Lock this display. Call a screenlock program (
/usr/bin/lock or a builtin if no other is available).
not accept any command keys until this program terminates. Meanwhile,
processes in the windows may continue, as the windows are in the
“detached” state. The screenlock program may be changed through the
environment variable $LOCKPRG (which must be set in
the shell from which screen is started) and is executed with the user's
uid and gid.
Warning: When you leave other shells unlocked and you have no password
screen, the lock is effectively void: one could easily
re-attach from an unlocked shell. This feature should rather be called