pwd.c

   1 /* `pwd.c` - return working directory name
   2    Copyright (c) 2022, Alan Potteiger
   3    See `LICENSE` for copyright and license details */
   4
   5 #define _POSIX_C_SOURCE 200809L
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <unistd.h>
  10
  11 static const char *usage = {
  12         "usage: pwd [-L|-P]\n"
  13 };
  14
  15 int
  16 main(int argc, char *argv[])
  17 {
  18         char c;
  19         char *wd, *p;
  20         int flag;
  21
  22         /* 0 == -L
  23            1 == -P */
  24         flag = 0;
  25
  26         while ((c = getopt(argc, argv, "LP")) != -1) {
  27                 switch (c) {
  28                 case 'L':
  29                         flag = 0;
  30                         break;
  31                 case 'P':
  32                         flag = 1;
  33                         break;
  34                 case '?':
  35                 default:
  36                         fputs(usage, stderr);
  37                         return 1;
  38                 }
  39         }
  40
  41         if (flag)
  42                 goto pflag;
  43
  44         /* -L */
  45         wd = getenv("PWD");
  46         if (wd == NULL)
  47                 goto pflag;
  48
  49         /* test pathname from $PWD for ./ or ../
  50            if they exist, jump to the -P option */
  51         p = wd;
  52         for (; *p != '\0'; p++) {
  53                 if (*p == '/')
  54                         continue;
  55                 if (*p == '.') {
  56                         if (*(p+1) == '.' && *(p+1) == '/')
  57                                 goto pflag;
  58                         if (*(p+1) == '/')
  59                                 goto pflag;
  60                 }
  61         }
  62
  63         printf("%s\n", wd);
  64         return 0;
  65
  66 pflag:  /* -P */
  67         wd = getcwd(NULL, 0);
  68         if (wd == NULL) {
  69                 perror("pwd");
  70                 return 1;
  71         }
  72
  73         printf("%s\n", wd);
  74
  75         free(wd);
  76         return 0;
  77 }
  78