bash - 将命令输出的错误消息存储到 shell 变量中

Question

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Answer 1

只需将 stdout(正常输出)重定向到 /dev/null 并保留 stderror:

a=$(cp log.txt 2>&1 >/dev/null)

看一个例子:

$ a=$(cp log.txt 2>&1 >/dev/null)
$ echo "$a"
cp: missing destination file operand after ‘log.txt’
Try 'cp --help' for more information.

>/dev/null 避免正常输出的重要性，在这种情况下我们不希望这样:

$ ls a b
ls: cannot access a: No such file or directory
b
$ a=$(ls a b 2>&1)
$ echo "$a"
ls: cannot access a: No such file or directory
b
$ a=$(ls a b 2>&1 >/dev/null)
$ echo "$a"
ls: cannot access a: No such file or directory

注意调用时需要引用$a，这样格式就保持不变了。此外，最好使用 $() 而不是 ，因为它更容易嵌套，而且 已被弃用。

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What does 2>&1 mean?

1 is stdout. 2 is stderr.

Here is one way to remember this construct (altough it is not entirely accurate): at first, 2>1 may look like a good way to redirect stderr to stdout. However, it will actually be interpreted as "redirect stderr to a file named 1". & indicates that what follows is a file descriptor and not a filename. So the construct becomes: 2>&1.