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对于保持正常输出的重要性,在这种情况下我们不需要：

$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

注意在调用它时需要引用$a,以便保留格式.此外,最好使用$()而不是,因为它更容易嵌套并且也被弃用.

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.