To ignore a signal, use two single quotes in place of the command_list
要忽略某个信号，使用两个单引号代替 command_list
Atoms must start with a lower case character, or you can delimit with single quotes.
原子值必须以小写字母开头，否则需要加上单引号。
Single quotes are better, because then you can use double quotes inside the one-liner.
单引号更好，因为使用单引号后您可以在一行程序内使用双引号。
Single quotes are better, because then you can use double quotes inside the one-liner.
单引号更好，因为使用单引号后您可以在一行程序内使用双引号。
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