一、整体大纲
st_mode整体介绍：
st_mode详细介绍：
二、 Linux文件操作相关函数
1. stat
- 作用：获得文件信息，也可以获取文件大小。
- 头文件
#include <sys/types.h> #include <sys/stat.h> #include <unistd.h>
- 函数原型
int stat(const char *path, struct stat *buf); int fstat(int fd, struct stat *buf); int lstat(const char *path, struct stat *buf);
- 参数说明：
path文件名
buf传出参数，定义结构体struct stat sb; &sb
- 返回值
失败：返回-1，设置errno
成功：返回0
注意： stat碰到链接，会追溯到源文件，穿透！！！lstat并不会穿透。
stat结构体：
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 file system I/O */ blkcnt_t st_blocks; /* number of 512B blocks allocated */ time_t st_atime; /* time of last access */ time_t st_mtime; /* time of last modification */ time_t st_ctime; /* time of last status change */ };
linux命令stat执行结果：
[root@centos linuxC]# stat stat.c 文件："stat.c" 大小：1857 块：8 IO 块：4096 普通文件 设备：fd00h/64768d Inode：17763202 硬链接：1 权限：(0644/-rw-r--r--) Uid：( 0/ root) Gid：( 0/ root) 环境：unconfined_u:object_r:usr_t:s0 最近访问：2019-04-27 19:17:15.149083960 +0800 最近更改：2019-04-27 19:17:15.149083960 +0800 最近改动：2019-04-27 19:17:15.202084912 +0800
注意三个时间的区别：
time_t st_atime; /* time of last access */ 文件被读，比如cat，open读等 time_t st_mtime; /* time of last modification */ 文件内容发生改变 time_t st_ctime; /* time of last status change */ 文件属性发生变化，比如大小，权限，硬连接数等
上图的解释：
0-2 其他用户权限 3-5 组用户权限 6-8 用户权限 9-11 特殊权限位 12-15 文件类型
示例：
1 #include <sys/types.h> 2 #include <sys/stat.h> 3 #include <time.h> 4 #include <stdio.h> 5 #include <stdlib.h> 6 7 int 8 main(int argc, char *argv[]) 9 { 10 struct stat sb; 11 12 if (argc != 2) { 13 fprintf(stderr, "Usage: %s <pathname>\n", argv[0]); 14 exit(EXIT_FAILURE); 15 } 16 17 if (stat(argv[1], &sb) == -1) { 18 perror("stat"); 19 exit(EXIT_FAILURE); 20 } 21 22 printf("File type: "); 23 24 switch (sb.st_mode & S_IFMT) { 25 case S_IFBLK: printf("block device\n"); break; 26 case S_IFCHR: printf("character device\n"); break; 27 case S_IFDIR: printf("directory\n"); break; 28 case S_IFIFO: printf("FIFO/pipe\n"); break; 29 case S_IFLNK: printf("symlink\n"); break; 30 case S_IFREG: printf("regular file\n"); break; 31 case S_IFSOCK: printf("socket\n"); break; 32 default: printf("unknown?\n"); break; 33 } 34 printf("I-node number: %ld\n", (long) sb.st_ino); 35 36 printf("Mode: %lo (octal)\n", 37 (unsigned long) sb.st_mode); 38 39 printf("Link count: %ld\n", (long) sb.st_nlink); 40 printf("Ownership: UID=%ld GID=%ld\n", 41 (long) sb.st_uid, (long) sb.st_gid); 42 43 printf("Preferred I/O block size: %ld bytes\n", 44 (long) sb.st_blksize); 45 printf("File size: %lld bytes\n", 46 (long long) sb.st_size); 47 printf("Blocks allocated: %lld\n", 48 (long long) sb.st_blocks); 49 50 printf("Last status change: %s", ctime(&sb.st_ctime)); 51 printf("Last file access: %s", ctime(&sb.st_atime)); 52 printf("Last file modification: %s", ctime(&sb.st_mtime)); 53 54 exit(EXIT_SUCCESS); 55 }