Bash — Strings

String basics

#!/bin/bash

s="Hello, World!"

echo "Length: ${#s}"           # 13
echo "Substring: ${s:0:5}"    # Hello
echo "Replace: ${s/World/Bash}" # Hello, Bash!
echo "Uppercase: ${s^^}"      # HELLO, WORLD!
echo "Lowercase: ${s,,}"      # hello, world!

String comparison

#!/bin/bash

a="hello"
b="hello"
c="world"

[ "$a" = "$b" ] && echo "Equal"
[ "$a" != "$c" ] && echo "Not equal"
[ -z "$empty" ] && echo "Empty string"
[ -n "$a" ] && echo "Non-empty string"

String concatenation

#!/bin/bash

first="Hello"
second="World"
combined="$first $second"
echo "$combined" # Hello World

String length

#!/bin/bash

s="Hello"
echo "${#s}" # 5

Substring

#!/bin/bash

s="Hello, World!"
echo "${s:0:5}"   # Hello
echo "${s:7}"     # World!
echo "${s: -6}"   # World!

String replacement

#!/bin/bash

s="Hello, World!"
echo "${s/World/Bash}"    # Hello, Bash!
echo "${s//l/L}"          # HeLLo, WorLd!
echo "${s/#Hello/Hi}"    # Hi, World!
echo "${s/!//}"           # Hello, World

Quoting

#!/bin/bash

name="Alice"

# Double quotes: variable expansion
echo "Hello, $name"     # Hello, Alice

# Single quotes: literal
echo 'Hello, $name'     # Hello, $name

# Backslash: escape
echo "Price: \$100"     # Price: $100

Mini Practice

Write Bash code that:

1. Extracts a substring from a string
2. Replaces text in a string
3. Demonstrates quoting differences
4. Checks string length and emptiness

Up Next

In the next lesson, you'll learn about Numbers — arithmetic operations in Bash.