Index > Shell Script Portability Notes

Base system utilities can vary across operating systems. Here's some quick notes to help with fixing issues that come up. Typically these come from scripts that assume GNU coreutils.

• sort -R—Unsupported on Mac OSX and NetBSD

  `sort -R` (a.k.a. `sort --sort=random`) isn't specified by POSIX, and you'll get wildly unexpected results on Mac OSX and NetBSD. The fastest-running solution is to install and use shuf(1), part of GNU coreutils. There are a few other good solutions here as well: Stack Overflow

• tar --exclude-from—Unsupported on OpenBSD and busybox tar(1)

  This one will break any backup scripts if you use files to store exclusion lists. Best bet is to install a different tar package. You can check if your tar supports --exclude-from by running `tar --version`. `bsdtar` and `tar (GNU tar)` will run as expected, as will NetBSD's tar(1), which doesn't support --version but you can check uname to see if you're on a NetBSD box.

• tar -J—Unsupported on OpenBSD tar(1)

  One solution is to use the next best thing: tar -j. Alternatively, you can install the xz package and pipe the archive to it via stdin for compression and redirect the result, `tar -f - <files> | xz --stdout > <archive.tar.xz>`

• uname -m—Prints amd64 on *BSD, x86_64 on Linux

• \b regex word boundaries—Unsupported on OpenBSD grep(1)

  \b as a word boundary likely originated with Perl regular expressions, and are supported everywhere, except for OpenBSD. Instead use POSIX word boundaries [[:<:]] and [[:>:]] to match the beginning and ending of words, respectively.