#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <unistd.h>

char *env(char *);

int main(int argc, char *argv[]) {
  if (argc < 2) for (; *environ; environ++)
    printf("%s\n", *environ);
  else printf("%s = \"%s\"\n", argv[1], env(argv[1]));

  return 0;
}

char *env(char *name) {
  for (; *environ; environ++)
    if (!strncmp(*environ, name, strlen(name))
	&& *(*environ+strlen(name)) == '=')
      return (*environ)+strlen(name)+1;

  return 0;
}