Diffutils To Show File Differences

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Diff Command Compares Files

GNU Diffutils is a package of multiple applications related to finding differences between files. One of the applications is the diff command that display differences between the contents of 2 files.

The file comparison utility diff outputs differences between 2 files. The diff command outputs line by line in multiple formats based on the command line options.

Identical files will not produce an output. Binary files will be reported as different only.

The focus of this tutorial will be on the differences between 2 text files and 2 binary files.

  1. Creating 2 files.
  2. Running the diff command on the 2 files.
  3. Explaining the output diff or patch.

Requirements For Using Diff

Glossary:

Patch

Set of differences.

Binary File

Computer file that is not a text file.

Tools

Programming Tools
Name Description Example
Bitmap editor For creating and editing bitmap images Apache Netbeans IDE
Text editor For creating and editing source code GNU Image Manipulation Program (GIMP)
SSH Secure Shell Client OpenSSH
Shell Access Access to the command line. Terminal
Diff File comparison utility. diff
Name Description Example

Create First Text File

# Create New Text File #
cat > test1.txt << 'EOF'
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EOF

Create Second Text File

# Clone New Text File #
cp test1.txt test2.txt

Create Third Text File

# Create New Text File #
cat > test3.txt << 'EOF'
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EOF

Compare Any Two Files

# Compare Files With Diff #
diff test1.txt test2.txt
diff test1.txt test3.txt
diff test1.jpg test2.jpg
diff test1.jpg test3.jpg

Save Patch

# Save Differences #
diff test1.txt test2.txt > diff1.txt
diff test1.txt test3.txt > diff2.txt
diff test1.jpg test2.jpg > diff3.txt
diff test1.jpg test3.jpg > diff4.txt

Explanation:

  1. The first and second files are the same.
  2. The first and third files are different.
  3. Binary files out only state if they “differ”.
  4. The “2,3c2,3” means that lines 2 and 3 are different.
  5. The less than symbol (<) is the second file in the diff command.
  6. The greater than symbol (>) is the first file in the diff command.

The diff command will compares 2 files and output any changes. The output contains the line numbers of the applicable changed lines.

Diff Two Files
Diff Of Two Files Both Text And Binary


Usage

You can use any IDE or text editor and the command-line or a web browser (if applicable) to run Diff commands. For this tutorial, Diff was used on ext files and binary files. Diff is cross-platform compatible (Unix, Linux, MacOS and Windows). Diff can be downloaded from GNU Diffutils.

Open Source

Diffutils is licensed under the GNU General Public License Version 3.0 or later. The copyleft license comes with strict rules and requirements to ensure the software remains free and open-source. It allows commercial use, modification, distribution, and allows making derivatives proprietary, consult the license for more specific details.

Conclusion:

The file comparison tool “diff” is a command line utility used to output changes between files. The output contains the affected line numbers. The output also shows the content of the affected line numbers preceding a greater than or less than symbol..

The programmer can determine to revert changes based on the line number output. The affected line number output is based on the order in which the “diff” command was used.

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