If you're appending only a single line instead of multiple lines or an entire file, you can use echo instead of cat.

如果您仅追加单行而不是多行或整个文件，您可以使用echo而不是cat。

youdao

Did you also notice the use of double-quoted strings instead of single-quoted strings on the echo line?

另外，你注意到在echo一行它使用了双引号而不是单引号吗？

youdao

You also find that each line, each vertex has an echo, it expands to something else; a change of color or texture, or a simple line drawn over the floor. Another gesture that connects with the whole.

你还会发现每个线条和每个顶点都有回应，它扩展到别的东西：可能是颜色或纹理的改变，或者是地板上画的简单线条，它们都以另一种姿态与整体相连。

youdao

This is the story of Echo Taps: The Long Brass Line.

FORBES: 42 Miles Of Echo Taps: A Memorial Day Tribute