Expect

1
Expect

• Tool for Automation and Testing

2
Expect - Introduction

• Unix automation and testing tool
• Written by Don Libes
• Primarily designed as an extension to the Tcl
  scripting language
• Useable in interactive applications such as
  telnet, ftp, passwd, fsck, rlogin, tip, ssh, and
  others.

3
Expect TCL Basics

• Everything is a command
• No Fixed Parser
• Case-Sensitive
• Explicit Expression Evaluation
• set a 5 ? a 5
• set b a2 ? b a2
• set c expr a2 ? c 7 (Note for variable
  substitution)
• Simple variables are strings of arbitrary length
• Real Int ? cast to real
• Non-numeric string and real/int ? cast to string
• Built in Lists
• Standard flow control structures (while, if,
  etc.)
• String manipulation with Regular Expressions
• Procedures arguments can be passed by value or
  reference
• Tool Command Language

4
Expect The Programming Language

• Extension of TCL, so the syntax is TCL syntax
• Basic command set
• expect
• send
• spawn
• Interact
• Regular Expression pattern
• matching
• Glue to combine separate
• executables

5
Expect Pros / Cons

• Pros
• Built on existing system tools, so learning curve
  is small.
• Extensive support from corporate entities
  Silicon Graphics, IBM, HP, Sun, Xerox, Amdahl,
  Tektronix, ATT, ComputerVision and the World
  Bank
• Numerous ports to other programming languages
  (Perl, Python, java, etc.)
• Cons
• Only useful for command line scripting
• Cryptic syntax for those unfamiliar with TCL
  (When do I use a again?)
• Generally machine dependent tools are run with
  Expect, so porting scripts cross-platform is not
  easily supported.

6
Expect Hello World!

• Start Expect with expect or write the script to
  a file and run gt expect filename
• send Hello World!\n
• expect Hi\n
• Putting it together
• Expect Hi\n
• send Hi World!\n

7
Expect More Advanced

• expect "hi\n" send "Hi World!\n" \
• "hello\n" send "Hello World!\n"
  \
• "bye\n" send "Bye World!\n"

8
Expect - Automation

• spawn ftp argv
• expect "Name" send "anonymous\r" \
• "name" send "anonymous\r"
• expect "assword"
• send "nobody_at_nobody.com\r"
• interact

9
Expect - Others

• Brute Force security
• Beer
• Chess
• Weather
• Rogue
• Hunt

10
Expect - GnuChess

• start things rolling
• spawn gnuchess
• set id1 spawn_id
• expect "White \\(1\\) "
• send "random\r"
• send "depth 6\r"
• send "go\r"
• read_first_move
• expect -re "My move is (.)\n"
• spawn gnuchess
• set id2 spawn_id
• expect "White \\(1\\) "
• send "random\r"
• send "depth 5\r"
• send expect_out(1,string)

• while 1
• expect
• -i id2 -re "is (.)\n"
• send -i id1 expect_out(1,string)
• -i id1 -re "is (.)\n"
• send -i id2 expect_out(1,string)

11
Expect - Questions