Thread: code help

1. Main always returns int
2. Your FILE pointer should be assigned NULL before it's used if not assigned at declaration
3. It's also a good idea to assign the struct member "number" something also before it's read by scanf. Then there is no risk of over writing a possible garbage value.
4. Update your compiler to at least a C99 compliant one if possible. (code::blocks) is one of the best IDE's for C and has a variety of options for compilers.

As already mentioned, pick an indent style and stick to it.

Here, for your delectation, courtesy of indent -kr -nut -ts2 -i2 -l120 -cli0 foo.c

Code:

#include<stdio.h>
#include<stdlib.h>
#include<assert.h>

struct consumer {
  int number;
  int n;
};

main()
{
  int count, i, f1;
  count = 0;
  char c;
  float charge, fee;
  struct consumer consumer, fileconsumer;
  consumer.n = -1;
  printf("give me the number of the charge \n");
  fflush(stdin);
  scanf("%f", &charge);
  FILE *fp;

  while (1) {
    f1 = 0;
    scanf("%s", &c);
    if (c == '0')
      break;
    printf("give me the number of the calling cellphone ");
    scanf("%d", &consumer.number);
    fp = fopen("consumer.txt", "+ab");
    assert(fp == NULL);
    for (i = 0; i < count; i++) {
      rewind(fp);
      fseek(fp, sizeof(struct consumer) * i, SEEK_SET);
      fread(&fileconsumer, sizeof(struct consumer), 1, fp);
      if (consumer.number == fileconsumer.number) {
        fileconsumer.n++;
        rewind(fp);
        fseek(fp, sizeof(struct consumer) * i, SEEK_SET);
        fwrite(&fileconsumer, sizeof(struct consumer), 1, fp);
        f1 = 1;
        break;
      }
    }
    if (!f1) {
      consumer.n++;
      rewind(fp);
      fseek(fp, sizeof(struct consumer) * count, SEEK_SET);
      fwrite(&consumer, sizeof(struct consumer), 1, fp);
      fclose(fp);
      count++;
    }
  }

  fp = fopen("consumer.txt", "+ab");
  assert(fp == NULL);
  for (i = 0; i < count; i++) {
    fseek(fp, sizeof(struct consumer) * i, SEEK_SET);
    fread(&fileconsumer, sizeof(struct consumer), 1, fp);
    if (fileconsumer.n == 0) {
      rewind(fp);
      fseek(fp, sizeof(struct consumer) * count, SEEK_SET);
      fread(&fileconsumer, sizeof(struct consumer), 1, fp);
      rewind(fp);
      fseek(fp, sizeof(struct consumer) * (count - i), SEEK_END);
      fwrite(&fileconsumer, sizeof(struct consumer), 1, fp);
      count--;
    }
  }
  
  for (i = 0; i < count; i++) {
    rewind(fp);
    fseek(fp, sizeof(struct consumer) * i, SEEK_SET);
    fread(&fileconsumer, sizeof(struct consumer) * i, 1, fp);
    if (fileconsumer.n >= 10) {
      fee = charge * fileconsumer.n;
      fee = charge * fileconsumer.n - charge * fileconsumer.n / 10;
      printf("the charge for the number %d it is %f \n", fileconsumer.number, fee);
    } else {
      fee = charge * fileconsumer.n;
      printf("the charge for the number %d it is %f \n ", fileconsumer.number, fee);
    }
    fileconsumer.n = 0;
    fseek(fp, sizeof(struct consumer) * i, SEEK_SET);
    fwrite(&fileconsumer, sizeof(struct consumer) * i, 1, fp);
  }

  fclose(fp);
}

Regarding the fopen mode:

Originally Posted by C99

The argument mode points to a string. If the string is one of the following, the file is
open in the indicated mode. Otherwise, the behavior is undefined. 214)
r
open text file for reading
w
truncate to zero length or create text file for writing
a
append; open or create text file for writing at end-of-file
rb
open binary file for reading
wb
truncate to zero length or create binary file for writing
ab
append; open or create binary file for writing at end-of-file
r+
open text file for update (reading and writing)
w+
truncate to zero length or create text file for update
a+
append; open or create text file for update, writing at end-of-file
r+b or rb+ open binary file for update (reading and writing)
w+b or wb+ truncate to zero length or create binary file for update
a+b or ab+ append; open or create binary file for update, writing at end-of-file

Regarding your use of 'a' mode.

Originally Posted by c99

Opening a file with append mode (’a’ as the first character in the mode argument)
causes all subsequent writes to the file to be forced to the then current end-of-file,
regardless of intervening calls to the fseek function. In some implementations, opening
a binary file with append mode (’b’ as the second or third character in the above list of
mode argument values) may initially position the file position indicator for the stream
beyond the last data written, because of null character padding.

This nullifies your attempt to try and update records in place using fseek calls.

> if (!f1)
If a few lines earlier, you did f1=1, then there is no call to fclose() in this iteration of the while(1) loop. As a result, you end up with multiple open file handles, with no way to close them.

> if (fileconsumer.n == 0)
Perhaps you could explain in words what you think this code is doing.
You seem to be trying to overwrite a 'deleted' record with a record from the end of the file. But you don't seem to do these things
- actually delete the last record (which you now have a copy of)
- actually check whether the moved record is one that should have been deleted anyway.

Further, I think your fseek offset to SEEK_END should be negative, not positive.

In general, your variable names could be a lot better. Names like 'count' and 'n' are far to general to convey any useful meaning.

I would also suggest you remove the code which tries to compact the file until you have something basic working.