// -*- java -*-

// smallest
// the smallest running program doing nothing
public class smallest { public static void main(String[] args) { } }

// hello world
// print a simple string on stdout
public class hello_world {
  public static void main(String[] args) {
    System.out.println("Hello World");
  }
}


// argv
// access command line parameters (no segmentation fault accepted, nor silent exception, so some languages must explicitly check the presence of the argument)
public class argv {
  public static void main(String[] args) {
    if (args.length > 0) System.out.println(args[0]);
  }
}


// env
// access environment variable
public class env {
    public static void main(String[] args) {
	System.out.println(System.getenv("HOME"));
    }
}


// test file exists
// return exit code error (non zero) if a file does not exist
public class exists {
  public static void main(String[] args) {
      if(!(new java.io.File("/etc/mtab")).exists()) System.exit(1);
  }
}


// test file readable
// return exit code error (non zero) if a file is not readable
public class readable {
  public static void main(String[] args) {
      if(!(new java.io.File("/etc/mtab")).canRead()) System.exit(1);
  }
}


// formatting
// print integers in a simple formatted string
public class formatting {
  public static void main(String[] args) {
    int a=1, b=2;
    System.out.println("" + a + " + " + b + " = " + (a + b));
  }
}


// system
// call an external program and check the return value
import java.io.*;
public class system {
  public static void main(String[] args) throws Exception {
    if (Runtime.getRuntime().exec("false").waitFor() != 0)
      System.err.println("false failed");
  
    BufferedReader input = new BufferedReader(new InputStreamReader(
        Runtime.getRuntime().exec("echo done").getInputStream()
    ));
    String line;
    while ((line = input.readLine()) != null)
      System.out.println(line);
  }
}


// sed in place
// remove #-comments from a file (modifying the file, i.e. in place)
import java.io.*;

public class uncomment {
    public static void main(String[] args) {
	try {
	    FileReader fr = new FileReader(args[0]);
	    BufferedReader br = new BufferedReader(fr);

	    File f = new File(args[0] + ".tmp");
	    FileWriter fw = new FileWriter(f);

	    String line = "";
	    while ((line = br.readLine()) != null) {
		int pos = line.indexOf('#');
		if (pos > -1) line = line.substring(0,pos);
		fw.write(line + '\n');
	    }
	    fr.close();
	    fw.close();
	    f.renameTo(new File(args[0]));
	} catch(Exception ex) {
	    ex.printStackTrace();
	}
    }
}


// compile what must be
// find and compile .c files into .o when the .o is old or absent
import java.io.*;

public class compile {
  public static void main(String[] args) {
      filter ft = new filter();
      if (args.length > 0) {
          File f = new File(args[0]);
          File[] cs = f.listFiles(ft);
	  for (int i = 0; i < cs.length; i++) tryFile(cs[i]);
      }
  }

  static void tryFile(File c) {
      String o = c.toString().replaceAll(".c$", ".o");
      File tmp = new File(o);
      if (!tmp.exists() || 
          tmp.lastModified() < c.lastModified()) {
          System.out.println("compiling " + 
                             c.toString() + " to " + o);
          String cmd = "gcc -c " + c.toString() + " -o " + o;
	  try {
	      java.lang.Runtime.getRuntime().exec(cmd);
          } catch(Exception ex) { ex.printStackTrace(); }
      }
  }
}

class filter implements FileFilter
{
  public filter() { }
  public boolean accept(File f) {
      return f.toString().endsWith(".c");
  }
}