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Jakejake

07-18-2005 10:52 AM

[C] Incremental string updates - 00001.png 00002.png etc

Hi,
I am writing a program in C that will be outputting a lot of files that I want to be named 00001.png 00002.png 00003.png and so on.

The way I am doing it at the moment is as follows:

Code:

        for(i=0; i < 10000; i++)

        {

                filename[4]++;

                if(filename[4] > 57)

                {

                        filename[4] = 48;

                        filename[3]++;

                        if(filename[3] > 57)

                        {

                                filename[3] = 48;

                                filename[2]++;

                                if(filename[2] > 57)

                                {

                                        filename[2] = 48;

                                        filename[1]++;

                                        if(filename[1] > 57)

                                        {

                                                filename[1]++;

                                        }

                                }

                        }

                }

                //CODE THAT WRITES TO FILE USING filename

        }

Now this seems a rather ugly way to do it. What I should be doing is simply incrementing an integer and then converting that to a string somehow, but I can't work out how to do this.

Any ideas?

Thanks

Robbie

hrdwareguy

07-18-2005 12:18 PM

You could do something like this:

Code:

string:filename;

for i=1 to 10000

{

  filename=IntToStr(i)+.PNG;

  while length(filename) < 12 filename='0'+filename;

  //write file here

}

where 12 is whatever lenght you want to give the filename including the .PNG extension.

feelgood

07-18-2005 12:27 PM

Never mind, was thinking in Java, not C

Anomaly_

07-18-2005 12:42 PM

In C you could do something like this:

Code:

int num = 0;

char fileName[5];

  

int i;

for(i = 0; i <= 10000; i++)

{

  sprintf(fileName, "%05d", num);

  // Append file extension to fileName and write it

  num++;                

}

billys

07-18-2005 12:43 PM

My C is a bit rusty but sprintf is your friend here.

Try:

Code:

char buffer[10];

for(int i=0; i<10000; i++) {

  sprintf(buffer, "%05d.png", i);

  /* write file contents */

}

the %05d is a format string that tells the compiler to format a string containing a decimal integer (the d) to a width of 5 characters (the 5) and to pad using a 0 character (the 0) and then to append that with .png.

I dont have a C compiler anymore so I cant test this but it should be right, google will find you literally hundreds of guides to format strings with printf and sprintf though.

Hope this helps

billys

07-18-2005 12:45 PM

beaten by a minute :) I guess it confirms that the %05d was right though, i wasnt sure :)

Jakejake

07-18-2005 01:19 PM

Thanks guys. The sprintf() command worked great.

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