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Mastering File Comparison with Shell Scripting: Comparing ‘fileA.txt’ and ‘fileB.txt

   February 5, 2024

File comparison is a crucial task in various scenarios, whether you’re verifying data integrity, tracking changes, or ensuring consistency. In this article, we’ll explore how to create a Shell script to compare the contents of two files, ‘fileA.txt’ and ‘fileB.txt,’ and report whether they are the same or different. Understanding how to perform file comparisons using Shell scripting is a valuable skill for developers, system administrators, and anyone working with text-based data. We’ll provide step-by-step examples and demonstrate the expected output to help you master the art of file comparison.

Prerequisites:

Before we begin, ensure that you have the following prerequisites:

  1. A Unix-like operating system (e.g., Linux, macOS).
  2. Basic knowledge of using the command line and a text editor.

Writing the Shell Script:

Let’s create a Shell script that compares the contents of ‘fileA.txt’ and ‘fileB.txt’ and reports whether they are identical or different.

#!/bin/bash

# Define the file paths
fileA="fileA.txt"
fileB="fileB.txt"

# Compare the contents of the two files
if cmp -s "$fileA" "$fileB"; then
    echo "The contents of '$fileA' and '$fileB' are identical."
else
    echo "The contents of '$fileA' and '$fileB' are different."
fi

Explanation:

  • We start the script with the shebang #!/bin/bash, indicating that it should be interpreted using the Bash shell.
  • We define the file paths for ‘fileA.txt’ and ‘fileB.txt’ using variables fileA and fileB.
  • cmp -s "$fileA" "$fileB" is the command used to compare the contents of the two files. The -s flag ensures that the command operates silently, producing no output unless the files differ.
  • We use an if statement to check the exit status of the cmp command. If the exit status is 0 (indicating that the files are the same), it prints a message stating that the contents are identical. Otherwise, it reports that the contents are different.

Executing the Script:

To execute the script, follow these steps:

  1. Save the Shell script to a file with a .sh extension (e.g., file_comparison.sh).
  2. Open your terminal or command prompt and navigate to the directory where you saved the script.
  3. Make the script executable by running the command: 
    chmod +x file_comparison.sh

Run the script by executing:

./file_comparison.sh

Output:

Upon running the script, you will see one of the following outputs, depending on whether ‘fileA.txt’ and ‘fileB.txt’ are identical or different:

If the files are identical:

The contents of 'fileA.txt' and 'fileB.txt' are identical.

If the files are different:

The contents of 'fileA.txt' and 'fileB.txt' are different.
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