Get Computer Name and logged user name

Question

I am developing an application. One of the methods needs to capture the computer name and user logged on the machine, then display both to the user. I need it to run on both Win

Answer 1

On POSIX systems you can use the gethostname and getlogin functions, both declared in unistd.h.

/*
   This is a C program (I've seen the C++ tag too late).  Converting
   it to a pretty C++ program is left as an exercise to the reader.
*/

#include 
#include 
#include 
#include 

int
main()
{
  char hostname[HOST_NAME_MAX];
  char username[LOGIN_NAME_MAX];
  int result;
  result = gethostname(hostname, HOST_NAME_MAX);
  if (result)
    {
      perror("gethostname");
      return EXIT_FAILURE;
    }
  result = getlogin_r(username, LOGIN_NAME_MAX);
  if (result)
    {
      perror("getlogin_r");
      return EXIT_FAILURE;
    }
  result = printf("Hello %s, you are logged in to %s.\n",
                  username, hostname);
  if (result < 0)
    {
      perror("printf");
      return EXIT_FAILURE;
    }
  return EXIT_SUCCESS;
}

Possible output:

Hello 5gon12eder, you are logged in to example.com.

This seems safer than relying on environment variables which are not always present.

I'm withdrawing that last statement because

• the man page of getlogin actually discourages its usage in favour of getenv("LOGIN") and
• the getlogin_r call in the above program fails with ENOTTY when I run the program from within Emacs instead of an interactive terminal while getenv("USER") would have worked in both situations.