shell 脚本的作用： >&2 echo “hi”

A shell scripting question! 😊

The command >&2 echo "hi" is using a feature called “file descriptor redirection” in the shell.

Here’s a breakdown of what’s happening:

• >&2: This is the redirection operator. The & symbol is used to specify a file descriptor, and the 2 specifies the file descriptor number.
• echo "hi": This is the command that prints the string “hi” to the standard output.

When you combine these two parts, the command >&2 echo "hi" redirects the output of the echo command to file descriptor 2, which is the standard error (stderr).

In other words, the command is saying: “Take the output of the echo command and send it to the standard error stream instead of the standard output stream.”

The effect of this command is that the string “hi” will be printed to the standard error stream, which is usually displayed on the console.

Here’s an example of how you might use this command in a script:

#!/bin/bash

# Print an error message to stderr
>&2 echo "Error: something went wrong!"

# Print a success message to stdout
echo "Success: everything is okay!"

When you run this script, the error message will be printed to stderr, and the success message will be printed to stdout.

Note that file descriptor redirection is a powerful feature in shell scripting, and it can be used to redirect input/output streams in various ways.