Should I use quotes to echo multiple words in bash?

Question

In shell scripts I usually use echo to print a message. When the message contains multiple words I have to options of how to do that:

# No quotes
echo Hello SO

or

# Quotes
echo 'Hello SO'

Is one way better than the other?

I know that quotes are very important when there are variables, special character, etc. So, this is another question.

Answer 1

Echo varies a lot accross implementations, but POSIX does mandate this:

STDOUT
echo 实用程序参数应由单个 <space> 字符分隔，并且 <newline> 字符应跟在最后一个参数之后。

因此，如果您不引用，shell 将完成其工作并在空格上拆分参数，然后 Echo 将输出每个参数，每个参数由一个空格分隔：

$ echo Y X Z
Y X Z
$ echo Y   X   Z
Y X Z
$ echo 'Y   X   Z'
Y   X   Z

当然，整行仍然可以包含特殊标记并且完全失败：

# Variable expansion
$ echo I have $2
I have

# Filename expansion
$ echo hi * there
hi Documents Downloads Music Pictures Videos there

# And other special tokens
$ echo hello (I am I)
bash: syntax error near unexpected token `('

如有疑问，请引用。对于您的特定示例，不，它没有区别。