Often you may want to use Bash to check if a variable exists in a list.
You can use the following syntax to do so:
[[ " $my_list " =~ " $my_var " ]] && echo 'Exists' || echo 'Does Not Exist'
This particular example will check if the value stored in the variable named $my_var exists in the list named $my_list and return one of the following strings as a result:
- “Exists”
- “Does Not Exist”
The following example shows how to use this syntax in practice.
Example: How to Check if Variable Exists in List in Bash
Suppose we create a variable in Bash named my_var that contains the following value:
- Mavs
Suppose that we would like to check if this variable exist in a list named my_list that contains the names of various basketball teams.
We can use the following syntax to do so:
my_var="Mavs"
my_list="Hawks Nets Mavs Celtics Lakers Kings"
[[ " $my_list " =~ " $my_var " ]] && echo 'Exists' || echo 'Does Not Exist'
The following screenshot shows how to use this syntax in practice:
Notice that this returns “Exist” since the value stored in the my_var variable does indeed exist in the list name my_list.
Suppose that our my_var variable contained the team name “Rockets” instead.
We can use the following syntax to check if this variable exists in the list of team names:
my_var="Rockets"
my_list="Hawks Nets Mavs Celtics Lakers Kings"
[[ " $my_list " =~ " $my_var " ]] && echo 'Exists' || echo 'Does Not Exist'
The following screenshot shows how to use this syntax in practice:
Notice that this returns “Does Not Exist” since the value stored in the my_var variable indeed does not exist in the list name my_list.
Feel free to replace the strings in the echo statements with any strings that you’d like.
Related Tutorials
The following tutorials explain how to perform other common tasks in Bash:
Bash: How to Select Random Element from an Array
Bash: How to Split a String into Multiple Variables
Bash: How to Trim Trailing Whitespace from a Variable
