#include < pwd.h>
#include < sys/types.h>
 
char *get_home_dir (void)
{
    char *homedir;
    if ((homedir = getenv("HOME")) == NULL)
    {
        homedir = getpwuid(getuid())->pw_dir;
    }
    return homedir;
}

[Ссылки]

1. Get home directory in Linux site:stackoverflow.com.
2. man getpwnam getpwuid site:opennet.ru.