$ sudo mousepad

su --command="mousepad"

su -c "mousepad"

When sudo runs a command, it calls fork(2), sets up the execution
environment as described above, and calls the execve system call in
the child process. The main sudo process waits until the command has
completed, then passes the command's exit status to the security
policy's close function and exits. If an I/O logging plugin is
configured or if the security policy explicitly requests it, a new
pseudo-terminal (“pty”) is created and a second sudo process is used
to relay job control signals between the user's existing pty and the
new pty the command is being run in. This extra process makes it
possible to, for example, suspend and resume the command. Without it,
the command would be in what POSIX terms an “orphaned process group”
and it would not receive any job control signals. As a special case,
if the policy plugin does not define a close function and no pty is
required, sudo will execute the command directly instead of calling
fork(2) first. The sudoers policy plugin will only define a close
function when I/O logging is enabled, a pty is required, or the
pam_session or pam_setcred options are enabled. Note that pam_session
and pam_setcred are enabled by default on systems using PAM.