The 'fgrep' and 'egrep' didn't throw errors, it would just send a warning to standard error before behaving as expected.
Those commands were never standardized, and everyone is better off using 'grep -F' and 'grep -E' respectively.
Noted without comment. Except to say that I've had multiple scripts of my own break via "just" discovering garbage in the output streams.
> Those commands were never standardized
"Those commands" were present in v7 unix in 1979!
The only place that that doesn't support 'grep -E' and 'grep -F' nowadays is Solaris 10. But if you are still using that you will certainly run into many other missing options.
[1] https://pubs.opengroup.org/onlinepubs/007908775/xcu/egrep.ht... [2] https://pubs.opengroup.org/onlinepubs/007908775/xcu/fgrep.ht...
The deprecation argument is at least... arguable. It was indeed retired from POSIX. But needless deprecation is itself a smell in a situation where you can't audit all the code that uses it. Don't do that. It breaks stuff. It broke the updates in the linked article too. If you have an API, leave it there absent extremely strong arguments for its removal.