echo ! printing !
! false
echo $?
! true
echo $?
if ! false; then false; echo $?; fi
echo $?
if ! false; then ! false; echo $?; fi
echo $?
for a in ! a b c; do echo $a; done
for a in ! a b c; do ! echo -n "$a "; echo $?; done
for a in ! a b c; do ! /bin/echo -n "$a "; echo $?; done
for a in ! a b c; do ! echo -n "$a " | false; echo $?; done
for a in ! a b c; do ! echo -n "$a " | true; echo $?; done
for a in ! a b c; do ! { echo -n "$a " | false; }; echo $?; done
for a in ! a b c; do ! { echo -n "$a " | true; }; echo $?; done