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You're developing a Bash script that reads lines from a text file. If a line contains the word "error," the script should display an error message and continue reading the next line. If a line contains the word "success," it should display a success message and break out of the loop. For all other lines, it should display a generic message. Which code snippet correctly implements this behavior using a while loop?

Question

You're developing a Bash script that reads lines from a text file. If a line contains the word "error," the script should display an error message and continue reading the next line. If a line contains the word "success," it should display a success message and break out of the loop. For all other lines, it should display a generic message. Which code snippet correctly implements this behavior using a while loop?

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Solution

Here is a Bash script that implements the described behavior:

#!/bin/bash

while IFS= read -r line
do
  if [[ $line == *"error"* ]]; then
    echo "Error message"
  elif [[ $line == *"success"* ]]; then
    echo "Success message"
    break
  else
    echo "Generic message"
  fi
done < "file.txt"

Here's how it works:

  1. #!/bin/bash is the shebang that tells the system this is a bash script.
  2. while IFS= read -r line starts a while loop that reads from the file line by line. IFS= prevents leading/trailing whitespace from being trimmed. -r prevents backslashes from being escaped.
  3. do ... done defines what is done in each iteration of the loop.
  4. if [[ $line == *"error"* ]]; then checks if the line contains the word "error". If it does, it prints "Error message".
  5. elif [[ $line == *"success"* ]]; then checks if the line contains the word "success". If it does, it prints "Success message" and breaks the loop.
  6. else is for all other lines, it prints "Generic message".
  7. < "file.txt" is the input redirection that feeds the file into the loop. Replace "file.txt" with the name of your file.

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