> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Command Line Arguments
> Learn to use command-line arguments in shell scripts for flexibility and reusability, eliminating hard-coded values for improved efficiency.
In this lesson, you'll learn how to use command-line arguments in shell scripts to make them more flexible and reusable. Previously, our script was hard-coded with the mission name, which meant that launching a rocket for a different mission required manual edits to the code. By incorporating command-line arguments, you can pass the mission name directly when executing the script, dramatically streamlining the process.
When a shell script runs, it automatically splits the command and its arguments. The script name is stored in the variable `$0`, while the first user-provided argument is stored in `$1`. Subsequent arguments are held in `$2`, `$3`, and so on. By replacing hard-coded values with these built-in variables, your script becomes universally reusable for any mission.
Using meaningful variable names (like `mission_name` instead of `$1` everywhere) improves the readability and maintainability of your code.
Below is the original version of the script that requires manual editing of the mission name:
```bash theme={null}
$ create-and-launch-rocket
$ # modify the create-and-launch-rocket
$ create-and-launch-rocket
mission_name= mars-mission
mkdir $mission_name
rocket-add $mission_name
rocket-start-power $mission_name
rocket-internal-power $mission_name
rocket-start-sequence $mission_name
rocket-start-engine $mission_name
rocket-lift-off $mission_name
rocket-status $mission_name
rocket_status=${rocket-status $mission_name}
echo "Status of launch: $rocket_status"
```
To eliminate the need for manual intervention, modify the script to accept the mission name as a command-line argument. You can run the script with the mission name like this:
```bash theme={null}
$ create-and-launch-rocket saturn-mission
```
Here is the updated version of the script that leverages the command-line argument:
```bash theme={null}
mission_name=$1
mkdir $mission_name
rocket-add $mission_name
rocket-start-power $mission_name
rocket-internal-power $mission_name
rocket-start-sequence $mission_name
rocket-start-engine $mission_name
rocket-lift-off $mission_name
rocket-status $mission_name
rocket_status=$(rocket-status $mission_name)
echo "Status of launch: $rocket_status"
```
In the revised script, the mission name is assigned from the first command-line argument (`$1`) to a variable called `mission_name`. This substitution makes the code reusable for any mission, eliminating the need for manual changes before each run.
Always design your scripts to be self-contained and reusable by allowing user inputs through command-line arguments rather than hard-coding values. This approach minimizes errors and improves efficiency.
