How to 'set -x' for scripts other than my own

Question

I am still dealing with a bug from another question which has gone unanswered because I can't get debugging information.

I have scripts running other scripts and I need to see how the tty is getting disconnected from the terminal.

Is there any way to 'set -x' globally? I can't set it in the problem script because it is dynamically generated, not by me, but I'd like to see what's wrong with it.

Answer 1

Invoke Bash with a shell option set

According to the Invoking Bash section of the Bash manual,

All of the single-character options used with the set builtin (see The Set Builtin) can be used as options when the shell is invoked

This means you can run a Bash script with the xtrace option set by directly invoking bash with the -x option and the file name of the script as an argument, e.g.,

bash -x /path/to/script

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Configure shell option for all shell scripts

When you say “global”, I presume you want it set the xtrace option for all non-interactive invocations of Bash. To do this, set the BASH_ENV environment variable to a suitable filename and then create that file with set -x as its contents:

export BASH_ENV=~/.bash_env
echo set -x > ~/.bash_env

From the man page:

When bash is started non-interactively, to run a shell script, for example, it looks for the variable BASH_ENV in the environment, expands its value if it appears there, and uses the expanded value as the name of a file to read and execute.