函数名: fsetpos 
 功  能: 定位流上的文件指针 
 用  法: #include <stdio.h>
         int fsetpos(FILE *stream, const fpos_t *pos); 
 程序例: 
#include <stdlib.h> 
 #include <stdio.h> 
void showpos(FILE *stream);
int main(void) 
 { 
    FILE *stream; 
    fpos_t filepos; 
   /* open a file for update */ 
    stream = fopen("DUMMY.FIL", "w+"); 
   /* save the file pointer position */ 
    fgetpos(stream, &filepos); 
   /* write some data to the file */ 
    fprintf(stream, "This is a test"); 
   /* show the current file position */ 
    showpos(stream); 
   /* set a new file position, display it */ 
    if (fsetpos(stream, &filepos) == 0) 
      showpos(stream); 
    else 
    { 
       fprintf(stderr, "Error setting file \ 
        pointer.\n"); 
       exit(1); 
    } 
   /* close the file */ 
    fclose(stream); 
    return 0; 
 } 
void showpos(FILE *stream) 
 { 
    fpos_t pos; 
   /* display the current file pointer 
       position of a stream */ 
    fgetpos(stream, &pos); 
    printf("File position: %ld\n", pos); 
 }