linux shell 双引号、单引号、反引号

#”双引号字符串

echo let us to do *

echo "let us to do *"

grep as hu one

echo  "\n"

echo \n

grep "as hu" one

#'单引号强制引用

BOY="boy"

a='$BOY'

echo "$a"

#`反引号 作为系统命令

echo `date +%d%m`

echo `date –d ‘-6 day’ +’%Y%m%d’`