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95 lines
2.5 KiB
Java
95 lines
2.5 KiB
Java
Grep
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import java.io.*;
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import java.nio.*;
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import java.nio.channels.*;
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import java.nio.charset.*;
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import java.util.regex.*;
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public class Grep {
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// Charset and decoder for ISO-8859-15
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private static Charset charset = Charset.forName("ISO-8859-15");
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private static CharsetDecoder decoder = charset.newDecoder();
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// Pattern used to parse lines
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private static Pattern linePattern
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= Pattern.compile(".*
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?
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");
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// The input pattern that we're looking for
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private static Pattern pattern;
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// Compile the pattern from the command line
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//
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private static void compile(String pat) {
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try {
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pattern = Pattern.compile(pat);
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} catch (PatternSyntaxException x) {
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System.err.println(x.getMessage());
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System.exit(1);
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}
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}
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// Use the linePattern to break the given CharBuffer into lines, applying
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// the input pattern to each line to see if we have a match
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//
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private static void grep(File f, CharBuffer cb) {
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Matcher lm = linePattern.matcher(cb); // Line matcher
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Matcher pm = null; // Pattern matcher
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int lines = 0;
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while (lm.find()) {
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lines++;
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CharSequence cs = lm.group(); // The current line
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if (pm == null)
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pm = pattern.matcher(cs);
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else
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pm.reset(cs);
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if (pm.find())
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System.out.print(f + ":" + lines + ":" + cs);
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if (lm.end() == cb.limit())
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break;
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}
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}
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// Search for occurrences of the input pattern in the given file
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//
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private static void grep(File f) throws IOException {
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// Open the file and then get a channel from the stream
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FileInputStream fis = new FileInputStream(f);
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FileChannel fc = fis.getChannel();
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// Get the file's size and then map it into memory
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int sz = (int)fc.size();
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MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, sz);
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// Decode the file into a char buffer
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CharBuffer cb = decoder.decode(bb);
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// Perform the search
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grep(f, cb);
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// Close the channel and the stream
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fc.close();
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}
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public static void main(String[] args) {
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if (args.length < 2) {
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System.err.println("Usage: java Grep pattern file...");
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return;
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}
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compile(args[0]);
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for (int i = 1; i < args.length; i++) {
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File f = new File(args[i]);
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try {
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grep(f);
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} catch (IOException x) {
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System.err.println(f + ": " + x);
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}
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}
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}
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}
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