管道无法与echo命令一起使用 [英] Piping not working with echo command

问题描述

当我运行以下Bash脚本时，我希望它可以打印Hello.而是打印空白行并退出.

When I run the following Bash script, I would expect it to print Hello. Instead, it prints a blank line and exits.

echo 'Hello' | echo

为什么piping从echo输出到echo无效?

推荐答案

echo打印所有参数.它不会从stdin读取.因此，第二个echo打印所有参数(无)并退出，而忽略stdin上的Hello.

echo prints all of its arguments. It does not read from stdin. So the second echo prints all of its arguments (none) and exits, ignoring the Hello on stdin.

对于读取其stdin并将其打印到stdout的程序，请使用cat:

For a program that reads its stdin and prints that to stdout, use cat:

$ echo Hello | cat
Hello

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