pwd.c

//  Copyright (C) 2021 Benjamin Stürz
//  
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//  
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//  
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.

#include <limits.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

int main(int argc, char* argv[]) {
   int resolve_links = 0;
   int option;
   while ((option = getopt(argc, argv, ":LP")) != -1) {
      switch (option) {
      case 'P': resolve_links = 1; break;
      case 'L': resolve_links = 0; break;
      default: goto print_usage;
      }
   }
   int free_pwd = 0;
   char* pwd = getenv("PWD");
   if (!pwd) {
      pwd = (char*)malloc(PATH_MAX + 1);
      if (!pwd) {
         perror("pwd: Failed to allocate buffer");
         abort();
      }
      if (!getcwd(pwd, PATH_MAX)) {
         perror("pwd: Failed to get current working directory");
         free(pwd);
         return 1;
      }
   }
   int ec = 0;
   if (resolve_links) {
      char buf[PATH_MAX + 1];
      if (!realpath(pwd, buf)) {
         perror("pwd: Failed to resolve path");
         ec = 1;
      }
      else puts(buf);
   }
   else puts(pwd);
   if (free_pwd) free(pwd);
   return ec;
print_usage:
   fputs("Usage: pwd [-L|-P]\n", stderr);
   return 1;
}