Check if file is already open

Question

I need to write a custom batch File renamer  I ve got the bulk of it done except I can t figure out how to check if a file is already open  I m just using the java io File package and there is a canWrite   method but that doesn t seem to test if the file is in use by another program  Any ideas on how I can make this work

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Hi I really hope this helps    I tried all the options before and none really work on Windows  The only think that helped me accomplish this was trying to move the file  Event to the same place under an ATOMIC MOVE  If the file is being written by another program or Java thread  this definitely will produce an Exception    try         Files move Paths get currentFile getPath                     Paths get currentFile getPath     StandardCopyOption ATOMIC MOVE             DO YOUR STUFF HERE SINCE IT IS NOT BEING WRITTEN BY ANOTHER PROGRAM     catch  Exception e             DO NOT WRITE THEN SINCE THE FILE IS BEING WRITTEN BY ANOTHER PROGRAM

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The Q amp A is about how to deal with Windows  open file  locks     not how implement this kind of locking portably    This whole issue is fraught with portability issues and race conditions    You could try to use FileLock  but it is not necessarily supported for your OS and or filesystem  It appears that on Windows you may be unable to use FileLock if another application has opened the file in a particular way  Even if you did manage to use FileLock or something else  you ve still got the problem that something may come in and open the file between you testing the file and doing the rename    A simpler though non-portable solution is to just try the rename  or whatever it is you are trying to do  and diagnose the return value and   or any Java exceptions that arise due to opened files     Notes    If you use the Files API instead of the File API you will get more information in the event of a failure  On systems  e g  Linux  where you are allowed to rename a locked or open file  you won t get any failure result or exceptions   The operation will just succeed   However  on such systems you generally don t need to worry if a file is already open  since the OS doesn t lock files on open

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org apache commons io FileUtils touch yourFile  doesn t check if your file is open or not  Instead  it changes the timestamp of the file to the current time     I used IOException and it works just fine   try      String filePath    C  sheet xlsx     FileWriter fw   new FileWriter filePath                      catch  IOException e        System out println  File is open

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If file is in use FileOutputStream fileOutputStream   new FileOutputStream file   returns java io FileNotFoundException with  The process cannot access the file because it is being used by another process  in the exception message

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TO CHECK WHETHER A FILE IS OPENED          OR NOT  not for  txt files           the file we want to check     String fileName    C   Text xlsx       File file   new File fileName           try to rename the file with the same name     File sameFileName   new File fileName        if file renameTo sameFileName               if the file is renamed         System out println  file is closed             else             if the file didnt accept the renaming operation         System out println  file is opened

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I don t think you ll ever get a definitive solution for this  the operating system isn t necessarily going to tell you if the file is open or not   You might get some mileage out of java nio channels FileLock  although the javadoc is loaded with caveats

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On Windows I found the answer https   stackoverflow com a 13706972 3014879 using   fileIsLocked    file renameTo file   most useful  as it avoids false positives when processing write protected  or readonly  files

User · Answer

Using the Apache Commons IO library     boolean isFileUnlocked   false  try       org apache commons io FileUtils touch yourFile       isFileUnlocked   true    catch  IOException e        isFileUnlocked   false     if isFileUnlocked          Do stuff you need to do with a file that is NOT locked    else          Do stuff you need to do with a file that IS locked

[java] Check if file is already open

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