Java Program to Implement Grep, Egrep and Fgrep Commands

This is a java program to implement grep linux command.

Here is the source code of the Java Program to Implement the Program Used in grep/egrep/fgrep. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

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package com.sanfoundry.setandstring;
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import java.io.BufferedReader;
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import java.io.FileReader;
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import java.io.IOException;
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import java.util.Scanner;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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public class GrepCommandImplementation
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{
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    public static void main(String[] argv) throws Exception

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    {
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        Scanner sc = new Scanner(System.in);

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        System.out
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                .println("Enter the string to match from GrepCommandImplementation.java file: ");

        Pattern pattern = Pattern.compile(sc.next());

        Matcher matcher = pattern.matcher("");

        String file = "src/com/sanfoundry/setandstring/GrepCommandImplementation.java";

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        BufferedReader br = null;
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        String line;
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        try
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        {
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            br = new BufferedReader(new FileReader(file));

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        }
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        catch (IOException e)
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        {
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            System.err.println("Cannot read '" + file + "': " + e.getMessage());

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        }
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        while ((line = br.readLine()) != null)

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        {
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            matcher.reset(line);
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            if (matcher.find())
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            {
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                System.out.println(file + ": " + line);

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            }
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        }
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        br.close();
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        sc.close();
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    }
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}
```

Output:

$ javac GrepCommandImplementation.java
$ java GrepCommandImplementation
 
Enter the string to match from GrepCommandImplementation.java file: 
println
src/com/sanfoundry/setandstring/GrepCommandImplementation.java:                 .println("Enter the string to match from GrepCommandImplementation.java file: ");
src/com/sanfoundry/setandstring/GrepCommandImplementation.java:             System.err.println("Cannot read '" + file + "': " + e.getMessage());
src/com/sanfoundry/setandstring/GrepCommandImplementation.java:                 System.out.println(file + ": " + line);

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