C语言写个输出文件大小的程序

Question

Write a C program that takes a single file name as a parameter and
outputs to standard output the size of the file in bytes. You may assume the file
exists and it is just a regular file. Place your answer in the file called 'mysize.c' in the
Q3 directory. (hint - “man 2 stat”) When run from the command line you should see :
$ ./mysize 100bytefile
100
$ ./mysize emptyfile
0

Answer 1

#include <stdio.h>
#include <sys/stat.h>

int main(int ac, char * av[]) {
  struct stat sb;
  stat(av[1], &sb);
  printf("%lld\n", (long long) sb.st_size);
  return 0;
}

Answer 2

像楼上的，打开一个文件，fseek函数把文件位置移动到末端，然后ftell获取文件当然位置并返回就是文件大小了，

Answer 3

//mysize.c

#include <stdio.h>
int main(int argc, char* argv[])
{
long int iFileLen;
FILE *pFile;
if(argc==1){
printf("usage: mysize <filename>\n");
return 0;}

pFile = fopen( argv[1], "rb" );
if ( pFile == NULL ) {
printf("file not found\n");
return 1;}

fseek( pFile, 0, SEEK_END );
iFileLen = ftell( pFile );

fclose( pFile );
printf("%ld\n",iFileLen);
return 0;
}