4: Bash Shell Scripting
- Page ID
- 414179
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What is Shell Scripting?
Shell scripting is a part of the automation process in Linux. Scripting allows writing a sequence of commands in a file and executing them.
It helps in saving time because the user won't have to repeat writing commands. They can schedule tasks for automatic execution. They can also make scripts that are executable on startup.
What is Bash Shell?
It is the default shell for many Linux distributions. Its script is generally located in the .bashrc file, which allows the customization of the shell.
What is a Bash Script?
A Bash script is a file containing a collection of commands that are read and executed by the Bash program.
A Bash script is characterized by:
- its file extension .sh
- needing the execution rights (x) added to the file in order to be able to execute via Bash shell
- being executable through an absolute path, through a "Shebang"
Shebang is composed of "bash = #" and "bang = !" and the path of the Bash shell.
It is added to the first line of the script and its function is to make the shell execute the script via Bash shell.
One example of a Shebang is #! user/bin/bash
Operations on Bash script
Setting the Bash interpreter and making it executable
Let's create a Bash script by making a new file and adding some content to it.
Creating the file using the command:
- cat > test.sh
cat > test.sh cat test.sh
Adding a command to the content of the file using the nano editor:
nano test.sh
and then in the script run an echo function to print a sentence to the screen once the bash script is run
nano test.sh echo "this is a test sentence"
- Output
-
Running the file with Bash using the command:
- bash test.sh
bash test.sh
- Answer
-
Checking the permissions of the file:
- ls -l test.sh
ls -l test.sh
- Output
-
Notice that the file doesn't have execution permissions. Thus it cannot be executed via Bash.
Thus, let's make it executable and then check that the permissions changed:
- chmod +x test.sh
chmod +x test.sh ls -l test.sh
- Output
-
Now, we are able to run our script with the default interpreter without having to use the "bash" command, as follows:
- ./test.sh
./test.sh
- Output
-
