Check if a Bash array contains a value

arrays bash
Paolo Tedesco picture Paolo Tedesco · Sep 10, 2010 · Viewed 577.3k times · Source

In Bash, what is the simplest way to test if an array contains a certain value?

Answer

Keegan picture Keegan · Mar 13, 2013

This approach has the advantage of not needing to loop over all the elements (at least not explicitly). But since array_to_string_internal() in array.c still loops over array elements and concatenates them into a string, it's probably not more efficient than the looping solutions proposed, but it's more readable.

if [[ " ${array[@]} " =~ " ${value} " ]]; then
    # whatever you want to do when array contains value
fi

if [[ ! " ${array[@]} " =~ " ${value} " ]]; then
    # whatever you want to do when array doesn't contain value
fi

Note that in cases where the value you are searching for is one of the words in an array element with spaces, it will give false positives. For example

array=("Jack Brown")
value="Jack"

The regex will see "Jack" as being in the array even though it isn't. So you'll have to change IFS and the separator characters on your regex if you want still to use this solution, like this

IFS=$'\t'
array=("Jack Brown\tJack Smith")
unset IFS
value="Jack"

if [[ "\t${array[@]}\t" =~ "\t${value}\t" ]]; then
    echo "true"
else
    echo "false"
fi

This will print "false".

Obviously this can also be used as a test statement, allowing it to be expressed as a one-liner

[[ " ${array[@]} " =~ " ${value} " ]] && echo "true" || echo "false"

Related questions

Loop through an array of strings in Bash?

I want to write a script that loops through 15 strings (array possibly?) Is that possible? Something like: for databaseName in listOfNames then # Do something end

Read More
Split string into an array in Bash

In a Bash script I would like to split a line into pieces and store them in an array. The line: Paris, France, Europe I would like to have them in an array like this: array[0] = Paris array[1] = France array[2] = …

Read More
Add a new element to an array without specifying the index in Bash

Is there a way to do something like PHPs $array[] = 'foo'; in bash vs doing: array[0]='foo' array[1]='bar'

Read More