Bash scripting is among the most popular ways of automating repetitive tasks on the command line. One of the most common features of Bash scripts is string comparison.
String comparison refers to the process of comparing two or more string variables to determine if they are equal, unequal, or partially equal. In Bash, string comparison can be done in different ways, including equality comparison using “==”, inequality comparison using “!=”, partial string comparison with wildcard character, and comparing strings with user input values.
In this article, we will delve deeper into these methods and provide examples of how they can be used in Bash scripting. Equality Comparison using “==”
Equality string comparison in Bash is done using the “==” operator.
The “==” operator compares two strings and returns true if they are equal and false if they are not. To illustrate this, consider the example below:
“`
#!/bin/bash
str1=”Hello”
str2=”World”
if [[ $str1 == $str2 ]]; then
echo “Strings are equal”
else
echo “Strings are not equal”
fi
“`
The output of this script will be “Strings are not equal” since the two strings assigned to “str1” and “str2” are not equal. However, if you change the value of “str2” to “Hello”, the output of the script will be “Strings are equal”.
Inequality Comparison using “!=”
Inequality string comparison in Bash is done using the “!=” operator. The “!=” operator compares two strings and returns true if they are not equal and false if they are.
The example below illustrates how to use the “!=” operator:
“`
#!/bin/bash
str1=”Hello”
str2=”World”
if [[ $str1 != $str2 ]]; then
echo “Strings are not equal”
else
echo “Strings are equal”
fi
“`
The output of this script will be “Strings are not equal” since the two strings assigned to “str1” and “str2” are not equal. However, if you change the value of “str2” to “Hello”, the output of the script will be “Strings are equal”.
Partial String Comparison with Wildcard Character
In Bash, you can use the wildcard character “*” for partial string comparison. The “*” character is a special character that matches any number of characters.
The example below illustrates how to use the wildcard character for partial string comparison:
“`
#!/bin/bash
str1=”Hello World”
str2=”Hello”
if [[ $str1 == $str2* ]]; then
echo “The
first string starts with the second string”
else
echo “The
first string does not start with the second string”
fi
“`
The output of this script will be “The
first string starts with the second string” since the
first string assigned to “str1” starts with the string assigned to “str2”.
Comparing String with User Input Value
In Bash, you can compare a string with a user input value using the read command to accept input from the user. The example below illustrates how to compare a string with a user input value:
“`
#!/bin/bash
echo “Enter a word:”
read word
if [[ $word == “hello” ]]; then
echo “You entered hello!”
else
echo “You did not enter hello.”
fi
“`
The output of this script will depend on what the user enters. If the user enters “hello”, the output will be “You entered hello!”.
If the user enters anything
else, the output will be “You did not enter hello.”.
Conclusion
In conclusion, string comparison is a crucial feature of Bash scripting, and there are different ways of doing it. The “==” operator is used for equality comparison, the “!=” operator for inequality comparison, the “*” wildcard for partial string comparison, and the read command for comparing a string with a user input value.
Understanding string comparison in Bash can help simplify scripting and make automation much more ef
ficient. In summary, Bash scripting’s string comparison is vital in automating repetitive tasks on the command line.
Bash offers several methods to compare strings, including equality comparison using “==”, inequality comparison using “!=”, partial comparison with a wildcard character, and comparing strings with user input values. Understanding string comparison in Bash can simplify scripting and make automation more ef
ficient. Therefore, this article highlights the importance of string comparison in Bash scripting and provides examples of how it can be utilized.
By mastering string comparison, one can improve their Bash scripting skills and automate tasks more effectively.