/*
From readlink(2)

gcc -g -Wall -o test_readlink test_readlink.c

GNU/Linux:
./test_readlink /proc/self/exe
bufsize = 4096
'/proc/self/exe' points to '/home/srs/Hurd/DEBs/test_cases/test_readlink'

GNU/Hurd:
./test_readlink /proc/self/exe
bufsize = 16
'/proc/self/exe' points to './test_readlink'
*/

#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

#ifndef PATH_MAX
#define PATH_MAX 4096
#endif

int
main(int argc, char *argv[])
{
  struct stat sb;
  char *linkname;
  ssize_t r, bufsiz;

  if (argc != 2) {
    fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  if (lstat(argv[1], &sb) == -1) {
    perror("lstat");
    exit(EXIT_FAILURE);
  }

  bufsiz = sb.st_size + 1;

  /* Some magic symlinks under (for example) /proc and /sys
     report 'st_size' as zero. In that case, take PATH_MAX as
     a "good enough" estimate */

  if (sb.st_size == 0)
    bufsiz = PATH_MAX;

  printf("bufsize = %zd\n", bufsiz);

  linkname = malloc(bufsiz);
  if (linkname == NULL) {
    perror("malloc");
    exit(EXIT_FAILURE);
  }

  r = readlink(argv[1], linkname, bufsiz);
  if (r == -1) {
    perror("readlink");
    exit(EXIT_FAILURE);
  }

  linkname[r] = '\0';

  printf("'%s' points to '%s'\n", argv[1], linkname);

  if (r == bufsiz)
    printf("(Returned buffer may have been truncated)\n");

  free(linkname);
  exit(EXIT_SUCCESS);
}