Command line tips & tricks

One thing that (irrationally) bugs me is seeing "grep -v grep"; e.g.

ps -ef | grep java | grep -v grep

So I use this character class trick that someone showed me years ago:

ps -ef | grep [j]ava

It'll also work anywhere else that regex can be used, like awk:

ps -ef | awk '/[j]ava/ {print $2}'

Yes, pgrep will do this, but I work a lot on AIX, which doesn't have pgrep.

Also, for parallel execution, you can use xargs and nproc if parallel is not installed/available.

ls -1 *.flac | xargs -P $(nproc) -n1 -I{} oggenc "{}"

Using nproc will match the number of logical CPUs in your machine, but you could use more or less if you want.