awk

Delete lines using awk

November 5, 2021 by Ulysses

Here’s how to delete a line from a file using awk.

awk '!/Redhat/' sample.txt > sample.tmp && mv sample.tmp sample.txt

The command above looks for ‘Redhat’ in a file and removes that line from the file.

You can add the line in the crontab to run at reboot if you like.

crontab -e

@reboot awk '!/Redhat/' sample.txt > sample.tmp && mv sample.tmp sample.txt

AWS S3 LS Recursive

April 5, 2020 by Ulysses

Here’s how to list S3 files recursively.

aws s3 ls s3://mybucket --recursive | awk '{print $4}'

By default, the results display date, time, disk size and filename. Use awk to display the filename only.

Here’s a nice command to get rid of line duplicates in a file. I’m sending the output to a temporary file then renaming it back to the original file. The reason is, it’s probably not a good idea to overwrite a file that you are editing. It’s much safer to send the output to another file.

$ awk '!seen[$0]++' backup.sh > backup01.sh
$ mv backup01.sh backup.sh