Linux 文件IO-目录操作

文件IO 目录操作

1. 打开目录 opendir()

#include <sys/types.h>
#include <dirent.h>			//directory entry -- 目录项
DIR *opendir(const char *name);

返回值:
	成功返回目录流指针,失败返回NULL;
参数:
	name:	要打开的目录名

#include <sys/types.h>
#include <dirent.h>
int closedir(DIR *dirp);

参数:
	dirp:	目录流指针
返回值:
	成功返回 0, 失败返回 -1;

2. 创建目录 mkdir()

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

int mkdir(const char *pathname, mode_t mode);
返回值:
	成功返回 0, 失败返回 -1
参数:
	pathname: 要创建目录名
    mode:	赋予权限

3. 读取目录 readdir()

readdir 一次只能随机读取一个目录项

#include <dirent.h>
struct dirent *readdir(DIR *dirp);

返回值:
	成功返回结构体指针, 失败返回 NULL;
参数:	
	dirp:	目录流指针
        
struct dirent{
    ......
	char	d_name[256]; /* 文件名 */
};

4. 关闭目录 closedir()

#include <sys/types.h>
#include <dirent.h>
int closedir(DIR *dirp);

返回值:
	成功返回 0, 失败返回 -1;
参数:
	dirp:	目录流指针

5. 获取文件属性 – lstat

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

/* 不能查链接文件除了文件名的其他信息
int stat(const char *pathname, struct stat *statbuf);
*/
//int fstat(int fd, struct stat *statbuf);
int lstat(const char *pathname, struct stat *statbuf);
返回值:
	成功返回 0, 失败返回 -1;
参数:
	pathname:	文件名
    statbuf:	结构体指针

struct stat {
	dev_t     st_dev;         /* ID of device containing file */
	ino_t     st_ino;         /* Inode number */
	mode_t    st_mode;        /* File type and mode 文件类型和权限*/
	nlink_t   st_nlink;       /* Number of hard links 硬链接数*/
	uid_t     st_uid;         /* User ID of owner 用户ID*/
	gid_t     st_gid;         /* Group ID of owner 组ID*/
	dev_t     st_rdev;        /* Device ID (if special file) */
	off_t     st_size;        /* Total size, in bytes 文件大小字节为单位*/
	blksize_t st_blksize;     /* Block size for filesystem I/O */
	blkcnt_t  st_blocks;      /* Number of 512B blocks allocated */
    
	struct timespec st_atim;  /* Time of last access */
	struct timespec st_mtim;  /* Time of last modification 最后一次修改文件		时间*/
	struct timespec st_ctim;  /* Time of last status change */

#define st_atime st_atim.tv_sec      /* Backward compatibility 向后兼容*/
#define st_mtime st_mtim.tv_sec
#define st_ctime st_ctim.tv_sec
};

//st_mode 相关

//获取文件类型 若 st_mode & s_IFMT等于对应文件类型宏,文件类型宏对应文件类型
S_IFMT     0170000   bit mask for the file type bit field
    
S_IFSOCK   0140000   socket
S_IFLNK    0120000   symbolic link
S_IFREG    0100000   regular file
S_IFBLK    0060000   block device
S_IFDIR    0040000   directory
S_IFCHR    0020000   character device
S_IFIFO    0010000   FIFO
	eg.
    struct stat *sb;
    lstat(pathname, &sb);
           if ((sb.st_mode & S_IFMT) == S_IFREG) {//是普通文件
      	   }

//若st_mode & 对应权限宏 == 宏本身,表示具有该权限
S_IRWXU     00700   owner has read, write, and execute permission
S_IRUSR     00400   owner has read permission
S_IWUSR     00200   owner has write permission】
S_IXUSR     00100   owner has execute permission

S_IRWXG     00070   group has read, write, and execute permission
S_IRGRP     00040   group has read permission
S_IWGRP     00020   group has write permission
S_IXGRP     00010   group has execute permission

S_IRWXO     00007   others (not in group) have read,  write,  and
                               execute permission
S_IROTH     00004   others have read permission
S_IWOTH     00002   others have write permission
S_IXOTH     00001   others have execute permission
    eg.
    if(sb.st_mode & S_IRWXU)//有用户读写执行权限
        

获取用户信息和组信息：

#include <sys/types.h>
#include <pwd.h>
struct passwd *getpwuid(uid_t uid);//根据用户id获取用户信息

struct passwd {
	char   *pw_name;       /* username */
	char   *pw_passwd;     /* user password */
	uid_t   pw_uid;        /* user ID */
	gid_t   pw_gid;        /* group ID */
	char   *pw_gecos;      /* user information */
	char   *pw_dir;        /* home directory */
	char   *pw_shell;      /* shell program */
};

#include <sys/types.h>
#include <grp.h>
struct group *getgrgid(gid_t gid);//根据组id获取组信息

struct group {
    char   *gr_name;        /* group name */
    char   *gr_passwd;      /* group password */
    gid_t   gr_gid;         /* group ID */
	......
};