Unix/Linux文件类型及访问权限

  1 /*
  2  * foo.c - get Unix/Linux file type and its access,
  3  *         mostly simliar to what GNU stat does
  4  */
  5 
  6 #include <stdio.h>
  7 #include <string.h>
  8 #include <sys/types.h>
  9 #include <sys/stat.h>
 10 #include <unistd.h>
 11 #include <errno.h>
 12 
 13 int
 14 main(int argc, char *argv[])
 15 {
 16     char        *filepath = NULL;
 17     char        *filetype = NULL;
 18     char        s[] = "----------";
 19     int        rc;
 20     struct stat    sb;
 21 
 22     if (argc != 2) {
 23         (void) fprintf(stderr, "Usage %s <file>\n", argv[0]);
 24         return (-1);
 25     }
 26 
 27     filepath = argv[1];
 28 
 29     (void) memset(&sb, 0, sizeof (struct stat));
 30 
 31     errno = 0;
 32     /* NOTE: don‘t use stat() as we will get symbolic link file type */
 33     if ((rc = lstat(filepath, &sb)) != 0) {
 34         (void) fprintf(stderr, "%s: cannot stat `%s‘: %s\n",
 35             argv[0], filepath, strerror(errno));
 36         return (-1);
 37     }
 38 
 39     /* get file type */
 40     if (S_ISREG(sb.st_mode)) {
 41         s[0] = ‘-‘;
 42         filetype = "regular file";
 43     }
 44     if (S_ISDIR(sb.st_mode)) {
 45         s[0] = ‘d‘;
 46         filetype = "directory";
 47     }
 48     if (S_ISCHR(sb.st_mode)) {
 49         s[0] = ‘c‘;
 50         filetype = "character special file";
 51     }
 52     if (S_ISBLK(sb.st_mode)) {
 53         s[0] = ‘b‘;
 54         filetype = "block special file";
 55     }
 56     if (S_ISFIFO(sb.st_mode)) {
 57         s[0] = ‘p‘;
 58         filetype = "fifo";
 59     }
 60     if (S_ISLNK(sb.st_mode)) {
 61         s[0] = ‘l‘;
 62         filetype = "symbolic link";
 63     }
 64     if (S_ISSOCK(sb.st_mode)) {
 65         s[0] = ‘s‘;
 66         filetype = "socket";
 67     }
 68 #ifdef __sunos
 69     if (S_ISDOOR(sb.st_mode)) {
 70         s[0] = ‘D‘;
 71         filetype = "door";
 72     }
 73 #endif
 74 
 75     /* parse set UID, set-group-ID, sticky bit */
 76     if (sb.st_mode & S_ISUID)
 77         s[3] = ‘S‘;
 78     if (sb.st_mode & S_ISGID)
 79         s[6] = ‘S‘;
 80     if (sb.st_mode & S_ISVTX)
 81         s[9] = ‘T‘;
 82 
 83     /* parse owner rwx bit */
 84     if (sb.st_mode & S_IRUSR)
 85         s[1] =‘r‘;
 86     if (sb.st_mode & S_IWUSR)
 87         s[2] =‘w‘;
 88     if (sb.st_mode & S_IXUSR)
 89         s[3] = (s[3] == ‘S‘) ? ‘s‘ : ‘x‘;
 90 
 91     /* parse group rwx bit */
 92     if (sb.st_mode & S_IRGRP)
 93         s[4] = ‘r‘;
 94     if (sb.st_mode & S_IWGRP)
 95         s[5] = ‘w‘;
 96     if (sb.st_mode & S_IXGRP)
 97         s[6] = (s[6] == ‘S‘) ? ‘s‘ : ‘x‘;
 98 
 99     /* parse others rwx bit */
100     if (sb.st_mode & S_IROTH)
101         s[7] = ‘r‘;
102     if (sb.st_mode & S_IWOTH)
103         s[8] = ‘w‘;
104     if (sb.st_mode & S_IXOTH)
105         s[9] = (s[9] == ‘T‘) ? ‘t‘ : ‘x‘;
106 
107     (void) printf("  File: %s\n", filepath);
108     (void) printf("Access: (%04o/%s)\n", (int)(sb.st_mode & ~S_IFMT), s);
109     (void) printf("  Type: %s\n", filetype);
110 
111     return (0);
112 }

$ gcc -g -Wall -m32 -o foo foo.c

$ ./foo /usr/bin/passwd
  File: /usr/bin/passwd
Access: (4755/-rwsr-xr-x)
  Type: regular file

$ ./foo /var/tmp
  File: /var/tmp
Access: (1777/drwxrwxrwt)
  Type: directory

$ ./foo /bin/sh
  File: /bin/sh
Access: (0777/lrwxrwxrwx)
  Type: symbolic link

$ mkfifo /tmp/fifo
$ ./foo /tmp/fifo
  File: /tmp/fifo
Access: (0664/prw-rw-r--)
  Type: fifo

$ ./foo /dev/null
  File: /dev/null
Access: (0666/crw-rw-rw-)
  Type: character special file

$ ./foo /dev/sda
  File: /dev/sda
Access: (0660/brw-rw----)
  Type: block special file

$ ./foo /var/tmp/.sshmux 
  File: /var/tmp/.sshmux
Access: (0600/srw-------)
  Type: socket