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看起来像尾随'\n'字符被修剪为"$()",，而我从bash manual找不到关于此的任何规范。这真的让人困惑，任何人都可以帮我解释一下吗？
[[email protected]_6_207_centos ~]$ a="$(echo $'abc\n\n' | cat)"
[[email protected]_6_207_centos ~]$ echo "$a"
abc
[[email protected]_6_207_centos ~]$ a="$(echo $'abc\n\nb' | cat)"
[[email protected]_6_207_centos ~]$ echo "$a"
abc
b
[[email protected]_6_207_centos ~]$ a=$'abc\n'
[[email protected]_6_207_centos ~]$ echo "$a"
abc
[[email protected]_6_207_centos ~]$ a="$(echo $'abc ' | cat)"
[[email protected]_6_207_centos ~]$ echo "$a" | url_encode
abc%20%20%0A[[email protected]_6_207_centos ~]$