How to Call Another Script in Bash [2 Methods]

Calling another script within a Bash script is an important task. Once you call another script, the execution of the current script will temporarily pause and the code of the called script will be executed first.

It offers the user to write code in different scripts and facilitates modularity and reusability of the code. Moreover, scriptwriters can break down complex code into different and more manageable scripts. This article deals with various ways to call another script in Bash.

Key Takeaways

• Calling another script from the running script.
• Accessing variable and function of the calling script.
• Reasons for calling another function may not work.

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2 Methods to Call Another Script in Bash Script

There are mainly two ways of calling another script. One can call a script in the same process as the running script or can call the script in a different process. The two methods have some inherent differences that you can explore later in this article.

Method 1: Call and Run Another Script in the Same Process

One can call another process in the running script using the source command or its equivalent dot(.) operator. In this way, the calling method is executed in the running script’s process and the variables and functions of another script are accessible.

Steps to Follow >

❶ At first, launch an Ubuntu Terminal.

❷ Write the following command to open a file named same_process.sh in the build-in nano editor:

nano same_process.sh

❸ Copy the following scripts and paste them into nano. Press CTRL+O and ENTER to save the file; CTRL+X to exit. Alternatively, copy the following script. Paste the script in a text editor and save it as .sh file.

Script (same_process.sh) >

#!/bin/bash

# Prompt the user to enter a number
read -p "Please enter a number: " number

# Execute another script and pass the number as an argument
source ./same_process1.sh "$number"

Script (same_process1.sh) >

#!/bin/bash

# Prompt the user to enter another number
read -p "Please enter another number: " number2

# let's perform some operations with the numbers
result=$((number * number2))

# Display the result
echo "The multiplication of the numbers is: $result"

❹ Use the following two commands to make both file executable:

chmod u+x same_process.sh
chmod u+x same_process1.sh

❺ Run the same_process.sh script by the following command:

./same_process.sh

Here, you can see the user inputs 10 when the same_process.sh  prompts the user to input a number. After that, the script moves to another script namely same_process1.sh. This script prompts the user to input another number and the user again inputs 10. Then the program performs a multiplication operation and shows the result 100. The important thing to note here, using the source command you can access the variable and functions of the first script.

Method 2: Call and Run Another Script in a Different Process

You can call another Bash script in a completely different process than the running script. This way you can not access the variables and functions of the calling script in the main script.

Case 1: Use of “bash” Command

For this purpose, you can use the bash command or add the path of the calling script in the PATH variable. I am going to show you both processes.

Script (diff_process1.sh) >

#!/bin/bash
# Call and run another script in a different process
echo "This program will give the multiplication of two numbers."
bash ./diff_process2.sh

Script (diff_process2.sh) >

#!/bin/bash

read -p "Please enter a number: " number1
read -p "Please enter another number: " number2
result=$((number1 * number2))
echo "The multiplication of the numbers is: $result"

Run the main script by the following command:

./diff_process1.sh

Here, the main script displays a message informing you that the program will calculate the product of two numbers. After that, it starts to execute the diff_process2.sh file and prompts the user to input numbers. The user first inputs 10 and then 5. Then the program displays the multiplication result 50 as you can see in the image.

Case 2: Use of “export” Command to Call Another Script in Bash

Other way of calling another script in a different process is setting the path of the calling script in the PATH variable using the export command.

Script (path1.sh) >

#!/bin/bash

echo "This program will give the multiplication of two numbers."

# Add the path of path2.sh to $PATH
export PATH="$PATH:/home/laku"
# Call path2.sh as a normal command
path2.sh

Script (path2.sh) >

#!/bin/bash

read -p "Please enter a number: " number1
read -p "Please enter another number: " number2
result=$((number1 * number2))
echo "The multiplication of the numbers is: $result"

Run the main script by the following command:

./path1.sh

This time the main script displays the message that the program will calculate the product of two numbers. Then it moves to the script path2.sh. Later it seeks numbers from the user to input. The user first inputs 4 and then 5. Then the program displays the multiplication result 20 as you can see in the image.

Comparative Analysis of Methods

Here is a comparative analysis between the above-discussed methods. Take a look at the analysis to determine which method suits your needs best.

The choice between the two methods depends on the specific situation and it effects the script execution. I prefer running in a separate process because it is safer. However, if there is a need to access variables and functions from the calling script, running in the same process becomes necessary. The decision should be made based on the specific requirements and objectives.

Why Calling Another Script in Bash Not Working?

Calling another script in the running script may end up with an error due to insufficient knowledge of how a process runs. For example, look at the script below.

Script (issue1.sh) >

#!/bin/bash

echo "This program will give the multiplication of two numbers."
# Prompt the user to enter a number
read -p "Please enter a number: " number1
# Execute another script and pass the number>
export PATH="$PATH:/home/laku"
issue2.sh

Script (issue2.sh) >

#!/bin/bash

# Prompt the user to enter another number
read -p "Please enter another number: " number2

# let's perform some operations with the numbers
result=$((number1 * number2))

# Display the result
echo "The multiplication of the numbers is: $result"

Run the main script by the following command:

./issue1.sh

The expected result of the multiplication is 25. Though the issue1.sh calls the issue2.sh script properly but the program can’t perform the calculation. Because once the issue2.sh starts running it immediately terminates the process of issue1.sh script. Hence the number1 variable is not accessible from issue2.sh script.

Conclusion

In summary, calling another script in Bash is essential in many cases. I believe now you have a clear idea of how to call another script in a different process as well as with the running process of a script. I appreciate your valuable suggestions regarding this article. Thanks for reading.

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