Linux Shell Scripting Cookbook - Third Edition

Automating with expect

expect does not come by default on all Linux distributions. You may have to install the expect package with your package manager (apt-get or yum).

Expect has three main commands:

Commands	Description
spawn	Runs the new target application.
expect	Watches for a pattern to be sent by the target application.
send	Sends a string to the target application.

The following example spawns the backup script and then looks for the patterns *folder* and *file* to determine if the backup script is asking for a folder name or a filename. It will then send the appropriate reply. If the backup script is rewritten to request files first and then folders, this automation script still works.

 #!/usr/bin/expect #Filename: ...