libc-top-half/musl/src/misc/realpath.c

   1 #include <stdlib.h>
   2 #include <limits.h>
   3 #include <sys/stat.h>
   4 #include <fcntl.h>
   5 #include <errno.h>
   6 #include <unistd.h>
   7 #include <string.h>
   8 #include "syscall.h"
   9
  10 char *realpath(const char *restrict filename, char *restrict resolved)
  11 {
  12         int fd;
  13         ssize_t r;
  14         struct stat st1, st2;
  15         char buf[15+3*sizeof(int)];
  16         char tmp[PATH_MAX];
  17
  18         if (!filename) {
  19                 errno = EINVAL;
  20                 return 0;
  21         }
  22
  23         fd = sys_open(filename, O_PATH|O_NONBLOCK|O_CLOEXEC);
  24         if (fd < 0) return 0;
  25         __procfdname(buf, fd);
  26
  27         r = readlink(buf, tmp, sizeof tmp - 1);
  28         if (r < 0) goto err;
  29         tmp[r] = 0;
  30
  31         fstat(fd, &st1);
  32         r = stat(tmp, &st2);
  33         if (r<0 || st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino) {
  34                 if (!r) errno = ELOOP;
  35                 goto err;
  36         }
  37
  38         __syscall(SYS_close, fd);
  39         return resolved ? strcpy(resolved, tmp) : strdup(tmp);
  40 err:
  41         __syscall(SYS_close, fd);
  42         return 0;
  43 }