Enable Flycheck for KSH on Linux
Flycheck is a great Emacs extension for on-the-fly syntax check. It is easy to
configure, use, and extend. With shellcheck as the backend, it worked perfectly
for my shell scripts until recently. The other day, I was not able to enable
flycheck for a shell script. After some test, it is clear that flycheck only
cannot handle ksh scripts. Luckily, the code of
flycheck.el was very easy to
follow. After digging into it, I soon figured out the root cause and a simple
The root cause is that, when using shellcheck as backend, flycheck supports ksh88 while ksh are mapped to pdksh (public domain ksh). Furthermore, as the code snippet indicates, this issue occurs only on Linux boxes.
;; in flycheck.el (defconst flycheck-shellcheck-supported-shells '(bash ksh88 sh zsh) "Shells supported by Shellcheck.") ;; in sh-script.el (defcustom sh-alias-alist (append (if (eq system-type 'gnu/linux) '((csh . tcsh) (ksh . pdksh))) ; <----- OOPS ;; for the time being '((ksh . ksh88) (bash2 . bash) (sh5 . sh))) ;; ... )
The "fix" is quite straightforward. And, it doesn't involve any modification of
flycheck. Instead, I simply customize the
sh-alias-alist by putting the
following lines into my Emacs init file.
(when (eq system-type 'gnu/linux) (setq sh-alias-alist '((csh . tcsh) (ksh . ksh88) ; flycheck doesn't handle pdksh (bash2 . bash) (sh5 . sh))))
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