How to use grep to reverse search files in a folder

Question

I'm trying to create a script which will find missing topics from multiple log files. These logfiles are filled top down, so the newest logs are at the bottom of the file. I would like to grep only the last line from this file which includes UNKNOWN_TOPIC_OR_PARTITION. This should be done in multiple files with completely different names. Is grep the best solution or is there another solution that suits my needs. I already tried adding tail, but that doesn't seem to work.

missingTopics=$(grep -Ri -m1 --exclude=*.{1,2,3,4,5} UNKNOWN_TOPIC_OR_PARTITION /app/tibco/log/tra/domain/)

Answer 1

You could try a combination of find , tac and grep :

find /app/tibco/log/tra/domain -type f ! -name '*.[1-5]' -exec sh -c \
  'tac "$1" | grep -im1 UNKNOWN_TOPIC_OR_PARTITION' "sh" '{}' \;

tac prints files in reverse, the -exec sh -c SCRIPT "sh" '{}' \; action of find executes the shell SCRIPT each time a file matching the previous tests is found. The SCRIPT is executed with "sh" as parameter $0 and the path of the found file as parameter $1 .

If performance is an issue you can probably improve it with:

find . -type f ! -name '*.[1-5]' -exec sh -c 'for f in "$@"; do \
  tac "$f" | grep -im1 UNKNOWN_TOPIC_OR_PARTITION; done' "sh" '{}' +

which will spawn less shells. If security is also an issue you can also replace -exec by -execdir (even if with this SCRIPT I do not immediately see any exploit).