ls.c

linux下ls的简单实现

/*实现ls -l -a*/
#include <unistd.h>
#include <stdio.h>
#include <dirent.h>
#include <time.h>
#include <string.h>
#include <sys/stat.h>
#include <stdlib.h>

#include <pwd.h>
#include <grp.h>

/*获取用户名*/
char *uid_to_name(uid_t uid)
{
	struct passwd  *pw_ptr;
	static char numstr[10];

	if( (pw_ptr = getpwuid(uid)) == NULL)
	{
		printf(numstr, "%d", uid);
		return numstr;
	}
	else
		return pw_ptr->pw_name;
}

/*获取用户组名*/
char *gid_to_name(gid_t gid)
{
	struct group *grp_ptr;
	static char numstr[10];

	if ((grp_ptr = getgrgid(gid)) == NULL)
	{
		sprintf(numstr, "%d", gid);
		return numstr;
	}
	else
		return grp_ptr->gr_name;
}

/*获取文件夹或文件的权限*/
int get_purview(int mode,char *purview)
{
	strcpy(purview, "----------");
    
	if(S_ISDIR(mode)) purview[0] = 'd';
	if(S_ISCHR(mode)) purview[0] = 'c';
	if(S_ISBLK(mode)) purview[0] = 'b';
    
	if(mode & S_IRUSR) purview[1] = 'r';
	if(mode & S_IWUSR) purview[2] = 'w';
	if(mode & S_IXUSR) purview[3] = 'x';
   
	if(mode & S_IRGRP) purview[4] = 'r';
	if(mode & S_IWGRP) purview[5] = 'w';
	if(mode & S_IXGRP) purview[6] = 'x';
   
	if(mode & S_IROTH) purview[7] = 'r';
	if(mode & S_IWOTH) purview[8] = 'w';
	if(mode & S_IXOTH) purview[9] = 'x'; 
}

/*显示ls -l的内容*/
int show_ls(char *filename,struct stat *statbuf)
{
	char purview[11] = {0};
	get_purview(statbuf->st_mode,purview);

	printf("%s",purview);//文件权限
	printf("%5d ",statbuf->st_nlink);//文件的硬链接数目
	printf("%-8s",uid_to_name(statbuf->st_uid));//文件拥有者的名称
	printf("%-8s",gid_to_name(statbuf->st_gid));//文件的组名称
	printf("%8ld ",(long)statbuf->st_size);//文件的大小
	printf("%.12s ",4+ctime(&statbuf->st_mtime));//文件的修改时间
	printf("%s\n", filename);//文件名
}

/*读取目录*/
void  printdir(char *dir)
{
	DIR *dp;
	struct dirent *entry;
	struct stat statbuf;
	
	char buf[1024];//存放当前路径
	if (getcwd(buf,sizeof(buf)) == NULL)
	{
		exit(1);
	}
	if ((dp = opendir(dir)) == NULL)
	{
		fprintf(stderr,"can not open directory: %s\n",dir);
		return ;
	}
	chdir(dir);
	while ((entry = readdir(dp)) != NULL)
	{
		lstat(entry->d_name,&statbuf);
		if (strcmp(".",entry->d_name) == 0 
			|| strcmp("..",entry->d_name) == 0
			|| entry->d_name[0] == '.')
			continue;
		show_ls(entry->d_name,&statbuf);
	}
	chdir(buf);//还原路径
	closedir(dp);
}

/*主函数*/
int main(int argc,char *argv[])
{
	int i;
	if (argc == 1)
	{
		printdir(".");
		return 0;
	}
	for (i=1; i<argc; i++)
	{
		printf("%s:\n",argv[i]);
		printdir(argv[i]);
		printf("\n\n");
	}
	return 0;
}