Shell Programming and Scripting

Hi,
I have one script, which is tailing from a log file. And I want to separate the output in different files based on the timestamp. Something like that:

Code:

./script.sh >> log_`date '+%Y%m%d%H'`.log

When I start the script it creates file, e.g. log_2013042314.log, and it is appending the output from the tail command. But once the hour is changed it stops. And in that case, when hour is changed, I would like to continue creating new file log_2013042315.log. Any ideas how can I do that?

Thanks!

Here is a way to change the name of the log file:

Code:

log_file=log_`date '+%Y%m%d%H'`.log
old_hour=`date '+%H'`

while sleep 10; do
  new_hour=`date '+%H'`
  if [ $new_hour -ne $old_hour ]; then
    log_file=log_`date '+%Y%m%d%H'`.log
    old_hour=$new_hour
  fi
done

But it seems problematic stopping and starting the tail -f command. What if you just periodically create your separate hourly files in a batch process, possibly at the end of the day? Besides being easier to do, that would also seem a more reliable way to ensure none of the records end up in the wrong hourly file.

do you need to get log every 1 second , use this %Y%m%d%H%S

Code:

./script.sh >> log_`date '+%Y%m%d%H%S'`.log

Thanks Hanson44! It works OK, I just change it to:

Code:

i=1
while [ i=1 ]

I'm really glad it's working. And your addition makes it better. I do have one little suggestion. I would say:

[ 1 -eq 1 ] instead of [ i=1 ] and leave off the line where i is initialized.

Your syntax works, so in a way it's "right". But I have never seen [ i=1 ] syntax. It really surprised me and made me scratch my head, and I don't understand exactly why it works.

The other choice would be to say [ $i = 1 ] but then you might as well just say [ 1 -eq 1 ]

Uppps, typo, my mistake....actually it is:

Code:

[ $i=1 ]

At the end I changed it to:

Code:

[ 1 -eq 1 ]

Thanks again!

The test/[ command treats a single non-empty string argument as true, and a single empty string argument as false. i=1 is parsed as a single non-empty string.

For an infinite loop, I think it's best to use either while :; do ... or while true; do .... I believe it makes the intent clearer than testing something against itself.

apenkov:

With regard to the script, I hope this isn't something critical, because, as hanson44 points out, it is possible for entries to land in the wrong file. The batch processing suggestion is a much better idea.

Also, since it seems that the full script has not been posted, I can't say for certain what is going on, but, if the while-loop is spending most of its time checking for the start of a new hour, that's a job that is probably best handled by cron.

Regards,
Alister