That didn't sound right to me, but I looked it up, and you're right. The scripts we're discussing were written in 2002 [1], so the time-appropriate version is

That didn't sound right to me, but I looked it up, and you're right. The scripts we're discussing were written in 2002 [1], so the time-appropriate version is POSIX-2001 (Issue 6). [1]: https://github.com/freebsd/freebsd/commit/55d0b8395514ae4055e7af8e4e9812637dbcc463 https://github.com/freebsd/freebsd/commit/55d0b8395514ae4055... But you don't have to take my word for it: I've paste-bin'ed the entirety of what POSIX-2001 had to say about shell built-ins (in general, I didn't include man-pages for individual built-ins): https://lukeshu.com/dump/posix-2001-builtins.txt https://lukeshu.com/dump/posix-2001-builtins.txt As for whether that's still true today, looking at POSIX-2008 (Issue 7), 2013 edition (I don't have a copy of the 2016 edition handy), none of that has changed.