实现stat命令

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(int argc,char* argv[])
{
	if(argc<2)
	{
		printf("./mystat filename\n");
		exit(1);
	}
	// 文件信息结构体
	struct stat st;
	
	int ret = stat(argv[1],&st);
	if(ret == -1)
	{
		perror("stat");
		exit(1);
	}
	
	
	//存储文件类型和访问权限
	char perms[11] = { 0 };
	//判断文件类型
	switch(st.st_mode & S_IFMT)
	{
		case S_IFLNK:
			perms[0] = 'l';
			break;
		case S_IFDIR:
			perms[0] = 'd';
			break;
		case S_IFREG:
			perms[0] = '-';
			break;
		case S_IFBLK:
			perms[0] = 'b';
			break;
		case S_IFSOCK:
			perms[0] = 's';
			break;
		case S_IFIFO:
			perms[0] = 'f';
			break;
		default:
			perms[0] = '?';
			break;
		}
		
		//判断文件的访问属性
		//文件所有者
		perms[1] = (st.st_mode & S_IRUSR) ? 'r':'-';
		perms[2] = (st.st_mode & S_IWUSR) ? 'w':'-';
		perms[3] = (st.st_mode & S_IXUSR) ? 'x':'-';
			
		//判断所有组
		perms[4] = (st.st_mode & S_IRGRP) ? 'r':'-';
		perms[5] = (st.st_mode & S_IWGRP) ? 'w':'-';
		perms[6] = (st.st_mode & S_IXGRP) ? 'x':'-';
			
		//判断其他人
		perms[7] = (st.st_mode & S_IROTH) ? 'r':'-';
		perms[8] = (st.st_mode & S_IWOTH) ? 'w':'-';
		perms[9] = (st.st_mode & S_IXOTH) ? 'x':'-';
			
		//硬链接计数
		int linkNum = st.st_nlink;
		//文件所有者
		char* fileUser = getpwuid(st.st_uid)->pw_name;
		//文件所属组
		char* fileGrp = getgrgid(st.st_gid)->gr_name;
		//文件大小
		int fileSize = st.st_size;
		//修改时间
		char* time = ctime(&st.st_mtime);
		char mtime[512] = {0};
		strncpy(mtime,time,strlen(time)-1);
		
		char buf[1024];
		
		sprintf(buf,"%s %d %s %s %d %s %s %s",perms,linkNum,fileUser,fileGrp,fileSize,mtime,argv[1]);
		
		printf("%s\n",buf);
		return 0;
		
}