C library function - fgetpos()

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Description

The C library function int fgetpos(FILE *stream, fpos_t *pos) gets the current file position of the stream and writes it to pos.

Declaration

Following is the declaration for fgetpos() function.

int fgetpos(FILE *stream, fpos_t *pos)

Parameters

  • stream -- This is the pointer to a FILE object that identifies the stream.

  • pos -- This is the pointer to a fpos_t object.

Return Value

This function returns returns zero on success, else non-zero value in case of error.

Example

The following example shows the usage of fgetpos() function.

#include <stdio.h>

int main ()
{
   FILE *fp;
   fpos_t position;

   fp = fopen("file.txt","w+");
   fgetpos(fp, &position);
   fputs("Hello, World!", fp);
  
   fsetpos(fp, &position);
   fputs("This is going to override previous content", fp);
   fclose(fp);
   
   return(0);
}

Let us compile and run the above program, this will create a file file.txt which will have the following content. First of all we get the initial position of the file using fgetpos() function and then we write Hello, World! in the file but later we used fsetpos() function to reset the write pointer at the begining of the file and then over-write the file with the following content:

This is going to override previous content

Now let's the content of the above file using the following program:

#include <stdio.h>

int main ()
{
   FILE *fp;
   int c;
   int n = 0;

   fp = fopen("file.txt","r");
   while(1)
   {
      c = fgetc(fp);
      if( feof(fp) )
      {
          break ;
      }
      printf("%c", c);
   }

   fclose(fp);

   return(0);
}


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