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Editorial Team
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Asked: 2026-05-23T02:37:27+00:00

I want to get the first string that matches my regular expression. For example

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I want to get the first string that matches my regular expression.
For example I have the String

RCPT from unknown[211.147.3.74]: 450 4.7.1 Client host rejected: cannot find your hostname, [211.147.3.74];

and my script looks like this:

IP=`echo $LINE | grep -E -o --max-count=1 '(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)'`

echo $IP

As result I get

211.147.3.74 211.147.3.74

But I would like to get the IP only once. I tried ‘grep –max-count=1’ but there are still two ip’s.

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1 Answer

  1. Editorial Team
    LINE='RCPT from unknown[211.147.3.74]: 450 4.7.1 Client host rejected: cannot find your hostname, [211.147.3.74];'
ipn='(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)'
IP=`echo $LINE | grep -E -o "$ipn\.$ipn\.$ipn\.$ipn" | head -1`
echo "$IP"

    or from here

    echo "$LINE"  | perl -MRegexp::Common=net -ne '/($RE{net}{IPv4})/ and print "$1\n"'
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