#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <string.h>

int main(int argc, char ** argv) {
  int i, last_slash = -1, length;

  /* If no path given, print / per the POSIX spec */
  if(argc == 1) {
    printf("/\n");
    return 0;
  }

  /* Same if // is given */
  if(strcmp(argv[1], "//") == 0) {
    printf("/\n");
    return 0;
  }

  /* Oh, look, we use strlen here. */
  length = strlen(argv[1]);

  /* Replace terminal slash (if present) with null */
  if(argv[1][length - 1] == '/') {
    argv[1][length - 1] = '\0';
  }

  /* Find last slash */
  for(i = 0; i < length; i++) {
    if(argv[1][i] == '/') {
      last_slash = i;
    }
  }

  /* If we didn't find a slash, assume PWD per POSIX spec */
  if(last_slash == -1) {
    printf(".\n");
    return 0;
  }

  /* Replace last slash with null to truncate basename */
  argv[1][last_slash] = '\0';

  /* If the dirname is //, /, or blank, print a single slash. */
  if(strcmp(argv[1], "//") == 0 || strcmp(argv[1], "") == 0 ||
     strcmp(argv[1], "/") == 0) {
    printf("/\n");
    return 0;
  }

  /* Remove any trailing slashes from the dirname */
  for(i = last_slash - 1; argv[1][i] == '/'; i--) {
    argv[1][i] = '\0';
  }

  printf("%s\n", argv[1]);

  return 0;
}