Question
How to check if a variable is empty in a bash script?
- Posted on November 24, 2020
- Linux BasicsLinux CommandsUbuntuCentOS
Asked by Bobby Iliev
I recently got asked how to check if a variable is empty in a Bash script.
Here is an example script, where we expect the user to enter a value when asked to do so:
#!/bin/bash
echo "Enter your name: "
read name
echo "Hello ${name}"
If you run the script, you will be able to press enter, and the output would be just Hello.
Here’s how to check if a variable is empty in a Bash script!
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The quick answer on how to check if a variable is empty in Bash is to use the following expression:
[[ -z ${string} ]]
If we take the example from above, you can then use this in an if statement as follows:
#!/bin/bash
echo "Enter your name: "
read name
if [[ -z ${name} ]] ; then
echo "Make sure to specify your name!"
else
echo "Hello ${name}"
fi
You can also combine this in a while statement and ask the user for their input until they actually provide a value:
#!/bin/bash
echo "Enter your name: "
read name
while [[ -z ${name} ]] ; do
echo "Make sure to specify your name!"
echo "Enter your name: "
read name
done
echo "Hello ${name}"
That way, your user will be asked to enter their name until they actually input some value.
I hope that this helps! Regards, Bobby
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