BibtexClean.java

package plume;

import java.io.*;
import java.util.*;
import java.util.regex.*;
import java.nio.CharBuffer;

/**
 * Clean a BibTeX file by removing text outside BibTeX entries.
 *
 * Remove each non-empty line that is not in a BibTeX entry, except retain
 * any line that starts with "%".
 *
 * Arguments are the names of the original files.  Cleaned copies of those
 * files are written in the CURRENT DIRECTORY.  Therefore, this should be
 * run in a different directory from where the argument files are, to avoid
 * overwriting them.
 */

// The implementation uses regular expressions rather than a BibTeX parser,
// because BibTeX parsers generally do not preserve formatting, such as
// indentation, delimiter characters, and order of fields.  And, the ones I
// looked at were not very well-documented.

// The implementation cannot use EntryReader to iterate through the file
// because the @ line does not necessarily follow a blank line -- there
// might be a comment line before it.  But, EntryReader requires that its
// "long entries" start after a blank line.  (That can be considered an
// EntryReader bug, or at least inflexibility in its interface.)

public class BibtexClean {

  private static Pattern entry_end = Pattern.compile("^[ \t]*(?i)(year[ \t]*=[ \t]*[12][0-9][0-9][0-9][ \t]*)?[)}]");
  private static Pattern stringDef = Pattern.compile("^@(?i)string(\\{.*\\}|\\(.*\\))$");

  public static void main(String[] args) {
    for (String filename : args) {
      File in = new File(filename);
      PrintWriter out;
      try {
        out = new PrintWriter(UtilMDE.bufferedFileWriter(in.getName())); // in current directory
      } catch (IOException e) {
        System.err.println("Unable to write " + in.getName());
        System.exit(2);
        throw new Error("This can't happen"); // for definite assignment check
      }
      EntryReader er;
      try {
        er = new EntryReader(filename);
      } catch (IOException e) {
        System.err.println("Unable to read " + in);
        System.exit(2);
        throw new Error("This can't happen"); // for definite assignment check
      }
      for (String line : er) {
        if (line.equals("") || line.startsWith("%")) {
          out.println(line);
        } else if (line.startsWith("@")) {
          if (stringDef.matcher(line).matches()) {
            out.println(line);
          } else {
            out.println(line);
            while (er.hasNext() && ((line = er.next()) != null)) {
              out.println(line);
              if (entry_end.matcher(line).lookingAt()) {
                break;
              } else if (line.equals("")) {
                System.err.printf("%s:%d: unterminated entry%n",
                                  er.getFileName(), er.getLineNumber());
                break;
              }
            }
          }
        }
      }
      out.close();
    }
  }

}