src/readlink.c

   1 /*
   2
   3 readlink.c - readlink(2) access from command line
   4 Copyright (C) 2017,2021 Kyle J. McKay.
   5 All rights reserved.
   6
   7 Permission is hereby granted, free of charge, to any person obtaining a copy
   8 of this software and associated documentation files (the "Software"), to deal
   9 in the Software without restriction, including without limitation the rights
  10 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11 copies of the Software, and to permit persons to whom the Software is
  12 furnished to do so, subject to the following conditions:
  13
  14 The above copyright notice and this permission notice shall be included in all
  15 copies or substantial portions of the Software.
  16
  17 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23 SOFTWARE.
  24
  25 */
  26
  27 #include <stdio.h>
  28 #include <limits.h>
  29 #include <unistd.h>
  30
  31 #define MIN_PATH_MAX ((PATH_MAX) >= 4096 ? (PATH_MAX) : 4096)
  32
  33 static char buf[MIN_PATH_MAX];
  34
  35 /* readlink [-n] filename */
  36 int main(int argc, char **argv)
  37 {
  38         ssize_t len;
  39         int opt_n = 0;
  40
  41         if (argc < 2 || argc > 3)
  42                 return 1;
  43         if (argc == 3) {
  44                 if (argv[1][0] != '-' || argv[1][1] != 'n' || argv[1][2] != '\0')
  45                         return 1;
  46                 opt_n = 1;
  47                 ++argv;
  48         }
  49         len = readlink(argv[1], buf, sizeof(buf) - 1);
  50         if (len <= 0 || len >= (ssize_t)sizeof(buf))
  51                 return 1;
  52         buf[len] = 0;
  53         if (opt_n)
  54                 fputs(buf, stdout);
  55         else
  56                 puts(buf);
  57         return 0;
  58 }