UNIX shell while [ "$yn" = "yes" -a "$yn" = "YES" ] until [ "$yn" == "yes" -a "$yn" == "YES" ]上面两句里面的 -a 和-o 和&& | 一样吗

UNIX shell while [ "$yn" = "yes" -a "$yn" = "YES" ] until [ "$yn" == "yes" -a "$yn" == "YES" ]上面两句里面的 -a 和-o 和&& | 一样吗
UNIX shell while [ "$yn" = "yes" -a "$yn" = "YES" ] until [ "$yn" == "yes" -a "$yn" == "YES" ]
上面两句里面的 -a 和-o
和&& | 一样吗

UNIX shell while [ "$yn" = "yes" -a "$yn" = "YES" ] until [ "$yn" == "yes" -a "$yn" == "YES" ]上面两句里面的 -a 和-o 和&& | 一样吗
-a 表示 与 and
-o 表示 或 or
-a 和 && 一样,-o 和||一样,但&&和||需要在方括号外使用：
while [ "$yn" != "yes" ] && [ "$yn" != "YES" ]
until [ "$yn" == "yes" ] || [ "$yn" == "YES" ]