Running a Basic Script

Bash scripting allows users to automate tasks, execute commands in sequence, and simplify repetitive operations.

1. Create the Script File

First, create a script file using the vi editor.

vi script.sh

Press i to enter insert mode, then write a simple script.

To save and exit:

Press Esc
Type :wq
Press Enter

2. Try to Run the Script

Now try to execute the script. You may see an error like this:

This happens because the script does not have execute permission.

3. Check File Permissions

Use the following command to see the file permissions:

ls -ltr

Output:

rw- → owner can read and write
r-- → group can read
r-- → others can read

4. Add Execute Permission

To allow the script to run, add execute permission:

chmod +x script.sh

5. Verify the Permission Change

Run ls -ltr again:

ls -ltr

Now the output should look like:

Notice the x in the permissions:

-rwxr-xr-x

This means the script can now be executed.

6. Run the Script Again

Execute the script again:

./script.sh

Output:

The script now runs successfully.

Lesson Learned

From this exercise, we learn several important things about running Bash scripts.

1. A Script Must Have Execute Permission

Even if the script is written correctly, it cannot run without execute permission.

Linux requires the x permission for a file to be executed as a program.

chmod +x script.sh

2. What `+x` Means

The command:

chmod +x script.sh

is used to add execute permission to the file.

Explanation:

chmod → command used to change file permissions
+ → means add permission
x → means execute permission

So:

+x

means add the execute permission to the file. This allows the system to run the script like a program.

3. File Permissions Can Be Checked

ls -ltr

This command shows whether a file has:

r → read
w → write
x → execute

permissions.

4. The Shebang is Important

At the top of the script we used:

#!/bin/bash

This tells the system which interpreter should run the script.