C语言文件的属性获取

先了解下面的这几个结构体

以下三个函数可以获取文件/目录的属性信息：
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

int stat(const char *path, struct stat *buf);//如果文件是符号链接文件，它会返回该链接文件的源文件
int fstat(int fd, struct stat *buf);//需要先打开文件得到文件描述符
int lstat(const char *path, struct stat *buf);//如果文件是符号链接文件，它会返回链接文件的信息(建议用这个)

struct stat {
dev_t st_dev; /* ID of device containing file 设备文件 /
ino_t st_ino; / Inode number 索引码*/
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 文件拥有者的ID*/
gid_t st_gid; /* Group ID of owner 文件所属组的ID*/
dev_t st_rdev; /* Device ID (if special file) 设备号*/
off_t st_size; /* Total size, in bytes 文件大小*/
blksize_t st_blksize; /* Block size for filesystem I/O 块大小*/
blkcnt_t st_blocks; /* Number of 512B blocks allocated 块数*/
struct timespec st_atim; /* Time of last access 最后访问时间*/
struct timespec st_mtim; /* Time of last modification 最后修改时间*/
struct timespec st_ctim; /* Time of last status change 文件状态最后修改时间*/
}
//通过文件拥有者ID获取用户的属性
#include <sys/types.h>
#include <pwd.h>
struct passwd *getpwuid(uid_t uid);
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 */
};
//通过组ID获取组的信息
#include <sys/types.h>
#include <grp.h>
struct group *getgrgid(gid_t gid);
struct group {
char gr_name; / group name */
char gr_passwd; / group password /
gid_t gr_gid; / group ID */
char *gr_mem; / NULL-terminated array of pointers
to names of group members */
};
可以用以下的宏确定文件类型。这些宏的参数都是struct stat结构中的st_mode成员。
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
S_ISUID 0004000 set UID bit
S_ISGID 0002000 set-group-ID bit (see below)
S_ISVTX 0001000 sticky bit (see below)
S_IRWXU 00700 mask for file owner permissions
S_IRUSR 00400 owner has read permission
S_IWUSR 00200 owner has write permission
S_IXUSR 00100 owner has execute permission
S_IRWXG 00070 mask for group permissions
S_IRGRP 00040 group has read permission
S_IWGRP 00020 group has write permission
S_IXGRP 00010 group has execute permission
S_IRWXO 00007 mask for permissions for others (not in group)
S_IROTH 00004 others have read permission
S_IWOTH 00002 others have write permission
S_IXOTH 00001 others have execute permission

以上就了解一下，下面看代码

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <grp.h>
#include <pwd.h>
#include <time.h>

void Get_file_properties(const char *path)
{
struct stat st;
char *str="xwr-";
int i=0;
char *month[]={"Jan","Feb","Mar","Apr","May","jun","Jul","Aug","Sept","Oct","Nov","Dec"};
if(lstat(path,&st)<0)
{
perror("lstat");
exit(1);
}

///ubuntu 18.04 仿写库函数里面的使用 man 2 stat 指令 往下拉可以看到

switch(st.st_mode & S_IFMT)
{
case S_IFSOCK:printf("socket "); break;
case S_IFLNK :printf("symbolic link "); break;
case S_IFREG :printf("regular file "); break;
case S_IFBLK :printf("block device "); break;
case S_IFDIR :printf("directory "); break;
case S_IFCHR :printf("character device "); break;
case S_IFIFO :printf("FIFO "); break;
case S_ISUID :printf("set UID bit "); break;
case S_ISGID :printf("set-group-ID bit (see below) "); break;
case S_ISVTX :printf("sticky bit (see below) "); break;
case S_IRWXU :printf("mask for file owner permissions "); break;
case S_IRUSR :printf("owner has read permission "); break;
case S_IWUSR :printf("owner has write permission "); break;
case S_IXUSR :printf("owner has execute permission "); break;
case S_IRWXG :printf("mask for group permissions "); break;
case S_IRGRP :printf("group has read permission "); break;
case S_IWGRP :printf("group has write permission "); break;
case S_IXGRP :printf("group has execute permission "); break;
case S_IRWXO :printf("mask for permissions for others(not in group) "); break;
case S_IROTH :printf("others have read permission "); break;
case S_IWOTH :printf("others have write permission "); break;
case S_IXOTH :printf("others have execute permission "); break;
default:printf("unknown "); break;
}
for(i=8;i>=0;i--)
{
if(st.st_mode & 1<< i ) //权限
printf("%c",str[i%3]);
else
printf("%c",str[3]);
}
printf(" %lu ",st.st_nlink);//硬链接数
printf(" %s ",getpwuid(st.st_uid)->pw_name);//通过用户ID得到用户名
printf(" %s ",getgrgid(st.st_gid)->gr_name);//通过所属组ID得到组名
printf("%ld\n",st.st_size);//获取文件大小

struct tm *tp = localtime(&st.st_mtime);
printf("Time of last modification:%s %d ",month[tp->tm_mon],tp->tm_mday);//获取文件修改时间
printf(" %d:%d ",tp->tm_hour,tp->tm_min);
printf(" %d\n",tp->tm_year+1900);
}

int main()
{
Get_file_properties("1.c");

return 0;
}