illumos gate

I'm not sure what I can do about it - getopt_long's "optional argument" won't accept '-i ""' (I described it all in #586, and Garrett's decision was to be GNU sed compatible).

Then I'll just back the cset out of our tree. Having our current scripts not break is more important to me than having future scripts be more GNU compatible.

You could change sed invocations to have just '-i'...

That misses the point entirely. Things should not break, especially without as much as a flag day.

Digging through every script we have looking for sed -i "" is a great deal of work compared to backing out a changeset that introduces a feature we neither use nor want.

The error we get from sed in this case is from all the way down in mf_gets at http://src.illumos.org/source/xref/illumos-gate/usr/src/cmd/sed/main.c#401 though. How's that the case if getopt_long can't cope?

I can't see how -i of explicit "" (that is, optarg is "") and -i with no arg (that is, optarg == NULL, and we assign inplace = "") differ?

The problem here is in how getopt_long handles optional arguments. Optional argument should follow the option without any blanks, so -i"" will work, but in the -i "" case "" is assumed to be the 'script' or the 'file', returning an error..