Set variable from item in array before the array is looped in a bash script

Question

I am creating an array from the output of a command and then i am looping through the array and running commands that use each item in the array. Before i loop through the array i want to create a variable that uses one of the values in my array. I will use this value when one of the items in the array contains a specific string.

I am not sure how to pick the value i need to set the variable from my array before i then loop through the array. I currently have this which is not working for me. I have also tried looping through to get my value but the value does not follow to the next loop, i dont think its being set and i cant keep the loop open as i am looping inside my loop.

readarray -t ARRAY < <( command that gets array of 5 hostnames )
if [[ $ARRAY[@]  == *"FT-01"* ]]; then
FTP="$ARRAY"
fi

for server in "${ARRAY[@]}"; do

echo "Server: ${srv}"
echo "-------------------"
if [[ $server == *"ER-01"* ]]; then
echo " FTP server is ${FTP} and this is ${server}"
fi
done

I'm pretty sure the first if statement would never work but i am at a loss to how to pick out the the value i need from the array.

I have troubles understanding your question, partly due to formulations like "off the back" and partly because the formulations are very broad (for instance, "the value" – which value exactly?). Also, your script has a loop variable srv but uses $server. Please try to rephrase your question, fix and format your script, and maybe add a concrete example (something like "I have the array ..., because it contains ... I want to do ..."). — Socowi
– Socowi, Commented Oct 30, 2019 at 12:36
Edited to be clearer, i am looking for a value in my array that matches a string and then i am going to set a variable that is that value. — a.smith
– a.smith, Commented Oct 30, 2019 at 12:43

John Kugelman · Accepted Answer · 2019-10-30 12:50:18Z

1

Sometimes difficulty expressing an idea is a sign that you're thinking like a C programmer rather than a shell scripter. Arrays and for loops aren't the most natural idioms in shell scripts. Consider streaming and pipes instead.

Let's say the command that gets hostnames is called list-of-hostnames. If it prints one host name per line you can filter the results with grep.

FTP=$(list-of-hostnames | grep FT-01)

If you really do want to work with an array you could use printf '%s\n' to turn it into a grep-able stream.

FTP=$(printf '%s\n' "${ARRAY[@]}" | grep FT-01)

answered Oct 30, 2019 at 12:50

John Kugelman

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1 Comment

a.smith Over a year ago

Ahh amazing i was so focused on my array i didn't think to just pipe it and pick out my line! thanks this has achieved exactly what i was after

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