fgetpos

    int fgetpos(FILE *stream, fpos_t *pos);

Stores current file position for stream stream in *pos. Returns non-zero on error.

The fgetpos() function stores the file position indicator of the given file stream in the given position variable.
The position variable is of type fpos_t (which is defined in stdio.h) and is an object that can hold every possible position in a FILE.
fgetpos() returns zero upon success, and a non-zero value upon failure.

/* 
 * fgetpos example code
 * http://code-reference.com/c/stdio.h/fgetpos
 */
 
 
#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */
 
 
int main( void )
{
    FILE *stream;
    fpos_t file_pos;
    int c,i;
 
    if((stream=fopen("test.txt","r"))==NULL) {
        printf("Cannot open file.\n");
        return 1;
      }
 
    fgetpos(stream, &file_pos); 
    while((c = fgetc(stream) ) != EOF) {
     if ( c == '#' ){ 
             fgetpos(stream, &file_pos); 
           }
 
        printf("character is:  %c\n", c);
     }
 
      printf("1st Position of # is the %d Byte\n", file_pos);
      fclose(stream);
 
return 0;
}

  output: ./fgetpos 
  character is:  L
  character is:  i
  character is:  n
  character is:  e
  character is:   
  character is:  1
  character is:  
  character is:  #
  .... and so on
  ...
  1st Position of # is the 24 Byte