Linux笔记：使用stat函数实现ls -l的功能（getpwuid函数 getgrgid函数使用）

stat函数：获取文件信息

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

int stat(const char *pathname, struct stat *buf);
struct stat {
    
    
               dev_t     st_dev;         /* ID of device containing file */
               ino_t     st_ino;         /* inode number */
               mode_t    st_mode;        /* protection */
               nlink_t   st_nlink;       /* number of hard links */
               uid_t     st_uid;         /* user ID of owner */
               gid_t     st_gid;         /* group ID of owner */
               dev_t     st_rdev;        /* device ID (if special file) */
               off_t     st_size;        /* total size, in bytes */
               blksize_t st_blksize;     /* blocksize for filesystem I/O */
               blkcnt_t  st_blocks;      /* number of 512B blocks allocated */
               }

getpwuid函数：解码所有者信息（解析struct stat中的st_uid数据）

#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 */
           };

getgrgid函数：解码所属组信息（解析struct stat中的 st_gid数据）

#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 */
           };

localtime函数：解码上次访问时间信息 （解析struct stat中的 st_atime数据）

#include <time.h>
struct tm *localtime(const time_t *timep);
struct tm {
    
    
               int tm_sec;    /* Seconds (0-60) */
               int tm_min;    /* Minutes (0-59) */
               int tm_hour;   /* Hours (0-23) */
               int tm_mday;   /* Day of the month (1-31) */
               int tm_mon;    /* Month (0-11) */
               int tm_year;   /* Year - 1900 */
               int tm_wday;   /* Day of the week (0-6, Sunday = 0) */
               int tm_yday;   /* Day in the year (0-365, 1 Jan = 0) */
               int tm_isdst;  /* Daylight saving time */
           };

使用stat函数实现ls -l的功能例程：

//使用stat函数实现ls -l的功能
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
#include <pwd.h>
#include <grp.h>

int  main(int argc,const char * argv[])
{
    
    
	struct stat info;
	stat(argv[1],&info);
	//打印类型，权限
	switch(info.st_mode & S_IFMT)
	{
    
    
		case S_IFREG:printf("-");break;
		case S_IFDIR:printf("d");break;
		case S_IFLNK:printf("l");break;
		case S_IFCHR:printf("c");break;
		case S_IFBLK:printf("b");break;
		case S_IFIFO:printf("p");break;
		case S_IFSOCK:printf("s");break;
	}
	char rwx[]={
    
    'r','w','x'};
	for(int i=0; i<10; i++)
	{
    
    
		printf("%c",info.st_mode & (0400>>i) ? rwx[i%3] : '-');
	}
	//打印所有者，所属组 
	struct passwd *pswd;
	pswd=getpwuid(info.st_uid);
	printf(" %s",pswd->pw_name);
	
	struct  group  *grp;
	grp=getgrgid(info.st_gid);
	printf(" %s",grp->gr_name);
	
	//打印文件大小
	printf(" %ld ",info.st_size);
	//打印最近时间 
	struct tm *atime;
	atime = localtime(&info.st_mtime);
	printf("%d-%d-%d %d:%d "
		,atime->tm_year+1900
		,atime->tm_mon+1,atime->tm_mday
		,atime->tm_hour,atime->tm_min);
	//打印文件名
	printf(" %s\n",argv[1]);
	
	return 0;
}

编译运行 ：