I am trying to echo the content of quotes.txt and also use the say command to speak it：

cat quotes.txt | xargs echo | say

The say command did work, but the content of quotes.txt didn't show in my terminal, which means echo didn't take effect but it indeed passed the content to the say command.

does anyone know why echo didn't work as the mid-seat in a pipeline?

Thank you!

I think I know the reason. Sorry guys

The pipe redirects the echo output to the following command.
If you want both the terminal and "say" then you must duplicate it.
One method is "tee" that writes to stdout AND to a file.
And if the file is a special file that forwards to the terminal then it prints immediately.
xargs does nothing but changing embedded newlines to spaces. Perhaps you can skip it?
Another special file is a "process substitution":
Of course you can save an output to a file (redirection) or a variable (command substitution) and use the file or variable twice.
In this case you have a file already.

I guesscan work too without cat
and also probably
is enough

Ah yes, "cat" is just a place holder; not needed if "say" can be used there:
Also saving the descriptor magic.