Bash script - if and grep won't work

Question

As this community seems to be really nice so I thought I'd ask a question -

I have this little script but it won't just grep the timed out from the output:

#!/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

Any ideas? Thanks :)

What is the output of ntpdc -n -c monlist $SERVER if you run it manually? — chepner
– chepner, Commented Feb 18, 2014 at 14:18

lurker · Accepted Answer · 2014-02-18 14:32:32Z

5

In this case, the "problem" is that ntpdc sends the timeout message to standard error, not standard out, so grep doesn't see it on the input of the pipe. You can remedy by routing standard error of the ntpdc command to standard output:

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

edited Feb 18, 2014 at 14:32

answered Feb 18, 2014 at 14:24

lurker

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