Bash脚本 - if和grep不起作用

Question

由于这个社区似乎非常好,所以我想我会问一个问题 -

我有这个小脚本,但它不会只是从输出中获取超时:

#!/bin/bash
echo -n "Enter ntp server address: "
read SERVER
if ntpdc -n -c monlist $SERVER | grep "timed out"
then 
  echo "Server won't let You use monlist."
  exit 0
else 
  echo "Server will let You use monlist."
fi

有任何想法吗？谢谢 :)

Answer 1

在这种情况下,"问题"是ntpdc将超时消息发送到标准错误,而不是标准输出,因此grep不会在管道输入上看到它.您可以通过将ntpdc命令的标准错误路由到标准输出来解决:

if ntpdc -n -c monlist $SERVER 2>&1 | grep "timed out"
then 
  echo "Server won't let You use monlist."
  exit 0
else 
  echo "Server will let You use monlist."
fi