Skip to content

## 📝 Author

Birat Aryal — birataryal.github.io
Created Date: 2025-06-23
Updated Date: Monday 23rd June 2025 08:17:52
Website - birataryal.com.np
Repository - Birat Aryal
LinkedIn - Birat Aryal
DevSecOps Engineer | System Engineer | Cyber Security Analyst | Network Engineer

🔁 Bash for Loops

The for loop in Bash is used to iterate over a list of items, numeric ranges, or file patterns.

📐 Basic Syntax

Bash
for variable in list
do
    # commands
done

✅ Common Examples

1. Loop Over a List of Words

Bash
#!/bin/bash
for name in Alice Bob Charlie
do
    echo "Hello, $name!"
done

2. Loop Over a Range of Numbers (Brace Expansion)

Bash
#!/bin/bash
for i in {1..5}
do
    echo "Number: $i"
done

3. Loop Over Files

Bash
#!/bin/bash
for file in *.txt
do
    echo "Found file: $file"
done

4. Loop Over Command Output

Bash
#!/bin/bash
for user in $(cut -d: -f1 /etc/passwd)
do
    echo "User: $user"
done

🧱 Nested for Loops

Bash
#!/bin/bash
for i in 1 2 3
do
    for j in a b
    do
        echo "i=$i, j=$j"
    done
done

⛔ Loop Control: break & continue

Example: Skip an Item with continue

Bash
for i in {1..5}
do
    if [ $i -eq 3 ]; then
        continue
    fi
    echo "i=$i"
done

Example: Exit Early with break

Bash
for i in {1..5}
do
    if [ $i -eq 3 ]; then
        break
    fi
    echo "i=$i"
done

🔄 Combining with Conditionals

Bash
#!/bin/bash
for i in {1..10}
do
    if (( i % 2 == 0 )); then
        echo "$i is even"
    else
        echo "$i is odd"
    fi
done

📦 Loop Over Arguments ($@)

Bash
#!/bin/bash
for arg in "$@"
do
    echo "Argument: $arg"
done

Run with:

Bash
./script.sh apple banana cherry

🧠 Tips

  • Use quotes ("$var") to handle spaces

  • Use [[ ... ]] for safer condition checks

  • Use set -x to debug loop behavior