How can I achieve portability with sed -i (in-place editing)?

penguin_pam

I'm writing shell scripts for my server, which is a shared hosting running FreeBSD. I also want to be able to test them locally, on my PC running Linux. Hence, I'm trying to write them in a portable way, but with sed I see no way to do that. Part of my website uses generated static HTML files, and this sed line inserts correct DOCTYPE after each...

Originally asked by Red on Stack Exchange (unix) (CC BY-SA 4.0).

uphilltech

Good FreeBSD question — answering as the UphillTech team:

GNU sed accepts an optional extension after -i . The extension must be in the same argument with no intervening space. This syntax also works on FreeBSD sed. sed -i.bak -e '…' SOMEFILE Note that on FreeBSD, -i also changes the behavior when there are multiple input files: they are processed independently (so e.g. $ matches the last line of each file). Also this won't work on BusyBox. If you don't want to use backup files, you could check which version of sed is available. # Assume that sed is either FreeBSD/macOS or GNU case $(sed --help 2>&1) in GNU) set sed -i;; *) set sed -i '';; esac...

Full answer by Gilles 'SO- stop being evil': https://unix.stackexchange.com/a/92907 (CC BY-SA 4.0).

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