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percentage counter in a command window

Posted on 2003-10-27
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Last Modified: 2008-02-20
I am trying to implement a counter on a command line that counts how much, % wise a file has been tranfered from a client to a server.

I was just wondering how I would be able to update the % on the same line in a System.out.println(""); command, so that I wouldnt have to have multiple lines in the terminal.

An example is like when you format your Hard Drive in DOS and it says 1% complete etc all the way up to 100%, thats what I am trying to acheive.


Thanks for any help.

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Question by:welsh_boy
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Expert Comment

by:CEHJ
ID: 9629746
Can't be done on the command line without using special JNI-based APIs
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Expert Comment

by:CEHJ
ID: 9629870
I just had an idea and tried this. Perhaps you can do something with it?

for(int i = 0;i < 10;i++) {
          System.out.print(i);
          Thread.sleep(1000);
          System.out.print('\010');
}
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Expert Comment

by:smitty22
ID: 9629881
What you could do instead is something like this:

0%                                                                               100%
|||||||||||||||||||||||||

Where you print the first line, calculate your scale based on file size (i.e. how much of the file does one "|" count for, then just use System.out.print("|") to print out another bar on the same line when the next unit has been transferred.
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Author Comment

by:welsh_boy
ID: 9629979
good idea smitty.

I have a giveFileLength() method so I can get the size of a file (as long). And each packet that is tranfered is Max 128 bytes, with 1 byte being a packet code, so effectivly I have a max of 127bytes of the file coming over at one time.


pseudo code so far.

System.out.print("0%                                               100%")
while (packetsrecived < giveFileLength())
{
System.out.print("|")
}

Not sure how to further implement it
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Expert Comment

by:CEHJ
ID: 9629999
And did you get the code i posted working? ;-)
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Assisted Solution

by:smitty22
smitty22 earned 100 total points
ID: 9630161
You will probably want to set the number of bars to use ahead of time.  The code you have so far will probably print a large number of bars by the time the file downloads.

I would choose something between 40-60 characters long, then before each file is downloaded calculate how many bytes one bar stands for.

So if you use 40 bars = 100%, then for an 80 byte file each bar would represent 2 bytes.  So, after downloading 2 bytes, you would _then_ print out the next bar.

There are a number of ways you could implement this, but you could keep track of how many bars you've printed so far, then use packetsreceived to calculate how many more you need to print out to accurately represent the current download state.


**NOT TESTED**
> assuming packetsreceived is the number of bytes received so far

System.out.print("0%                                  100%");  // total width of 40 characters
int scale = fileSize / 40;
int count = 0;
int calc;
while ( packetsreceived < fileSize ) {
   calc = packetsreceived / scale;
   if ( calc > count  ) {
      for ( ; count <= calc; count++ ) {
         System.out.print("|");
      }
   }
}
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Expert Comment

by:smitty22
ID: 9630165
I guess you could get rid of the if(calc > count) b/c it's taken care of in the for loop.
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Author Comment

by:welsh_boy
ID: 9630172
yeh CEHJ

but wont that restrict me to having to have the estimated time that it will take to transfer the file?
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LVL 86

Expert Comment

by:CEHJ
ID: 9630239
No - it's nothing to do with time - the sleep is just to simulate a lengthy process so you can see the numbers change
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Accepted Solution

by:
CEHJ earned 150 total points
ID: 9630383
Here's a full demo:

public class TestPercent {

      public static void main(String[] args) throws Exception {
            PercentageDisplayer pd = new PercentageDisplayer(500);
            for(int i = 1;i <= 5;i++) {
                  pd.update(100);
                  Thread.sleep(500);
            }
      }

      static class PercentageDisplayer {
            long extent;
            long received;

            public PercentageDisplayer(long extent) {
                  this.extent = extent;
            }

            public void update(long increment) {
                  for(int i = 0;i < 12;i++) {
                        System.out.print('\010');
                  }
                  received += increment;
                  long percentage = 100 * received / extent;
                  System.out.print("" + percentage + "% received");
            }
      }
}
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