bash – 将命令输出的错误消息存储到shell变量中

发布时间：2020-12-15 21:10:01 所属栏目：安全来源：网络整理

导读：参见英文答案 How to get error output and store it in a variable or file????????????????????????????????????3个我试图将复制命令的错误消息存储到变量中.但它没有发生 Unix命令 log=`cp log.txt`cp: missing destination file operand after `log.txt

参见英文答案 > How to get error output and store it in a variable or file????????????????????????????????????3个
我试图将复制命令的错误消息存储到变量中.但它没有发生

Unix命令

log=`cp log.txt`
cp: missing destination file operand after `log.txt'
Try `cp --help' for more information.

echo $log

<nothing displayed>

我想将上面的错误消息存储到变量中,以便我可以随时回应它

解决方法

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.

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.

（编辑：李大同）

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