函数名: fseek 
 功  能: 重定位流上的文件指针 
 用  法: #include <stdio.h>
         int fseek(FILE *stream, long offset, int fromwhere); 
 程序例: 
#include <stdio.h>
long filesize(FILE *stream);
int main(void) 
 { 
    FILE *stream; 
   stream = fopen("MYFILE.TXT", "w+"); 
    fprintf(stream, "This is a test"); 
    printf("Filesize of MYFILE.TXT is %ld bytes\n", filesize(stream)); 
    fclose(stream); 
    return 0; 
 } 
long filesize(FILE *stream) 
 { 
    long curpos, length; 
   curpos = ftell(stream); 
    fseek(stream, 0L, SEEK_END); 
    length = ftell(stream); 
    fseek(stream, curpos, SEEK_SET); 
    return length; 
 }