Can't creat as many files as need in a folder

Hello friends,

I hope there are some expert in Filestream programming with C.
First of all, sorry for my english. I'm not native english speaker.

I'm making some experiment with File streaming in C. In all the cases, until in the following one, the programs works as expected. But surprising, here not.

What is the program about?

I tried to write a program which creates as many files as needed in a folder. The name of the file does not change. Only the number of the file increase after every iteration by 1.

The program works prefect and as supposed, until (at arround) 500 files are created. After this, the program continues working without any problem, but no one new file is created in the folder.

I'm wondering why this happens. I took a look in Internet and it seems to me that the problem is not the OS. So I think it could be a problem with the buffer. But still cleaning the buffer does not helps.

Here the code:

Code:

---

#include <stdio.h>

int main(void)
{
  unsigned int i = 0, count = 1;

  // Max iteretions
  const unsigned int MAX = 520;

  unsigned char index_file_name = '0';

  // Datafile name and place
  char datafile_name[] = "many_files/datafile_name_00000.txt";

  FILE *file_pointer_datafile = NULL;

  //printf("Cantidad de vueltas> %i\n", MAX+1);
#define INDEX 29
  printf("Program starts...\n");

  // Loop is created with goto
while_GLOBAL:

  // The new Filename is changed increasing the number by one
  // So, first created file is named:
  // datafile_name_00001.txt
  // The next one
  // datafile_name_00002.txt
  // and so on.
  if (index_file_name != '0') {

    datafile_name[INDEX] = index_file_name;
  }

  else if (index_file_name == '0')
  {
    i = 0;
    while (datafile_name[INDEX - i] == '9') {

      datafile_name[INDEX - i] = '0';

      i++;
    }
    datafile_name[INDEX - i] += 1;
  }
  // Creats the realtion between filepointer and new name of file.
  file_pointer_datafile = fopen(datafile_name, "w+");
  //printf("%i\n", index_file_name-48);

  // Interrps the goto-loop when count is equal to MAX
  if (count <= MAX) {

    count++;
    index_file_name++;
    if (index_file_name > 57) {

      index_file_name = '0';
    }
    //printf("%i\n", count);
    goto while_GLOBAL;

  } else {

    printf("Programa finaliza...");
    goto while_FIN;
  }
  // Hear I am trying to clean any posible buffer
  fflush(stdin);
  fflush(stdout);
  fflush(file_pointer_datafile);
  // Relation between filepointer and file is closed
  fclose(file_pointer_datafile);
  goto while_GLOBAL;


  // End of program
while_FIN:

  return 0;
}

---

What is happening? What I'm doing wrong?

Thanks for any good idea!
Gisi

Here's where 'goto' is not your friend

Code:

---

// Interrps the goto-loop when count is equal to MAX
if(count<=MAX) {

        count++; index_file_name++; if(index_file_name>57) {

index_file_name='0';

}

//printf("%i\n", count);
goto while_GLOBAL;

  }

---

Where you "goto while_GLOBAL", you're not closing the file.

Your process is running out of file handles.

I'd suggest something like:

Code:

---

while( count <= MAX )
{
 // do whatever creates index_file_name


 // Creats the realtion between filepointer and new name of file.
 file_pointer_datafile=fopen(datafile_name, "w+");

 count++;
 index_file_name++;

 if(index_file_name>57)
 {
  index_file_name='0';
 }


 // Hear I am trying to clean any posible buffer
 fflush(stdin);
 fflush(stdout);
 fflush(file_pointer_datafile);
 // Relation between filepointer and file is closed
 fclose(file_pointer_datafile);

}

// output finished, close program

---

Thank you! You give me the way to find the solution! It was not much to modify.

You are right, goto is really not easy to handle.
But in this case, I need to use goto. goto is much far away faster than while, for or do-while.
So I need to find a solution with goto...

Here the code with the correction you helped me to do:

Code:

---

#include <stdio.h>

int main(void)
{
    unsigned int
        i=0, count=1;

    // Max iteretions
    const unsigned int MAX=520;

    unsigned char
        index_file_name='0';

    // Datafile name and place
    char  datafile_name[]="many_files/datafile_name_00000.txt";

    FILE* file_pointer_datafile=NULL;

        //printf("Cantidad de vueltas> %i\n", MAX+1);
    #define INDEX 29
        printf("Program starts...\n");

        // Loop is created with goto
        while_GLOBAL:

        // The new Filename is changed increasing the number by one
        // So, first created file is named:
        // datafile_name_00001.txt
        // The next one
        // datafile_name_00002.txt
        // and so on.
        if(index_file_name!='0')
        {
            datafile_name[INDEX]=index_file_name;
        }
        else if(index_file_name=='0')
        {
            i=0;
            while(datafile_name[INDEX-i]=='9')
            {
                datafile_name[INDEX-i]='0';
                i++;
            }
            datafile_name[INDEX-i]+=1;
        }

        // Creats the realtion between filepointer and new name of file.
        file_pointer_datafile=fopen(datafile_name, "w+");
        //printf("%i\n", index_file_name-48);

        // Interrps the goto-loop when count is equal to MAX
        if(count<=MAX)
        {
            count++;
            index_file_name++;
            if(index_file_name>57)
            {
                index_file_name='0';
            }
            //printf("%i\n", count);
            fflush(stdin);
            fflush(stdout);
            fflush(file_pointer_datafile);
            // Relation between filepointer and file is closed
            fclose(file_pointer_datafile);
            goto while_GLOBAL;
        }
        else
        {
            printf("Programa finaliza...");
            goto while_FIN;
        }
        // Hear I am trying to clean any posible buffer

        goto while_GLOBAL;

        // End of prgram
while_FIN:

            fflush(stdin);
            fflush(stdout);
            fflush(file_pointer_datafile);
            // Relation between filepointer and file is closed
            fclose(file_pointer_datafile);

return 0;

}

---

Thank you very much!!
Gisi

> But in this case, I need to use goto. goto is much far away faster than while, for or do-while.
Rubbish.

It wasn't faster because you spent HOURS chasing a problem that had no business being created.

Sorry, I think I didn't express my idea well enough. I didn't mean that goto is faster by creating a program.

What I mean is that a program written with goto instead of while, for or do-while, is much faster.
In my case it is not important how long I need to write a program with goto.
The resulting program itself, not the time it is need to create it, has to be so fast as possible.
This is the reason why I needed to find a solution with goto and not with while, for or do-while.

I hope, I could explain my idea this time better!

Thank you again!

After 40+ years of writing in C and C++, I can tell you that you've been given incorrect information about the speed of goto vs while, for or do-while. Factually, there is either no difference at all whatsoever, or there is only that difference you might think you can measure. When you examine the assembler produced by both results, you'll realize it CAN'T be any faster. There's just nothing "there" to be faster.

Seriously, examine the matter from an engineer's perspective and test it under stress. Look at the underyling assembler.

Aside from that, it can't impact the performance of this code because by far the time consuming component is the system calls to create the file, not the loop.

I think this discussion not part of the problem I asked for, so I said good by and thanks again! :-D

> The resulting program itself, not the time it is need to create it, has to be so fast as possible.
The moment you opened a file, all sense of "+/- a few nanoseconds" went out the window.

You're instantly comparing the nanoseconds of an instruction with the milliseconds it takes to move the head of your hard disk.
That's easily in the order of 1E6 to 1E7 times slower.

Besides, if you really cared about 'goto is better than while', you would have applied it to your INNERMOST loop first.
> while(datafile_name[INDEX-i]=='9')

If it needs to be that fast, you should probably consider writing it in assembly :)

As a side note...
Why fflush(stdin) is wrong - Cprogramming.com