:external "ls"and then eval the function again. (This is necessary so that eshell doesn't fall back to the system's `ls' command when it gets confused.) Then open `eshell' and run:
ls '-I*.el'Instead of what you'd expect (a directory listing that ignores Emacs Lisp files), instead you get a directory listing of *all* the files in the long listing format. That's because `eshell-eval-using-options' assumes that all the characters after the "-" are names of short options, rather than a single short option followed by its value. You can see a similar problem with:
ls '--ignore=*.el'In this case, `eshell-eval-using-options' looks for an option named "ignore=*.el" instead of an option named "ignore" followed by its value.
I've attached a patch with tests to fix this and use the POSIX/GNU argument conventions, supporting both the above cases. However, I should mention that this is a slightly incompatible change. A small number of existing eshell commands work like `ls -I', and their behavior is now a bit different. Previously, you could do the following,
ls -Ia '*.el'to list all the files in a directory, excluding Emacs Lisp files. Now, you have to spell that as:
ls -aI '*.el' # or... ls -aI'*.el'I think that's ok though, since I can't imagine anyone *wanting* the old behavior. It surprised me quite a bit when I stumbled across it, and worse, it only crops up sometimes, since eshell transparently falls back to the real commands when it gets confused.
For completeness, the following commands+options are affected: sudo -u du -d ls -I [1] https://www.gnu.org/software/libc/manual/html_node/Argument-Syntax.html
0001-Follow-POSIX-GNU-argument-conventions-for-eshell-eva.patch
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