Work the Shell - Still Parsing the Twitter Stream

 in
How do you keep track of which tweets you've already answered?
But What Have We Already Seen?

The answer isn't that hard. The stream is newest to oldest, and the message ID values are assigned sequentially by the server, so all we need to do is cache the most recent message ID we've seen after we have answered all queries. Then, on subsequent invocations, compare each query ID to the most recent we've answered. If they're greater, we need to answer them. If not, we've already done so. Like this:

if [ "$id" == "$previouslatestid" -o $answered -eq 1 ] ; then
  echo "already answered query \"$msg\" from $name: skipped"
  answered=1
else
  ...

The previouslatestid is what's cached. We'll also capture the most recent ID of the current wave of queries like this:

if [ -z "$latestid" ] ; then
  latestid=$id        # store most recent ID
fi

Of course, there are a few more steps. We need to grab the cached value at the beginning of the script:

if [ -f "$lastidcache" ] ; then
  previouslatestid="$(cat "$lastidcache")"
else
  previouslatestid="0"
fi

And, we need to save it at the end:

echo $latestid > "$lastidcache"

That's it. I've run out of space, but the full script is available at ftp.linuxjournal.com/pub/lj/listings/issue191/10695.tgz. Next month, we'll polish it a bit and see what fun we can have with a tweetbot!

Dave Taylor has been hacking shell scripts for a really long time. He's the author of the popular Wicked Cool Shell Scripts and can be found on Twitter as @DaveTaylor and more generally at www.DaveTaylorOnline.com.

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Dave Taylor has been hacking shell scripts for over thirty years. Really. He's the author of the popular "Wicked Cool Shell Scripts" and can be found on Twitter as @DaveTaylor and more generally at www.DaveTaylorOnline.com.