The BASH Debugger Project contains the most comprehensive source-code debugger
for bash that has been written. It has a similar command interface as gdb.

The purpose of the BASH debugger is to help you catch bugs in the act:

    * Start your script, specifying anything that might affect its behavior.
    * Make your script stop on specified conditions.
    * Examine what has happened when your script has stopped.
    * Change things in your script, so you can experiment with correcting the
      effects of one bug and go on to learn about another. 

Read the INSTALL file in the source directory for instructions if you wish to
enable readarray support. readarray speeds up initial loading of large scripts.