Просмотр исходного текста страницы C/File/File Pointer

==Reposition file pointer to a saved location: how to use fsetpos==


   
<source lang="cpp">

#include <stdio.h>
int main ()
{
  FILE * file;
  fpos_t pos;
  file = fopen ("my.txt", "w");
  
  fgetpos(file, &pos);
  
  fputs ("That is a line." ,file);
  
  fsetpos (file, &pos);
  fputs ("This", file);
  
  fclose (file);
  return 0;
}
           
       </source>


==Reset file position indicator to                   start of the file==


   
<source lang="cpp">
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
  char str[80];
  FILE *fp;
  if((fp = fopen("TEST", "w+"))==NULL) {
    printf("Cannot open file.\n");
    exit(1);
  }
  do {
    printf("Enter a string (CR to quit):\n");
    gets(str);
    strcat(str, "\n");  /* add a newline */
    fputs(str, fp);
  } while(*str!="\n");
  rewind(fp);  /* reset file position indicator to
                  start of the file. */
  while(!feof(fp)) {
    fgets(str, 79, fp);
    printf(str);
  }
  return 0;
}
           
       </source>


== Return the current position in a stream: how to use ftell==


   
<source lang="cpp">

#include <stdio.h>
int main ()
{
  FILE *file;
  long size;
  file = fopen ("my.txt","rb");
  
  if (file == NULL) 
      perror ("Error reading my.txt.");
  else {
    fseek (file, 0, SEEK_END);
    size = ftell(file);
    
    fclose (file);
    printf ("Size of my.txt is %ld bytes.\n",size);
  }
  return 0;
}

           
       </source>


==Set the file pointer to the beginning of a stream: how to use rewind==


   
<source lang="cpp">

#include <stdio.h>
int main ()
{
  int n;
  FILE *file;
  char buffer[27];
  file = fopen ("my.txt", "w+");
  
  for ( n="A" ; n<="Z" ; n++)
    fputc ( n, file);
  
  rewind ( file );
  fread (buffer, 1, 26, file);
  fclose ( file );
  buffer[26] = "\0";
  puts ( buffer );
  
  return 0;
}
           
       </source>