cat Command: Read and Combine File Contents in Linux

The cat command short for concatenate, It is a fast and versatile tool for viewing and merging file contents directly from the Linux terminal. Whether you’re inspecting logs or quickly joining multiple text files, cat delivers what you need with efficient simplicity.

How cat Works

You use cat to display the contents of files. Simply run:

cat filename.txt

cat filename.txt

You’ll instantly see everything written in the file printed to your screen. If you want to review the contents of several files at once, list them in sequence:

cat filename1.txt filename2.txt filename3.txt

cat filename1.txt filename2.txt filename3.txt

The result is that cat outputs all three files’ data in order.

Basic Syntax

cat [OPTION] [FILE]

cat [OPTION] [FILE]

• [OPTION]: Command-line options to modify output
• [FILE]: The target file(s) for processing

Common cat Command Uses

1. View a Single File

Display file content directly:

cat report.txt

cat report.txt

2. View Multiple Files

Show the contents of files in succession:

cat intro.txt summary.txt

cat intro.txt summary.txt

3. Show File with Line Numbers

Make each line identifiable for reviews or troubleshooting:

cat -n server.log

cat -n server.log

4. Create a New File

Quickly create and populate a file by typing text followed by Ctrl+D to save:

cat > notes.txt

cat > notes.txt

5. Copy or Merge Files

Merge multiple files into a new one:

cat part1.txt part2.txt > merged.txt

cat part1.txt part2.txt > merged.txt

6. Squeeze Blank Lines

Suppress repeated empty lines in output:

cat -s messy.txt

cat -s messy.txt

7. Append to an Existing File

Add content to the end of a file:

cat changelog.txt >> history.txt

cat changelog.txt >> history.txt

8. Highlight End of Lines

Show the $ at the end of every line for clarity:

cat -E notes.txt

cat -E notes.txt

9. All Text Files at Once

Display all text files in a folder:

cat *.txt

cat *.txt

Useful cat Command Options

Conclusion

From viewing a small config file to merging hundreds of logs for analysis, cat is a fundamental Linux skill that increases productivity at the terminal. Its versatility means every user, whether new or advanced benefits from mastering it.

Read More: History of Linux