How to check the number of arguments in a shell script?

Checking the Number of Arguments in a Shell Script

In a shell script, you can check the number of arguments passed to the script using the special variable $#. This variable contains the number of arguments, excluding the script name itself.

Here's how you can use it:

#!/bin/bash

# Check the number of arguments
if [ "$#" -eq 0 ]; then
    echo "No arguments provided."
else
    echo "Number of arguments: $#"
fi

In this example, the script first checks if the value of $# is equal to 0, which means no arguments were provided. If that's the case, it prints a message indicating that no arguments were provided.

If the number of arguments is greater than 0, the script prints the number of arguments using the $# variable.

You can also use the $# variable to perform more complex checks or actions based on the number of arguments. For example:

#!/bin/bash

# Check the number of arguments
if [ "$#" -lt 2 ]; then
    echo "Usage: $0 <arg1> <arg2>"
    exit 1
fi

# Access the arguments
arg1="$1"
arg2="$2"
echo "Argument 1: $arg1"
echo "Argument 2: $arg2"

In this example, the script checks if the number of arguments is less than 2. If that's the case, it prints a usage message and exits with a non-zero status code (1) to indicate an error. If the number of arguments is at least 2, the script accesses the first and second arguments using $1 and $2, respectively.

By understanding how to check the number of arguments in a shell script, you can write more robust and flexible scripts that can handle different input scenarios.

The Mermaid diagram above illustrates the flow of the script, where it first checks the number of arguments using the $# variable, and then takes different actions based on the result.

By using the $# variable, you can write shell scripts that can adapt to different input scenarios, making your scripts more versatile and user-friendly.