Getuser returns a pointer to static data which contains the
name of the user who
owns the current process.
and then reads
/etc/passwd to find the corresponding name.
Sysname returns a pointer to static data which contains the name
of the machine on which the current process is running.
Sysname looks first for an environment variable
$sysname. If there is no such variable,
and truncates the returned name at the first dot.
sysname returns the default name
sysname caches the string, deriving the host name only once.