Or just don't use Bash. Python is a great scripting language, and won't blow your foot off if you try to iterate through an array.

Other than that, yeah, if you must use bash, set -eu -o pipefail; the IFS is new and mildly interesting idea to me.

> The idea is that if a reference is made at runtime to an undefined variable, bash has a syntax for declaring a default value, using the ":-" operator:

Just note that defaulting an undefined variable to a value (let's use a default value of "fallback") for these examples is,

  ${foo-fallback}

The syntax,

  ${foo:-fallback}

means "use 'fallback' if foo is unset or is equal to "". (The :, specifically triggers this; there's a bunch of others, like +, which is "use alternate value", or, you'll get the value if the parameter is defined, nothing otherwise.

  if [[ "${foo+set}" == "set" ]]; then
    # foo is not undefined.
  fi

And similarly,

  ${foo:+triggered}

will emit triggered if foo is set and not empty.)

See "Parameter Expansion" in the manual. I hate this syntax, but it is the syntax one must use to check for undefined-ness.