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Call rx from eshell with rx to write the regexp

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But `rx` outputs Emacs regular expressions. The pcre2el project can
convert that for us.
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Howard Abrams 2022-10-01 23:40:42 -07:00
parent fbdcce4d96
commit 2294abe9d9
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@ -287,6 +287,30 @@ Why not be able to read a buffer and use it as the start of a pipeline?
args "\n"))
#+end_src
Perhaps we should add this feature to eshell’s version of [[help:eshell/cat][cat]].
** Regular Expressions
I think using the [[help:rx][rx]] macro with applications like =grep= is great reason why =eshell= rocks. Assuming we can’t remember cryptic regular expression syntax, we could look for a GUID-like strings using =ripgrep= with:
#+begin_src sh
$ rg (rx (one-or-more hex) "-" (one-or-more hex))
#+end_src
The problem with this trick is that =rx= outputs an Emacs-compatible regular expression, which doesn’t always match regular expressions accepted by most applications.
The [[https://github.com/joddie/pcre2el][pcre2el]] project can convert from a Lisp regular expression to a [[http://www.pcre.org/][PCRE]] (Perl Compatible Regular Expression), which is accepted by [[https://github.com/BurntSushi/ripgrep][ripgrep]].
#+begin_src emacs-lisp
(use-package pcre2el
:straight (:host github :repo "joddie/pcre2el")
:config
(defmacro prx (&rest expressions)
"Convert the rx-compatible regular EXPRESSIONS to PCRE.
Many shell applications accept Perl Compatible Regular Expressions."
`(rx-let ((integer (1+ digit))
(float (seq integer "." integer))
(time (seq digit (optional digit) ":" (= 2 digit) (optional ":" (= 2 digit))))
(date (seq (= 2 digit) (or "/" "-") (= 2 digit) (or "/" "-") (= 4 digit)))
(ymd (seq (= 4 digit) (or "/" "-") (= 2 digit) (or "/" "-") (= 2 digit)))
(guid (seq (= 8 hex) "-" (= 3 (seq (= 4 hex) "-")) (= 12 hex))))
(rxt-elisp-to-pcre (rx ,@expressions)))))
#+end_src
The =prx=
** Piper
My [[https://gitlab.com/howardabrams/emacs-piper][piper]] project seems to like a good match with eshell. For instance, typing =piper= in eshell with a file or a command, and the output from that goes into a Piper buffer, where standard Emacs commands can filter, sort or otherwise alter that output. Then, closing it and calling =piper= in eshell without arguments outputs that buffer … to use as part of a pipe or something.
#+begin_src emacs-lisp