1.1 列出一个目录中的所有文件

#include "apue.h"
#include <dirent.h>
int
main(int argc, char *argv[])
{
DIR            *dp;
struct dirent    *dirp;
if (argc != 2)
err_quit("usage: ls directory_name");
if ((dp = opendir(argv[1])) == NULL)
err_sys("can't open %s", argv[1]);
while ((dirp = readdir(dp)) != NULL)
printf("%s\n", dirp->d_name);
closedir(dp);
exit(0);
}