rev

text processingLinux/Unix

The rev command is one of the most frequently used commands in Linux/Unix-like operating systems. rev Reverse lines of a file or standard input

See Examples View Syntax

Quick Reference

Command Name:

rev

Category:

text processing

Platform:

Linux/Unix

Basic Usage:

rev [options] [arguments]

Common Use Cases

Syntax

rev [file...]

Options

Option	Description
`--help`	Display help message and exit
`--version`	Output version information and exit

Examples

How to Use These Examples

The examples below show common ways to use the rev command. Try them in your terminal to see the results. You can copy any example by clicking on the code block.

# Basic Examples Basic

rev file.txt

Reverse each line of file.txt.

echo "Hello, World!" | rev

Reverse the text "Hello, World!".

# Advanced Examples Advanced

cat file.txt | rev | rev

Reverse each line and then reverse it again (results in original text). rev < input.txt > reversed.txt Reverse all lines from input.txt and save to reversed.txt. echo "palindrome" | rev Check if a word is a palindrome by comparing with the original. find . -name "*.txt" -exec rev {} \; | sort Reverse the contents of all text files and sort the output. rev file.txt | grep "txet" Find lines that end with "text" when read normally. for word in $(cat wordlist.txt); do if [ "$word" = "$(echo $word | rev)" ]; then echo "$word is a palindrome" fi done Find all palindromes in a word list. rev /etc/passwd | cut -d: -f1 | rev Extract the first field from /etc/passwd (usernames). echo "Text with (nested [brackets])" | rev See how nested brackets appear when text is reversed.

Try It Yourself

Practice makes perfect! The best way to learn is by trying these examples on your own system with real files.

Understanding Syntax

Pay attention to the syntax coloring: commands, options, and file paths are highlighted differently.

Notes

The `rev` command is a simple yet useful utility in Unix/Linux systems that reverses the characters in each line of a given file or standard input. It reads each line of input, reverses the order of characters, and outputs the result. Despite its simplicity, `rev` has various practical applications in text processing, scripting, and data manipulation tasks. It's part of the standard set of text processing utilities available in most Unix-like operating systems. Key features and characteristics of the `rev` command include: 1. Line-by-line Processing: It processes each line independently, preserving the line structure of the input. 2. Character-level Reversal: All characters in each line are reversed, including whitespace and special characters. 3. Stream Processing: Like many Unix utilities, it can process data from files or as part of a pipeline. 4. UTF-8 Support: Modern implementations typically handle UTF-8 encoded text correctly, reversing multi-byte characters as single units. Common use cases for the `rev` command include: - Identifying palindromes (words or phrases that read the same backward as forward) - Text obfuscation or simple encoding techniques - String manipulation in shell scripts - Pattern matching on reversed text (finding strings by their ending patterns) - Data transformation tasks in text processing pipelines - Educational demonstrations of text manipulation - Creating word puzzles or games While `rev` is not as commonly used as other text processing tools like `grep`, `sed`, or `awk`, it fills a specific niche and can be particularly handy when combined with other commands in a pipeline. For example, a common idiom is to use `rev` twice in a pipeline to operate on the end of fixed-width fields. By reversing the text, performing operations, and then reversing again, you can effectively process text from right to left instead of the usual left to right. The `rev` command is straightforward to use, with minimal options, making it accessible even to beginners. It's a good example of the Unix philosophy of creating simple tools that do one thing well and can be combined with other tools for more complex operations.

Related Commands

These commands are frequently used alongside rev or serve similar purposes:

Use Cases

Learn By Doing

The best way to learn Linux commands is by practicing. Try out these examples in your terminal to build muscle memory and understand how the rev command works in different scenarios.

See Examples Try Lab Exercises

$ rev

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