Grepping class name if contains main function by bash script

user_10220825 0
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I am writing script that grep the class name of java file containing multiple class, if it contains main function. Example: My file contain text.txt

class Parent 
{
    public void p1()
    {
        System.out.println("Parent method");
    }
}
public class Child extends Parent {

    public static void main(String[] args)
    {
        Child cobj = new Child();
        cobj.c1();   //method of Child class
        cobj.p1();   //method of Parent class
    }
  public void c1()
    {
        System.out.println("Child method");
    }
}

Output will be: Child because it conatins main function. I analyze the pattern and grep two line before the pattern main found in a file. My script:

grep  -B 2 "public static void main" "text.txt" > sample.txt
filen=$(grep -oP '(?<=class )[^ ]*' sample.txt)
echo $filen

But my approach gets wrong if code contains like:

class Parent
{
    public void p1()
    {
        System.out.println("Parent method");
    }
}
public class Child extends Parent {
    public void c1()
    {
        System.out.println("Child method");
    }
    public static void main(String[] args)
    {
        Child cobj = new Child();
        cobj.c1();   //method of Child class
        cobj.p1();   //method of Parent class
    }
}

Please help me in finding correct approach.

sed awk
3 Answers

Could you please try following once.

 awk '/public static void main>/{print val} /public class/{val=$3}' Input_file
user_58665800

On Linux I would do it like this:

grep -e 'public class\|public static void main\>' text.txt  | grep -B1 "public static void main" | grep '\<class\>' | sed "s/^.*class \+//;s/ .*$//"
  • grep -e 'public class\|public static void main\>' text.txt: Grep all lines that either contain "public class" or "public static void main".
  • | grep -B1 "public static void main": grep the line containing "public static void main" and one line before.
  • | grep '\<class\>': Greps the line containing the word "class".
  • | sed "s/^.*class \+//;s/ .*$//": Get rid of everything around the class name.

Note \< and \> match word boundaries. So \<class\> matches the word "class" but not "declassified".

user_73692800

You can use Perl. The below works for both scenarios. Note that grep and awk may give incorrect results when you have more than 2 spaces between public/static/class etc

$ perl -0777 -ne ' /\bpublic\s+class\s+(\S+).+?public\s*static\s*void\s*main/ms and print "$1\n" ' arya2.txt
Child

$ cat arya2.txt
class Parent
{
    public void p1()
    {
        System.out.println("Parent method");
    }
}
public class Child extends Parent {
    public void c1()
    {
        System.out.println("Child method");
    }
    public static void main(String[] args)
    {
        Child cobj = new Child();
        cobj.c1();   //method of Child class
        cobj.p1();   //method of Parent class
    }
}
user_68670480
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