Analysing a shell script

Question

This would be part of a reverse-engineering project.

To determine and document what a shell script (ksh, bash, sh) does, it is comfortable, if you have information about what other programs/scripts it calls.

How could one automate this task? Do you know any program or framework that can parse a shell script? This way for instance, I could recognize external command calls -- a step to the right direction.

Answer 1

For bash/sh/ksh, I think you can easily modify their source to log what has been executed. That would be a solution.

Answer 2

strace is your friend.

Answer 3

bash -v script.sh ?

Answer 4

Bash's xtrace is your friend.

You can invoke it with:

• set -x at the top of your script,
• by calling your script with bash -x (or even bash --debugger -x),
• or recursively by doing (set -x; export SHELLOPTS; your-script; )

Answer 5

If you can't actually run the script, try loading it into a text editor that supports syntax highlighting for Bash. It will color-code all of the text and should help indicate what is a reserved word, variable, external command, etc.

Answer 6

How about: 1. Get a list of distinct words in that script 2. Search $PATH to find a hit for each ?