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Bash Case Statement
Bash case statements are generally used to simplify complex conditionals when you have multiple different choices. Using the case statement instead of nested if statements will help you make your bash scripts more readable and easier to maintain.
In this tutorial, we will cover the basics of the Bash case statements and show you how to use them in your shell scripts.
Case Statement Syntax
The Bash case statement takes the following form:
case EXPRESSION in PATTERN_1) STATEMENTS ;; PATTERN_2) STATEMENTS ;; PATTERN_N) STATEMENTS ;; *) STATEMENTS ;; esac
- Each case statement starts with the
casekeyword followed by the case expression and the
inkeyword. The statement ends with the
- You can use multiple patterns separated by the
)operator terminates a pattern list.
- A pattern can have special characters.
- A pattern and its associated commands are known as a clause.
- Each clause must be terminated with
- The commands corresponding to the first pattern that matches the expression are executed.
- It is a common practice to use the wildcard asterisk symbol (
*) as a final pattern to define the default case. This pattern will always match.
- If no pattern is matched the return status is zero. Otherwise, the return status is the exit status of the executed commands.
Case Statement Example
Here is an example using the case statement in a bash script that will print the official language of a given country:
#!/bin/bash echo -n "Enter the name of a country: " read COUNTRY echo -n "The official language of $COUNTRY is " case $COUNTRY in Lithuania) echo -n "Lithuanian" ;; Romania | Moldova) echo -n "Romanian" ;; Italy | "San Marino" | Switzerland | "Vatican City") echo -n "Italian" ;; *) echo -n "unknown" ;; esac
Save the custom script as a file and run it from the command line.
The script will ask you to enter a country. For example, if you type “Lithuania” it will match the first pattern and the
echo command in that clause will be executed.
The script will print the following output:
Enter the name of a country: Lithuania The official language of Lithuania is Lithuanian
If you enter a country that doesn’t match any other pattern except the default wildcard asterisk symbol, let’s say Argentina the script will execute the echo command inside the default clause.
Enter the name of a country: Argentina The official language of Argentina is unknown
By now you should have a good understanding of how to write bash case statements. They are often used to pass parameters to a shell script from the command line. For example, the init scripts are using case statements for starting, stopping or restarting services.
If you have any question or feedback, feel free to leave a comment.