Bash Quick Start Guide

The declare command

The declare builtin sets or displays variables (including arrays) and functions. It's not usually needed for setting variables, but it's a good way to get an overview of your shell's current running state, providing more information than the set builtin.

Run with only the -p option, declare prints the values of all of the variables in the current shell environment, along with some short option flags that describe their properties:

bash$ declare -p
declare -- BASH="/bin/bash"
declare -r BASHOPTS="cdspell:checkhash:checkjobs:checkwinsize:...
declare -ir BASHPID
declare -A BASH_ALIASES=()
declare -a BASH_ARGC=()
...

If you include the names of any variables after -p, without the dollar sign prefix, Bash will print results ...