Linux expr Guide

Complete beginner-friendly guide to expr on Linux, covering Arch Linux, CachyOS, and other distributions including arithmetic operations, string operations, and expression evaluation.

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Table of Contents

1. expr Basics
2. Arithmetic Operations
3. String Operations
4. Pattern Matching
5. Troubleshooting

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expr Basics

Arithmetic

Basic usage:

# Addition
expr 5 + 3

# Output: 8

Note on Spaces

Important:

# Spaces required around operators
expr 5 + 3    # Correct
expr 5+3      # Wrong (no spaces)

# Must have spaces around +, -, *, etc.

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Arithmetic Operations

Basic Math

Operations:

# Addition
expr 10 + 5

# Subtraction
expr 10 - 5

# Multiplication (escape *)
expr 10 \* 5

# Division
expr 10 / 5

# Modulo
expr 10 % 3

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String Operations

String Length

Length:

# String length
expr length "Hello World"

# Output: 11

Substring

Extract substring:

# Substring
expr substr "Hello World" 1 5

# substr string start length
# Output: Hello

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Pattern Matching

Match Pattern

Pattern match:

# Match pattern
expr "Hello" : ".*"

# : = match operator
# Returns length if match

Extract Match

Get match:

# Extract matched part
expr "Hello World" : "\(.*\) World"

# \( \) = capture group
# Output: Hello

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Troubleshooting

expr Not Found

Check installation:

# expr is part of coreutils
# Usually pre-installed

# Check expr
which expr

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Summary

This guide covered expr usage, arithmetic, string operations, and expression evaluation for Arch Linux, CachyOS, and other distributions.

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Next Steps

• Bash Scripting Guide - Scripting basics
• bc Guide - Calculator
• awk Guide - Advanced text processing
• expr Documentation: man expr

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This guide covers Arch Linux, CachyOS, and other Linux distributions. For distribution-specific details, refer to your distribution's documentation.