In practice, sticking to POSIX is really hard in the modern day. In particular, there's really no POSIX happy way to parse JSON (yes, you can do it in pure awk, but bleah). So mostly my portable environments depend on `jq`, which is used mostly to parse JSON and turn it into something I can munge with awk.
The other thing POSIX doesn't have is the latest in regular expressions, so I usually want the GNU egrep from binutils - that's generally easy to install.
@ed_packet @sungo Pedantic side note, since POSIX is being talked: GNU grep is its own package and not part of binutils, and POSIX 2008 mandates that ‘grep -E’ support EREs (but does not mandate supporting invocation as ‘egrep’, considering it “historical”). 📕
Of course if you want PCRE or something that's a different story!
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