Running Multiple expect/TCL Scripts in a Single Shell Script

Pubblicato il: 18 marzo 2025
sul canale di: vlogize
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Discover how to effectively run multiple `expect/TCL` scripts within the same shell script while executing shell commands seamlessly in between.
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This video is based on the question https://stackoverflow.com/q/75292320/ asked by the user 'monk' ( https://stackoverflow.com/u/5584716/ ) and on the answer https://stackoverflow.com/a/75294757/ provided by the user 'Colin Macleod' ( https://stackoverflow.com/u/107626/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Running Multiple expect/TCL Scripts in a Single Shell Script: A Comprehensive Guide

When managing remote systems or automating tasks in Unix-like environments, you may find yourself needing to run chunks of expect/TCL scripts along with shell commands within a single shell script. This article will guide you through the process of achieving that.

The Challenge

Imagine you have a requirement to establish an SSH connection to a remote server and run a series of commands. You may also want to execute shell commands in between these expect scripts. Here's a high-level view of the challenge:

Run the first chunk of expect to SSH into a remote server.

Execute some shell commands.

Run additional expect scripts for further commands on that remote server.

The initial attempt may lead you to believe that executing multiple expect blocks seamlessly is impossible due to limitations in managing child process objects.

Solution Breakdown

Let’s explore the solution step-by-step to make this task manageable and straightforward.

Step 1: Establish SSH Connection with Expect

Instead of using multiple shells, we can use expect to handle the SSH connection directly.

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Step 2: Running Shell Commands

Once you are connected to the remote server, you can execute shell commands using the puts command with exec. This allows you to capture the output of your shell commands directly in Expect/Tcl.

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Step 3: Further Commands Using Expect

After executing the shell commands, you can continue to send additional commands over the established SSH session and manage their responses.

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Complete Script Example

Putting it all together, the final script seamlessly integrates the SSH connection and other commands in a structured manner. Here’s the complete example:

[[See Video to Reveal this Text or Code Snippet]]

Summary

By following the steps outlined above, running multiple expect/TCL scripts within the same shell script becomes a manageable and efficient process. The key takeaway is using Expect to handle the SSH session directly rather than spawning multiple instances, which complicates interaction with the spawned bash shell.

This approach not only solves the initial problem but also allows you to dynamically run commands received from other programs, adapting your expect script flexibly as needed.

Now, you can effectively handle complex automation tasks without the hassle of redundant bash sessions!


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