terminal The fork Command The disconnect Command Reconnecting Using kibitz From Other Expect Scripts Mailing From Expect A Manager For Disconnected Processes—dislocate Expect As A Daemon Example—Automating Gopher and Mosaic telnet Connections

Telling The System About Your Daemon

Exercises

18. Debugging Scripts

Tracing Logging Command Tracing Variable Tracing Example—Logging By Tracing UNIX System Call Tracing Tk And tkinspect Traditional Debugging Debugger Command Overview And Philosophy Stepping Over Procedure Calls Stepping Into Procedure Calls Where Am I The Current Scope Moving Up And Down The Stack Returning From A Procedure Continuing Execution Defining Breakpoints

Breakpoint By Line Number And Filename Breakpoint By Expression Breakpoint By Pattern Match Breakpoint Actions Limitations Of Breakpoint Actions And Interactive Commands General Form Of Breakpoints Listing Breakpoints Deleting Breakpoints

Help Changing Program Behavior Changing Debugger Behavior Exercises

19. Expect + Tk = Expectk

Tk—A Brief Technical Overview

Widgets Other Widgets And Naming Conventions Displaying Widgets Bindings And Events The Event Loop

Expectk

Expectk Scripts

The send Command An Extended Example—tkpasswd The expect Command And The Tk Event Loop The expect_background Command Multiple Spawn Ids In expect_background Background Actions Example—A Dumb Terminal Emulator Example—A Smarter Terminal Emulator Using The Terminal Emulator For Testing And Automation

The term_expect Procedure

Exercises

20. Extended Examples

Encrypting A Directory File Transfer Over telnet You Have Unread News—tknewsbiff

The tknewsbiff Script

Exercises

21. Expect, C, And C++

Overview Linking Include Files Ptys And Processes Allocating Your Own Pty Closing The Connection To The Spawned Process Expect Commands Regular Expression Patterns

Caching Regular Expressions

Exact Matching Matching A Null What Characters Matched When The Number Of Patterns Is Not Known In Advance Expecting From Streams Running In The Background Handling Multiple Inputs And More On Timeouts Output And Debugging Miscellany Pty Trapping Exercises

22. Expect As Just Another Tcl Extension

Adding Expect To Another Tcl-based Program Differences Between Expect And The Expect Extension In Another Program Adding Extensions To Expect Adding Extensions To Expectk Creating Script-less Expect Programs Functions And Variables In The Expect Extension

Shared Variables Non-Shared Variables and Functions

Exercises

23. Miscellaneous

Random Numbers Example—Generating Random Passwords The Expect Library Expect Versions Timestamps The time Command Exercises

A. Appendix—Commands and Variables

Commands And Flags Variables

Index About the Author Copyright

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