Here we have a debugger (the debugger?) for Bash 3.0 and higher.

The command syntax generally follows that of the
zsh debugger trepanning debuggers
and, more generally, GNU debugger gdb.

There are 3 ways to get into the debugger. If bash (with debugger
support enabled which is the default) is installed and the debugger
are both installed properly. Then:

   bash --debugger -- bash-script-name script-arg1 script-arg2...

If bash isn't installed in a way that will find bashdb, then:

   bashdb [bashdb-opts] -- bash-script-name script-arg1 script-arg2...

The downside here is that $0 will be "bashdb" not
bash-script-name. Also call stack will show the invocation to bashdb.

Finally, to invoke the debugger from the script

  # my script
  # work, work, work, ...

  # Load debugger support
  source <bashdb-installation>/bashdb-trace -L <bashdb-installation>
  # work, work, work or not...
  _Dbg_debugger; :   # Calls the debugger at the line below
  stop_here

An advantage of the above is that there is no overhead up until you
invoke the debugger. Typically for large bash programs like
configuration scripts, this is a big win.

IMPORTANT NOTE IF YOU USE THE ABOVE TO DEBUG CONFIGURE SCRIPTS...

stdin is closed by configure early on. This causes the debugger to quit.
You can get around this invoking a command script that sets debugger
up input and output. Run tty to figure out what the terminal tty is set to.

  $ tty
  /dev/pts/3
  $

Above it came out to /dev/pts/3. Let's go with that. Put the folliwng
in a file say /tmp/bashdb-configure

  source /dev/pts/3
  tty /dev/pts/3

Now arrange to read that configuration file using the -x or --eval-command
switch:

  source <bashdb-installation>/bashdb-trace -L <bashdb-installation> -x /tmp/bashdb-configure

• manual page
• tree-structured reference manual
• tree-structured reference manual

See INSTALL for generic GNU configure installation instructions.