bash和sh脚本中关于测试表达式的区别

有两种
[ a = b]
[[ a == b ]]

sh 只认第一种
bash 两种都认

有个脚本我一直没改好，原因是以为是bash脚本（或者说以为sh就是bash），然后就按第二种写了，但是总是没用。后来发现原来那个是sh脚本，而且man了一下发现sh和bash原来不是一回事。终于搞定了。

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