Bash - check if string is empty

In this article, we would like to show you how to check if string is empty in Bash.

In this example, we use -z operator to check if string length is zero inside the if statement.

script.sh file:

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#!/bin/bash

​

string=""

​

if [ -z "$string" ]; then

    echo "The string is empty"

fi

Note: this approach should be used in POSIX shells where other solutions may not work.

Run in command line:

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./script.sh

Output:

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The string length is empty

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#!/bin/bash

​

string=""

​

if test -z "$string"; then

    echo "The string is empty"

fi

Note: [ ] notation is shorthand of test command.

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#!/bin/bash

​

string=""

​

if [[ -z "$number" ]]; then

    echo "The string is empty"

fi

Note: [[ ]] notation is like extended test command, adding additional features (e.g. regular expressions).

1. Bash - check if string is not empty