At 11:35 AM 2/19/2008, Paul Schmehl wrote:
I could do this in perl easily, but I'm trying to force myself to learn shell scripting better. :-)

I'm parsing a file to extract some elements from it, then writing the results, embeded in long strings, into an output file.

Here's the script:

cat file.1 | cut -d',' -f9 | sort | uniq > file.nicks

(read line; echo "alert ip \$HOME_NET any -> \$EXTERNAL_NET any (msg:\"JOIN $line detected\"; classtype:trojan-activity; content:\"JOIN\"; content:$line; sid:2000001; rev:1;)"; while read line; do echo "alert ip \$HOME_NET any -> \$EXTERNAL_NET any (msg:\"JOIN $line detected\"; classtype:trojan-activity; content:\"JOIN\"; content:$line; sid:2000001; rev:1;)"; done) < file.nicks > file.rules

The result is a file with a bunch of snort rules in it (I can't provide the actual data because it's sensitive.)

The rules look like this:
alert ip $HOME_NET any -> $EXTERNAL_NET any (msg:"JOIN "channel" detected"; classtype:trojan-activity; content:"JOIN"; content:"channel"; sid:2000001; rev:1;) alert ip $HOME_NET any -> $EXTERNAL_NET any (msg:"JOIN "channel2" detected"; classtype:trojan-activity; content:"JOIN"; content:"channel2"; sid:2000001; rev:1;)

Once this file is created (or ideally *while* it's being created!) I need to increment the sid numbers. The first one is 2000001. The second needs to be 2000002, and so forth. I don't know the total number of lines ahead of time, but it's easy enough to get after the file is created. (wc -l file.rules | awk '{print $1}')

Is there a way to do this in shell scripting? In perl I'd use a for loop and vars, but I'm not sure how to solve this problem in shell scripting.

In pseudo code I would do:

COUNT=`wc -l file.rules | awk '{print $1}'`
LAST_SID=$((2000000 + COUNT))
for (i=2000001; i >= ${LAST_SID}; i++) {
   sed 's/2000001/${i}/g < file.rules > rules.new'
}

Similar to what other's have offered:

for i in `cat file.rules`;do
        sed 's/2000001/${i}/g >> rules.new;
done

        -Derek

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