This question bad substitution shell- trying to use variable as name of array does something similar to what I need but for arrays. I'm very new to bash scripting and what I need is to do something like this:
# input
humantocheck="human1"
declare -A human1
declare -A human2
human1=( ["records_file"]="xxxxx.txt")
human2=( ["records_file"]="yyyyy.txt")
echo ${$humantocheck[records_file]}
With expected output of:
xxxxx.txt
However I get a bad substitution error when I try this.
This is exactly the scenario that the bash 4.3 feature namevars (borrowed from ksh93) is intended to address. Namevars allow assignment, as opposed to lookup alone, and are thus more flexible than the ${!foo} syntax.
# input
humantocheck="human1"
declare -A human1=( ["records_file"]="xxxxx.txt" )
declare -A human2=( ["records_file"]="yyyyy.txt" )
declare -n human=$humantocheck # make human an alias for, in this case, human1
echo "${human[records_file]}" # use that alias
unset -n human # discard that alias
See BashFAQ #6 for a comprehensive discussion of both associative arrays and indirect expansion in general.
One way to do this with an indirect reference is:
ref=$humantocheck[records_file]
echo ${!ref}
Bash: Indirect Expansion Exploration is an excellent reference for indirect access to variables in Bash.
Note that the echo command, which was intended to be a minimal modification to the original code, is unsafe in several ways. A safe alternative is:
printf '%s\n' "${!ref}"
ref="$humantocheck[records_file]" with double quotes to prevent mischief. The key can also be in a variable, of course: ref="$humantocheck[$key]".
human_file=$humantocheck[human_name] at the top of my file and use ${!human_file} as a sort of template variable for all other commands throughout the file! Really cool.
ref=$humantocheck[$key] is no less safe than ref="$humantocheck[$key]".deps_file=$app_type[deps_file] and if [ -n ${!deps_file+1} ]; then echo Not set...; else echo key is set...; fi isn't working for meif [ -n "${!deps_file+1}" ]; then echo 'Key is set' ; else echo 'Key is not set' ; fi. It's better to use [[...]] instead of [...] in Bash code because, among other advantages, you mostly don't have to worry about quotes.
humantocheckis not an array. If anything is going to work, it'll be a variation on${${!humantocheck}[records_file]}but I'm not confident (I didn't find the magic combo). (See shell parameter expansion.)humanfrom eitherhuman1orhuman2and then reference that. Unfortunately, I don't think there's a way to assign whole associative arrays in one swell foop. The best I've come up with uses a loop to copy the associative array element by element:for key in "${!human1[@]}"; do human[$key]="${human1[$key]}"; done. Generally speaking, using indirect variable names leads to complications, and a rethink/rewrite.