Question

I have been scouring the Internet looking for a Java package/class that will allow me to parse the UNIX /etc/group file. While it really wouldn’t be so hard to write this from scratch, I’m quite surprised not to find something already out there. There is a POSIX passwd class (see http://www.bmsi.com/java/posix/docs/posix.Passwd.html), but I’m not finding a similar class for /etc/group. Does such a thing exist?

Answer 1

Heres my code that tofubeer updated that I updated again. His didn’t compile. missing InvalidGroupException class. Also, no package was specified. Switched EMPTY_LIST to emptyList() to avoid lack of parameterization.

package fileutils;  import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.List;  public class GroupReader2 {     public static class InvalidGroupException extends Exception {         private static final long serialVersionUID = 1L;          public InvalidGroupException(String string) {             super(string);         }     }      public static GroupReader2 parseGroup(final String groupLine)             throws InvalidGroupException {         final String line;         final String[] parts;          if (groupLine == null) {             throw new IllegalArgumentException('groupLine cannot be null');         }          line = groupLine.trim();          if (line.startsWith('#') || line.isEmpty()) {             return null;         }          parts = line.split(':');          if (parts.length < 3) {             throw new InvalidGroupException(groupLine                     + 'must be in the format of name:passwd:gid[:userlist]');         }          try {             final GroupReader2 group;             final String name;             final String passwd;             final int gid;             final List<String> userList;              name = parts[0];             passwd = parts[1];             gid = Integer.parseInt(parts[2]);              if (parts.length == 4) {                 userList = Arrays.asList(parts[3].split(','));             } else {                 userList = Collections.emptyList();             }              group = new GroupReader2(name, passwd, gid, userList);              return group;         } catch (final NumberFormatException ex) {             throw new InvalidGroupException(groupLine + ' gid must be a number');         }     }      private final int gid;     private final String name;     private final String passwd;      private final List<String> userList;      public GroupReader2(final String nm, final String pw, final int id,             final List<String> users) {         name = nm;         passwd = pw;         gid = id;         userList = Collections.unmodifiableList(new ArrayList<String>(users));     }      public int getGid() {         return (gid);     }      public String getName() {         return (name);     }      public String getPasswd() {         return (passwd);     }      public List<String> getUserList() {         return (userList);     }      @Override     public String toString() {         final StringBuilder sb;          sb = new StringBuilder();         sb.append(name);         sb.append(':');         sb.append(passwd);         sb.append(':');         sb.append(gid);         sb.append(':');          for (final String user : userList) {             sb.append(user);             sb.append(',');         }          sb.setLength(sb.length() - 1);          return (sb.toString());     } }