用fseek和ftell获取文件的大小

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main(int argc,char *argv[])
{
int n=0;
FILE *fp;
if((fp=fopen(argv[1],"r"))==NULL)
{
perror("fopen");
exit(EXIT_FAILURE);
}
if(fseek(fp,0,SEEK_END)!=0)
{
perror("fseek");
exit(EXIT_FAILURE);
}
if((n=ftell(fp))==-1)
{
perror("ftell");
exit(EXIT_FAILURE);
}
printf("the size counted by fseek/ftell of the file is %d \n",n);
printf("this is ls output:\n");
execl("/bin/ls","ls","-l",argv[1],(char *)0);
fclose(fp);
}