shell 字符串比較是否相等 報錯[: =: unary operator expected

shell 字符串比較是否相等  報錯[: =: unary operator expected

egg:

a = '123'

b='1234'

if [  $a  ==  $b ]；then

echo "相等"

fi

此時報錯[: =: unary operator expected

正確寫法  多加個[ ]：

if [[  $a  ==  $b ]]；then

echo "相等"

fi