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Wildcard Deletion throughJava out-of-process

Posted on 2002-03-04
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Last Modified: 2010-03-31
I'm running JDK 1.3 under Unix environment.  If I want to delete all .pdf files in a directory, I can do so on the command line by just typing "rm *.pdf".  But I'm having problems doing this through Java, such as the following:

try
      {
          String commandString = "rm *.pdf";
          Process p = Runtime.getRuntime().exec(commandString);
          p.waitFor();
          p.destroy();
          System.out.println("done");
      }
      catch (Exception e)
      {
          e.printStackTrace();
      }

If I specify a file exactly (like a.pdf), it does delete that specific file.  But if I use the wildcard (*), nothing happens.  How can I delete using wildcard?  Thanks in advance.
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Question by:jove
6 Comments
 
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Accepted Solution

by:
m_onkey_boy earned 100 total points
ID: 6839904
This should work.  The structure of Wildcard filter may be modified to parse wildcards and such, but this is the general idea....:

File f = new File(strReadDir);
               String[] aList = f.list(new WildcardFilter("pdf"));

for (int i = 0; i < aList.length; i++)
     aList[i].delete();

class WildcardFilter implements FilenameFilter {
     private String m_strFileSuffix = null;
         
     public XsltFilter(String strFileSuffix) {
          m_strFileNameSuffix = strFileSuffix;
     }
         
     public boolean accept (File f, String strFileName) {
          return strFileName.toLowerCase().endsWith(strFileSuffix);
     }
}
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Expert Comment

by:saxaboo
ID: 6839922
Hi,

I gather this comes from the fact you need a shell to interpret the wildcards.

Had you been in an NT environment, with a "del *.pdf" command, I would have suggested to replace it by "start del *.pdf"

I'm sure you can do something similar under Unix, by invoking bash or tcsh and passing it your command-line on the standard input, but I'm not sure of the syntax and haven't got any Unix prompt anywhere next to me. A heavier way to do this would be to have a shell script delpdf.sh containing your command, and to call "sh delpdf.sh"

Hope this helps,

-S
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Expert Comment

by:saxaboo
ID: 6839929
Oops, concurrent answer !

Sorry m_onkey_boy for my first line about wildcards ;-)
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LVL 5

Expert Comment

by:kelfink
ID: 6839931
On UNIX, it's the shell process which performs the wildcard.  Calling 'rm' directly bypasses this.

MonkeyBoy's suggestion is good for rolling your own wildcard implementation.  

If your goal is to pass commands to Unix, you have to get the Shell to process the arguments.

Example to modify your original post:

         String[] cmd = { "/bin/sh", "-c", "rm *.pdf" };
         Process p = Runtime.getRuntime().exec(cmd);

works.



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LVL 4

Expert Comment

by:m_onkey_boy
ID: 6839989
Another note:  My solution will take a bit longer to write code-wise, but it has the advantages of being platform-independant and faster that calling exec().

The main drawback is that you have to write your own parsing routines that are already in place for you by the OS.
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Author Comment

by:jove
ID: 6839993
Thanks much.
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