What's the difference between

bash中看到这样的命令，

curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
sudo apt-get install -y nodejs

黄色部分，| 这个是管道操作符，表示前面命令的输出作为后面的命令的输入。 "bash -" bash 跟一个短杠的作用是什么呢？ 
For a command, if using - as an argument in place of a file name will mean STDIN or STDOUT.

参考：https://askubuntu.com/questions/813303/whats-the-difference-between-one-hyphen-and-two-hyphens-in-a-command

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Generally:

• - means to read the argument/content from STDIN (file descriptor 0)

• -- means end of command options, everything follows that are arguments

Why needed:

About -:

$ echo foobar | cat -
foobar

Although cat can read content from STDIN without needing the -, many commands need that and their man pages mention that explicitly.

Now about --, I have created a file -spam, let's cat the file:

$ echo foobar >-spam  
 
$ cat -spam         
cat: invalid option -- 'p'
Try 'cat --help' for more information.
 
$ cat -- -spam      
foobar

Without --, cat takes s, p, a, m all as it's options as they follow -, -- explicitly indicates the end of option(s), after that -spam is taken as a file name.