In the previous class, you created your first bash script, edited $PATH variables to create custom commands and added aliases to your ~$/.$bashrc file.

Now, we will add variables and conditional if statements to our scripts.

If statements improve our scripts by allowing us to:

Check if a file or directory exists before we create it$.$

Check what user has run the script.

And more...

To complete this activity, you will create variables and if statements that satisfy given requirements and use them in your script.

Instructions

Consult this list of bash conditional operators while completing the activity:

$=$ : Checks if two items are equal.

$!=$ : Checks if two items are not equal.

$-$gt : Checks if an integer is greater than another.

$-$lt : Checks if an integer less than another.

$-$d $/$path$\_$to$/$directory : Checks for existence of a directory.

&& : Both conditions have to be true to run.

$||$ : One condition has to be true to run.

Using Variables

Create a variable to hold the path of your output file.

Replace the output file path for each command with your variable.

Using If Statements

Create an if statement that checks for the existence of the ~$/$research directory.

If the directory exists, do nothing. If the directory does not exist, create it$.$

Remove the line in your script that creates this directory.

Create an if statement that checks for the existence of the file ~$/$research$/$sys$\_$info.txt$.$

If the file does not exist, do nothing.

If the file does exist, remove it$.($This will ensure that the script always creates a new file,$)$

Bonus Variables

If you have already completed the exercises above, see if you can complete the following:

Create a variable to hold the output of the command: ip addr $|$ grep inet $|$ tail $-2|$ head $-1.$

Replace this command in your script with your new variable.

Create a variable to hold the output of the command: find $/$home $-$type f $-$perm $777.$

Replace this command in your script with your new variable.

Bonus If Statement

Protect the script from root! Create an if statement that checks if the script was run using sudo.

If it was run with sudo, exit the script with a message that tells the user not to run the script using sudo.