libbb/xreadlink.c

   1 /*
   2  *  xreadlink.c - safe implementation of readlink.
   3  *  Returns a NULL on failure...
   4  */
   5
   6 #include <stdio.h>
   7
   8 /*
   9  * NOTE: This function returns a malloced char* that you will have to free
  10  * yourself. You have been warned.
  11  */
  12
  13 #include <unistd.h>
  14 #include "libbb.h"
  15
  16 extern char *xreadlink(const char *path)
  17 {
  18         static const int GROWBY = 80;   /* how large we will grow strings by */
  19
  20         char *buf = NULL;
  21         int bufsize = 0, readsize = 0;
  22
  23         do {
  24                 buf = xrealloc(buf, bufsize += GROWBY);
  25                 readsize = readlink(path, buf, bufsize);        /* 1st try */
  26                 if (readsize == -1) {
  27                         perror_msg("%s", path);
  28                         free(buf);
  29                         return NULL;
  30                 }
  31         }
  32         while (bufsize < readsize + 1);
  33
  34         buf[readsize] = '\0';
  35
  36         return buf;
  37 }