ls -li 文件名

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

int stat(const char *pathname, struct stat *statbuf);
int fstat(int fd, struct stat *statbuf);
int lstat(const char *pathname, struct stat *statbuf);

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 */
    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;  /* Block size for filesystem I/O */
    blkcnt_t st_blocks;  /* Number of 512B blocks allocated */

    /* Since Linux 2.6, the kernel supports nanosecond
     precision for the following timestamp fields.
     For the details before Linux 2.6, see NOTES. */

    struct timespec st_atim; /* Time of last access */
    struct timespec st_mtim; /* Time of last modification */
    struct timespec st_ctim; /* Time of last status change */

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

判斷文件類(lèi)型的函數(shù)，返回true，false  
 S_ISREG(stat.st_mode) is it a regular file?
 S_ISDIR(stat.st_mode) directory?
 S_ISCHR(stat.st_mode) character device?
 S_ISBLK(stat.st_mode) block device?
 S_ISFIFO(m) FIFO (named pipe)?
 S_ISLNK(stat.st_mode) symbolic link? (Not in POSIX.1-1996.)
 S_ISSOCK(stat.st_mode) socket? (Not in POSIX.1-1996.)

 S_ISUID  04000 set-user-ID bit
  S_ISGID  02000 set-group-ID bit (see below)
  S_ISVTX  01000 sticky bit (see below)

  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

struct timespec {
	__kernel_time_t	tv_sec;	 /* seconds */當(dāng)前時(shí)間到1970.1.1 00:00:00的秒數(shù)
	long		tv_nsec;	/* nanoseconds *//納秒數(shù)（不知道從哪到哪的）
};
1s 秒  = 1000ms 毫秒
1ms 毫秒 = 1000us 微秒
1us 微秒 = 1000ns 納秒

ys@ys-VirtualBox:~/lianxi1$ stat hello
 File: hello
 Size: 11  	Blocks: 8   IO Block: 4096 regular file
Device: 801h/2049d	Inode: 3801352  Links: 2
Access: (0764/-rwxrw-r--) Uid: ( 1000/  ys) Gid: ( 1000/  ys)
Access: 2019-04-24 17:02:39.199461489 +0800
Modify: 2019-04-24 16:54:16.407461489 +0800
Change: 2019-04-24 17:03:44.927461489 +0800

#include <sys/types.h>
#include <pwd.h>
struct passwd *getpwnam(const char *name);
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 */
};

#include <sys/types.h>
#include <grp.h>
struct group *getgrnam(const char *name);
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 */
};

#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 */
};

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

int main(int argc, char* argv[]){

 struct stat sbuf;
 //stat(argv[1], &sbuf);
 lstat(argv[1], &sbuf);

 char str[11] = {0};
 memset(str, '-', (sizeof str - 1));
 
 //文件類(lèi)型
 if(S_ISREG(sbuf.st_mode)) str[0] = '-';
 if(S_ISDIR(sbuf.st_mode)) str[0] = 'd';
 if(S_ISCHR(sbuf.st_mode)) str[0] = 'c';
 if(S_ISBLK(sbuf.st_mode)) str[0] = 'b';
 if(S_ISFIFO(sbuf.st_mode)) str[0] = 'p';
 if(S_ISLNK(sbuf.st_mode)) str[0] = 'l';
 if(S_ISSOCK(sbuf.st_mode)) str[0] = 's';

 //本用戶(hù)的文件權(quán)限
 if(sbuf.st_mode & S_IRUSR) str[1] = 'r';
 if(sbuf.st_mode & S_IWUSR) str[2] = 'w';
 if(sbuf.st_mode & S_IXUSR) str[3] = 'x';
 
 //本用戶(hù)的組的文件權(quán)限
 if(sbuf.st_mode & S_IRGRP) str[4] = 'r';
 if(sbuf.st_mode & S_IWGRP) str[5] = 'w';
 if(sbuf.st_mode & S_IXGRP) str[6] = 'x';
 
 //其他用戶(hù)的文件權(quán)限
 if(sbuf.st_mode & S_IROTH) str[7] = 'r';
 if(sbuf.st_mode & S_IWOTH) str[8] = 'w';
 if(sbuf.st_mode & S_IXOTH) str[9] = 'x';

 char ymd[20] = {0};
 //取得日期和時(shí)間
 struct tm* tm = localtime(&sbuf.st_atim.tv_sec);
 sprintf(ymd, "%2d月 %2d %02d:%02d", tm->tm_mon + 1, tm->tm_mday,
	 tm->tm_hour + 1,tm->tm_sec);
 
 //-rw-r--r-- 1 ys ys 134 4月 25 09:21 st2.c
 printf("%s %ld %s %s %ld %s %s\n", str, sbuf.st_nlink,
	 getpwuid(sbuf.st_uid)->pw_name, getgrgid(sbuf.st_gid)->gr_name,
	 sbuf.st_size, ymd, argv[1]);
 return 0;
}

#include <unistd.h>
int access(const char *pathname, int mode);

#include <stdio.h>
#include <unistd.h>//access

int main(int argc, char* argv[]){
 if(access(argv[1], R_OK) == 0)
 printf("read ok\n");
 if(access(argv[1], W_OK) == 0)
 printf("write ok\n");
 if(access(argv[1], X_OK) == 0)
 printf("exe ok\n");
 if(access(argv[1], F_OK) == 0)
 printf("exists\n");
}

ys@ys-VirtualBox:~/lianxi$ ls -l /usr/include/time.h
-rw-r--r-- 1 root root 10360 4月 17 2018 /usr/include/time.h

ys@ys-VirtualBox:~/lianxi$ ./ac /usr/include/time.h
read ok
exists

ys@ys-VirtualBox:~/lianxi$ sudo ./ac /usr/include/time.h
[sudo] password for ys: 
read ok
write ok
exists

#include <unistd.h>
#include <sys/types.h>
int truncate(const char *path, off_t length);

#include <unistd.h>
int link(const char *oldpath, const char *newpath);

#include <unistd.h>
int symlink(const char *target, const char *linkpath);

#include <unistd.h>
ssize_t readlink(const char *pathname, char *buf, size_t bufsiz);

#include <unistd.h>
int unlink(const char *pathname);

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

int main(){
 int fd = open("hello", O_WRONLY | O_CREAT, 0666);
 unlink("hello");
 int ret = write(fd, "aaa", 4);
 if(ret > 0){
 printf("write OK\n");
 }
 
}

#include <unistd.h>
int chown(const char *pathname, uid_t owner, gid_t group);

#include <stdio.h>
int rename(const char *oldpath, const char *newpath);

#include <unistd.h>
char *getcwd(char *buf, size_t size);

#include <unistd.h>
int chdir(const char *path);

#include <sys/stat.h>
#include <sys/types.h>
int mkdir(const char *pathname, mode_t mode);

#include <unistd.h>
int rmdir(const char *pathname);

#include <sys/types.h>
#include <dirent.h>
DIR *opendir(const char *name);

#include <sys/types.h>
#include <dirent.h>
DIR *opendir(const char *name);

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

#include <string.h>
char *strerror(int errnum);

#include <string.h>
#include <stdio.h>
#include <asm-generic/errno.h>//EDEADLK
int main(){
 char* buf = strerror(EDEADLK);
 printf("%s\n", buf);//Resource deadlock avoided
}

#include <unistd.h>
int dup(int oldfd);
int dup2(int oldfd, int newfd);

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

int main(){

 int oldfd = dup(STDOUT_FILENO);
 int fd = open("www", O_WRONLY | O_CREAT, 0666);
 dup2(fd, STDOUT_FILENO);
 printf("aaaa\n");
 fflush(stdout);
 int ret = dup2(oldfd, STDOUT_FILENO);
 //int ret = dup2(oldfd, 6);
 //perror("dup2:");
 printf("reg:%d\n", ret);
 printf("aaaa\n");
 close(fd);
}