You can also use append empty string directly after -i to make sed -i work on both GNU and BSD sed:

sed -i'' 's/a oneshot/an addrfetch/g' src/chainparams.cpp

I want to work on this, but I think it is good to recommend people to do the above for portability for now.

@Z5483 hi! thanks for taking a look & opening a PR!

I tried this trick out locally (macOS), but got an error... actually, I'm getting different errors on each try 👀
(but doing -i '' is working fine)

but I see you've opened a patch to update the script, so I'll check that out :)

@Z5483 Thanks for working on this! I've ran into some scripted-diff issues as well, and I'm very excited to see that you're improving it :)

@amitiuttarwar I'm a MacOS user as well, and I ran into the following issue; did you ever encounter this as well?

$ ./test/lint/commit-script-check.sh 85165d4~..85165d4
sed: 1: "/^-BEGIN VERIFY SCRIPT- ...": unexpected EOF (pending }'s)
Error: missing script for: 85165d4332b0f72d30e0c584b476249b542338e6
Failed

I fixed it locally by installing gsed and creating a symbolic link. But do you think it would make sense to add something like the following to help future MacOS users?

After making this change, here's the new output:

$ ./test/lint/commit-script-check.sh 85165d4~..85165d4
sed: 1: "/^-BEGIN VERIFY SCRIPT- ...": unexpected EOF (pending }'s)
Error: Incompatible version of sed; MacOS users should install gsed
Failed

I'm signing up for this task (if still open) because @bliotti wants me to work on it as "I'm way overdue for a bitcoin commit" as a Jimmy Song Alumni, using my public face here.

@bitkarrot Awesome! Looks like a good one. @amitiuttarwar or @Z5483 where does this one stand? We would like to pick this one up if still available. Thanks!

Feel free to work on this. I scrapped my PR because I didn't put time into it so it's horrible. I'm busy with schools for the rest of the school year so I don't think I will pick this up again anytime soon. I hope you guys can produce something better than mine.

Catching sed syntax usage that leads to unexpected results is not a low hanging fruit I guess :)

Maybe you should pimp your own script like so:

kernel_name="$(uname -s)"

case "${kernel_name}" in
    Linux*)     sed_option='-i'
                ;;
    Darwin*)    sed_option='-i ""'
                ;;
    *)          echo "Unknown kernel name: '${kernel_name}'"
                exit 1
esac

sed $sed_option 's/a oneshot/an addrfetch/g' src/chainparams.cpp

With that, you can define all specialities needed for different environments. You could pimp it even more like checking the the version etc.

Maybe you could create a PR to add this as a template to https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#suggestions-and-examples