bash - 将 grep 结果保存到变量

Question

我有以下命令:

pvs /dev/sdb | grep failed

结果例如:

/dev/sdb: read failed after 0 of 4096 at 0: Input/output error
/dev/sdb: read failed after 0 of 4096 at 1073676288: Input/output error
/dev/sdb: read failed after 0 of 4096 at 1073733632: Input/output error
/dev/sdb: read failed after 0 of 4096 at 4096: Input/output error

现在我想将该结果保存到一个变量中:

STATUS=`pvs /dev/sdb | grep failed`

但是，当我阅读内容时，它是空的:

echo $STATUS

我尝试将它重定向到一个文件:

`pvs /dev/sdb | grep failed` > /tmp/hdd-status

同样的结果，文件仍然是空的。

Answer 1

您看到的消息似乎是标准错误 消息，而不是标准输出。您可以阅读有关重定向的更多信息 here .

因此，在将输出管道输出到 grep 之前，您需要将 STDERR 与 STDOUT 合并:

STATUS=`pvs /dev/sdb 2>&1 | grep failed`

此外，command substitution 的另一种形式而不是使用反引号更具可读性:

STATUS=$(pvs /dev/sdb 2>&1 | grep failed)

When the old-style backquote form of substitution is used, backslash retains its literal meaning except when followed by $, `, or \. The first backquote not preceded by a backslash terminates the command substitution. When using the $(command) form, all characters between the parentheses make up the command; none are treated specially.