Solaris 10 Well, it is true that Solaris 10 /bin/sh does not understand $(...).
"Configure scripts will automatically locate a shell that supports Yes, I saw that too. Which is fine for autoconf's configure scripts (and I'm very glad they're doing it), but what about when config.{guess,sub} are executed from something other than autoconf-generated configure scripts? Autoconf is not the whole world, by a long shot. https://mywiki.wooledge.org/BashFAQ/082 Thanks for the pointer. I remain completely unconvinced. The various points are merely described as things like "non-obvious ... convenient ... nicer ..." In other words, there is no technical reason to force out `...` for $(...), just cosmetic reasons. Sure, I wouldn't recommend `...` in a primer for shell programming, but config.* is hardly that. It is perfectly possible to use `...` correctly and portably, and an awful lot of work has gone into doing so. I don't know of any problems with the use of `...` in config.* (or autoconf for that matter). For something as fundamental as config.*, the switch seems a bad idea to me. FWIW ... I doubt it's an inviting prospect for config.* to also try to find and re-execute with a good shell, though that's another option. Thanks for considering, Karl