Expect

Tool for Automation and Testing

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.

Expect – TCL* Basics

Everything is a command No Fixed Parser Case-Sensitive Explicit Expression Evaluation

– set a 5 a = 5– set b a+2 b = a+2– set c [expr $a+2] 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

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

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, AT&T, 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.

Expect – “Hello World!”

Start Expect with “expect” or write the script to a file and run > expect filename

send “Hello World!\n” expect “Hi\n”Putting it together Expect “Hi\n” { send “Hi World!\n” }

Expect – More Advanced

expect "hi\n" { send "Hi World!\n" } \

"hello\n" {send "Hello World!\n" } \

"bye\n" {send "Bye World!\n" }

Expect - Automation

spawn ftp $argvexpect "Name" { send "anonymous\r" } \ "name" { send "anonymous\r" }expect "assword:"send "nobody@nobody.com\r"interact

Expect - Others

Brute Force security Beer Chess Weather Rogue Hunt

Expect - GnuChess

# start things rollingspawn gnuchessset id1 $spawn_idexpect "White \\(1\\) :"send "random\r"send "depth 6\r"send "go\r"# read_first_moveexpect -re "My move is : (.*)\n"

spawn gnuchessset id2 $spawn_idexpect "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) } }}

Expect - Questions