Re: clerifying my previous question>hw i wld read a portion of file

Hi,

I sent a reply but it seems it did not make it... probably since I had an
attachement. Anyway, here goes...

A small program that scans a stream for a start token and optionally and end
token:

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;

/**
 * Scans a stream for a start and optionally and end token
 */
public class StreamFind {
    /**
     * Main
     * @param args the arguments
     * @throws Exception if an error occurs
     */
    public static void main(String[] args) throws Exception {
        if (args.length < 2) {
            System.err.println("usage: <file> <start token> [<end token>]");
            System.exit(-1);
        }
        int argNbr = 0;
        // assume platform default encoding is OK...
        InputStream is = new FileInputStream(args[argNbr++]);
        Reader br = new BufferedReader(new InputStreamReader(is));
        //
        String startToken = args[argNbr++];
        String endToken = args.length == 3 ? args[argNbr++] : null;
        //
        StringBuilder b = null;
        while (true) {
            if (b == null && peekForToken(startToken, br)) {
                b = new StringBuilder();
                b.append(startToken);
            } else if (endToken != null && b != null &&
peekForToken(endToken, br)) {
                b.append(endToken);
                break;
            } else {
                int c = br.read();
                if (c == -1) {
                    break;
                }
                if (b != null) {
                    b.append((char) c);
                }
            }
        }

        if (b != null) {
            System.out.println(b);
        }
        System.exit(b != null ? 0 : -1);
    }

    /**
     * Peeks in the stream to check if the specified token is found
     * @param token the token to look for
     * @param br the reader
     * @return <code>true</code> if the token is found, in this case the
stream is positioned
     * after the token, otherwise false and the stream is unchanged
     * @throws IOException
     */
    private static boolean peekForToken(String token, Reader br) throws
IOException {
        br.mark(token.length());
        boolean matching = true;
        for (int i = 0; matching && i < token.length(); i++) {
            int c = br.read();
            matching = c != -1 && c == token.charAt(i);
        }
        if (!matching) {
            br.reset();
        }
        return matching;
    }
}

If you disregard whitespace and only consider whitespace surrounded tokens a
java.util.Scanner can be used instead:

import java.io.File;
import java.util.Scanner;

public class ReadFile {
    public static void main(String[] args) throws Exception {
        if (args.length < 2) {
            System.err.println("usage: <file> <start token> [<end token>]");
            System.exit(-1);
        }
        int argNbr = 0;
        // assume platform default encoding is OK...
        Scanner scanner = new Scanner(new File(args[argNbr++]));
        //
        String startToken = args[argNbr++];
        String endToken = args.length == 3 ? args[argNbr++] : null;
        //
        StringBuilder b = null;
        while (scanner.hasNext()) {
            String t = scanner.next();
            if (b == null && t.equals(startToken)) {
                b = new StringBuilder();
                b.append(t);
            } else if (b != null && t.equals(endToken)) {
                b.append(t);
                break;
            } else if (b != null) {
                b.append(t);
            }
        }
        if (b != null) {
            System.out.println(b);
        }
        System.exit(b != null ? 0 : -1);
    }
}

Cheers,
Martin.

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