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## 📝 Author

Birat Aryal — birataryal.github.io
Created Date: 2025-06-23
Updated Date: Monday 23rd June 2025 08:14:15
Website - birataryal.com.np
Repository - Birat Aryal
LinkedIn - Birat Aryal
DevSecOps Engineer | System Engineer | Cyber Security Analyst | Network Engineer

🧠 Bash if Conditionals

The if statement in Bash is used to perform conditional execution of commands. It forms the foundation for decision-making in scripts.

📐 Basic Syntax

Bash
if [ condition ]; then
    # commands
fi

With else

Bash
if [ condition ]; then
    # if-block
else
    # else-block
fi

With elif (else-if)

Bash
if [ condition1 ]; then
    # commands
elif [ condition2 ]; then
    # other commands
else
    # fallback
fi

🔎 Common Comparison Operators

Numeric

Operator Meaning
-eq equal
-ne not equal
-lt less than
-le less than or equal
-gt greater than
-ge greater than or equal

String

Operator Meaning
= or == equal
!= not equal
-z is empty
-n is not empty

File

Operator Meaning
-f file file exists and is a regular file
-d dir directory exists
-e path file or directory exists
-r readable
-w writable
-x executable

✅ Examples

1. Numeric Comparison

Bash
#!/bin/bash
num=5
if [ $num -gt 3 ]; then
    echo "$num is greater than 3"
fi

2. String Comparison

Bash
#!/bin/bash
name="Birat"
if [ "$name" = "Birat" ]; then
    echo "Welcome, $name!"
else
    echo "Access denied"
fi

3. Check if File Exists

Bash
#!/bin/bash
if [ -f "/etc/passwd" ]; then
    echo "File exists"
else
    echo "File not found"
fi

4. Nested if Statement

Bash
#!/bin/bash
num=10
if [ $num -gt 0 ]; then
    if [ $num -lt 100 ]; then
        echo "$num is between 1 and 99"
    fi
fi

5. if with Logical Operators

Bash
#!/bin/bash
age=25
if [ $age -gt 18 ] && [ $age -lt 30 ]; then
    echo "Eligible"
fi

Other logic options:

  • && (AND)

  • || (OR)

  • ! (NOT)

🔁 if in Loops (Example)

Bash
#!/bin/bash
for num in 1 2 3 4 5
do
    if [ $num -eq 3 ]; then
        echo "Three found!"
    else
        echo "$num"
    fi
done

Tips

Use [[ ... ]] for safer conditions

Bash
if [[ $string == "value" ]]; then
    echo "Match"
fi