Day 11 : Error Handling in Shell Scripting

Tasks:

Task 1: Checking Exit Status

Write a script that attempts to create a directory and checks if the command was successful. If not, print an error message.

Create a file:
```
 vim create_dir.sh
```

Enter the script in file:

 #!/bin/bash

 # Create directory
 mkdir /home/ubuntu/day11

 # Check exit status
 if [ $? -ne 0 ]; then
         echo "Directory was not created"
         exit 1
 fi
         echo "Directory created successfully"

Make it executable and execute. The OUTPUT will be:

Task 2: Using `if` Statements for Error Checking

Modify the script from Task 1 to include more commands (e.g., creating a file inside the directory) and use if statements to handle errors at each step.

#!/bin/bash

# Create directory inside directory
mkdir /home/ubuntu/day11/task2_dir
if [ $? -ne 0 ]; then
        echo "Failed to create Directory /home/ubuntu/day11/task2_dir "
        exit 1
fi

# Create file inside directory
touch /home/ubuntu/day11/task2_dir/newfile.txt
if [ $? -ne 0 ]; then
        echo "Failed to create file /home/ubuntu/day11/task2_dir/newfile.txt"
        exit 1
fi
        echo "Directory and file created successfully /home/ubuntu/day11/task2_dir/newfile.txt"

OUTPUT:

Task 3: Using `trap` for Cleanup

Write a script that creates a temporary file and sets a trap to delete the file if the script exits unexpectedly.

  #!/bin/bash

  # Create a temporary file
  tempfile="temp_file.txt"
  touch $tempfile

  # Trap to delete temporary file
  trap "rm -f $tempfile; echo 'Temporary file deleted'" EXIT

  # Stimualte with sleep (10 seconds)
  echo "Script running..."
  sleep 10

  echo "Script completed successfully"

OUTPUT: The script ran for 10 seconds and then temporary file deleted.

Task 4: Redirecting Errors

Write a script that tries to read a non-existent file and redirects the error message to a file called error.log.
```
  #!/bin/bash

  # Read non-existing file and redirect error
  cat non_existing_file 2> error.log
```
OUTPUT:

Task 5: Creating Custom Error Messages

Modify one of the previous scripts to include custom error messages that provide more context about what went wrong.

  #!/bin/bash

  # Create directory
  mkdir /home/ubuntu/task5_dir

  if [ $? -eq 0 ]; then
          echo "Directory created successfully"
  else
          echo "Failed: Directory was not created for /home/ubuntu/task5_dir. Check if you have required permissions!"
  fi

  # Create a file inside directory
  touch /home/ubuntu/task5_dir/myfile5.txt

  if [ $? -eq 0 ]; then
          echo "File created successfully"
  else
          echo "Failed: File was not created for /home/ubuntu/task5_dir/myfile5.txt. Check, your directory already exist and the file has its required permissions! "
  fi