107 Relational Operators in Shell Scripting

Relational operators in shell scripting are used to compare values and make decisions based on those comparisons. These operators are particularly useful in conditional statements and loops. Here’s a comprehensive overview of relational operators in shell scripting, including their usage and examples.

1. Numeric Comparison Operators
These operators are used to compare integers.

Operator Description Example

#!/bin/bash

a=10
b=20

if

fi
2. String Comparison Operators
These operators are used to compare strings.

Operator Description Example

bash
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#!/bin/bash

str1="apple"
str2="banana"

if [ "$str1" != "$str2" ]; then
echo "$str1 is not equal to $str2"
fi
3. Using [[ ]] for Comparisons
The double brackets provide a more flexible and powerful way to perform comparisons, especially for strings. It supports pattern matching and logical operators.

Example with [[ ]]
bash
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#!/bin/bash

number=5

if [[ $number -gt 0 ]]; then
echo "$number is positive."
fi

string1="hello"
string2="hello"

if [[ $string1 == $string2 ]]; then
echo "The strings are equal."
fi
4. Combining Conditions
You can combine multiple relational operators using logical operators like && (AND) and || (OR).

Example of Combining Conditions
bash
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#!/bin/bash

num=15

if [[ $num -gt 10 && $num -lt 20 ]]; then
echo "$num is between 10 and 20."
fi
Conclusion
Relational operators in shell scripting are crucial for performing comparisons and making decisions based on those comparisons. By understanding and using these operators effectively, you can create more dynamic and responsive scripts that can handle various conditions and inputs.