elisp parse output of asynchronous shell command - shell

I have a simple elisp interactive function that I use to launch a Clojure repl.
(defun boot-repl ()
(interactive)
(shell-command "boot repl wait &"))
It opens an *Async Shell Command* buffer, and after a while the following text appears :
nREPL server started on port 59795 on host 127.0.0.1 - nrepl://127.0.0.1:59795
Implicit target dir is deprecated, please use
the target task instead. Set BOOT_EMIT_TARGET=no to disable implicit
target dir.
I would like to monitor the output of this command to be able to parse the port ("59795" in this example).
Even just the first line (in the case without warnings) would be alright.
This way I could be able to use another command to connect to the Clojure REPL waiting for me.
I cannot use shell-command-to-string as the command does not return and it blocks emacs forever (boot repl wait is supposed to last for my whole programming session, possibly more).
There may be something easy to do with cider also, but I haven't found it.
So, how do I parse the result of an asynchronous bash command in Elisp ?
Alternatively, how can I set-up Cider to launch this REPL for my and connect to it ?

To answer the question directly, you can definitely parse the output of an asyncronous shell command, using start-process and set-process-filter:
(let ((proc (start-process "find" "find" "find"
(expand-file-name "~") "-name" "*el")))
(set-process-filter proc (lambda (proc line)
(message "process output: %s" line))))
(Docs for filter function)
However, note that line above is not necessarily a line, and may include multiple lines or broken lines. Your filter is called whenever the process or emacs decides to flush some ouput:
...
/home/user/gopath/src/github.com/gongo/json-reformat/test/json-reformat-test.el
/home/user/gopath/src/github.com/gongo/json-reformat/test/test-
process output: helper.el
In your case, this could mean that your port number might be broken into two separate process-filter calls.
To fix this, we can introduce a line-buffering and line-splitting wrapper, which calls your filter for each process output line:
(defun process-filter-line-buffer (real-filter)
(let ((cum-string-sym (gensym "proc-filter-buff"))
(newline (string-to-char "\n"))
(string-indexof (lambda (string char start)
(loop for i from start below (length string)
thereis (and (eq char (aref string i))
i)))))
(set cum-string-sym "")
`(lambda (proc string)
(setf string (concat ,cum-string-sym string))
(let ((start 0) new-start)
(while (setf new-start
(funcall ,string-indexof string ,newline start))
;;does not include newline
(funcall ,real-filter proc (substring string start new-start))
(setf start (1+ new-start)));;past newline
(setf ,cum-string-sym (substring string start))))))
Then, you can safely expect your lines to be whole:
(let* ((test-output "\nREPL server started on port 59795 on host 127.0.0.1 - \nrepl://127.0.0.1:59795 Implicit target dir is deprecated, please use the target task instead. Set BOOT_EMIT_TARGET=no to disable implicit target dir.")
(proc (start-process "echo-test" "echo-test" "echo" test-output)))
(set-process-filter proc (process-filter-line-buffer
(lambda (proc line)
(when (string-match
"REPL server started on port \\([0-9]+\\)"
line)
(let ((port (match-string 1 line)))
;;take whatever action here with PORT
(message "port found: %s" port)))))))
Finally, I'm not familiar with cider but this kind of low-level work probably belongs in an inferior-type mode and has probably already been solved.

shell-command
allows to name optional output- and error-buffers. Than the error should appear inside the latter and not clutter the output any more.

A better answer to the other one I provided is to simply use cider as you suggested:
(progn
(package-refresh-contents)
(package-install 'cider)
(cider-jack-in))

Related

Emacs: How to enable highlighting breakpoints in a text terminal (emacs -nw)

Emacs doesn't show breakpoints in text mode.
I tried integrating the suggestions here and here, but failed (I am not a lisp programmer).
I tried:
(require 'gdb-mi)
(setq default-text-properties '(foo 1111))
(defun set_breakpt_cmds ()
"set breakpoint and indicate on editor"
(interactive)
(gud-break)
(gdb-put-breakpoint-icon "false" (get-text-property 1 'foo)))
(global-set-key (kbd "<f12>") 'set_breakpt_cmds)
The resulting error is
Wrong number of arguments: (lambda (arg) "Set breakpoint at current line." (interactive "p") (if (not gud-running) (gud-call "dbstop \
at %l in %f" arg))), 0
Note: A similar issue is this (following this). However the solution there doesn't fit me because I would like to be able to call the fix from .emacs file. This way it is easier to duplicate my emacs configuration when I setup a new linux box.
Thanks
The error you get comes from the fact that gud-break expects an argument (which isn't used), so just use (gud-break 1).
The message reads as follow:
the error is of kind wrong number of arguments
when calling (lambda (arg) ...) (where we see that exactly one argument is expected)
and it was called with 0 arguments.

How would I make this Racket code DRYer?

I'm porting a Python script to Racket as a learning experience, and I have this function:
(define (check-status)
(define git [find-executable-path "git"])
(define-values (ckot out in err)
(subprocess #f #f #f git "checkout" "-q" "master"))
(define-values (local lout lin lerr)
(subprocess #f #f #f git "rev-parse" "#"))
(define-values (remote rout rin rerr)
(subprocess #f #f #f git "rev-parse" "#{u}"))
(define-values (merge-base mbout mbin mberr)
(subprocess #f #f #f git "merge-base" "#" "#{u}"))
(display-lines (port->lines mbout))
(define ports '(ckot out in err local lout lin lerr remote rout rin rerr merge-base mbout mbin mberr))
(map (lambda (x)
(cond ((input-port? x) (close-input-port x))
((output-port? x) (close-output-port x)))) ports))
The problem is that it's not very DRY. Since I'm using a Lisp, and Lisp is known for being able to do crazy things, I want to know if there's a way to take all the subprocess code and extract it so I can do something like:
(define (check-status)
(define commands '(
'("checkout" "-q" "master")
'("rev-parse" "#")
'("rev-parse" "#{u}")
'("merge-base" "#" "#{u}"))
(map currently-immaginary-git-command-fn commands))
and end up with a list of the output of each command in the list of commands. How would I do this? Since I'm new to the whole Lisp/Scheme thing, I'm figuring out the syntax as I go and I'm not fully aware of the resources available to me.
First of all, good for you for wanting to come up with a cleaner solution! You're right that there's a more elegant way to do what you've attempted.
To start, using subprocess is almost certainly overkill in your particular use-case. The racket/system module provides a simpler interface that should be sufficient for your needs. Specifically, I'd use the system* function, which executes a single process with the provided arguments, then prints its output to stdout.
Using system*, it's possible to create a very general helper function that can execute a command for a particular executable and returns its output as a string.
(define (execute-command proc-name)
(define proc (find-executable-path proc-name))
(λ (args)
(with-output-to-string
(thunk (apply system* proc args)))))
This function itself returns a new function when it's called. This means that using it to call a Git command would look like this:
((execute-command "git") '("checkout" "-q" "master"))
The reason for this will become apparent shortly.
Actually looking at the implementation of execute-command, we use with-output-to-string to redirect all of the output from the system* call into a string (instead of just printing it to stdout). This is actually just an abbreviation for using parameterize to set the current-output-port parameter, but it's simpler.
With this function, we can implement check-status very easily.
(define (check-status)
(define commands
'(("checkout" "-q" "master")
("rev-parse" "#")
("rev-parse" "#{u}")
("merge-base" "#" "#{u}")))
(map (execute-command "git") commands))
Now the reason for having (execute-command "git") return a new function becomes apparent: we can use that to create a function which will then map over the commands list to produce a new list of strings.
Also, note that the definition of the commands list only uses a single ' at the beginning. The definition you provided would not work, and in fact, the ports list you defined in your original implementation is not what you'd expect. This is because '(...) is not exactly the same as (list ...)—they are different, so be careful when using them.

Why this scheme code can't resolve the first one of spoj?

The problem is here: http://www.spoj.com/problems/TEST/
And my scheme solution is:
(define (main)
(let ((line (read-line)))
(if (or
(eof-object? line)
(string=? line "42"))
(void)
(begin
(display line)
(newline)
(main)))))
(main)
It reports
runtime error (NZEC)
But I don't know why it's wrong.
You should install guile and try your code before you submit. Guile doesn't have read-line available by default. You need to add this as first line:
(use-modules (ice-9 rdelim))
So what happens is that guile post an error and return a non zero value back to the parent process, which in turns indicated the program did not terminate normally. SPOJ will then report is as NZEC.
The guile error looks like this:
sylwester#sylhp ~> guile test.scm
ERROR: Unbound variable: read-line
Whenever you get NZEC you should try to run it locally to find errors.

Emacs equivalent to VIM's `%`?

In VIM, One can use % to indicate the current filename when invoking a shell command. Can Anyone point Me in the direction of documentation showing what the equivalent is in emacs?
There isn't one. But this is Emacs! So here:
(defun my-shell-command-on-current-file (command &optional output-buffer error-buffer)
"Run a shell command on the current file (or marked dired files).
In the shell command, the file(s) will be substituted wherever a '%' is."
(interactive (list (read-from-minibuffer "Shell command: "
nil nil nil 'shell-command-history)
current-prefix-arg
shell-command-default-error-buffer))
(cond ((buffer-file-name)
(setq command (replace-regexp-in-string "%" (buffer-file-name) command nil t)))
((and (equal major-mode 'dired-mode) (save-excursion (dired-move-to-filename)))
(setq command (replace-regexp-in-string "%" (mapconcat 'identity (dired-get-marked-files) " ") command nil t))))
(shell-command command output-buffer error-buffer))
(global-set-key (kbd "M-!") 'my-shell-command-on-current-file)
You can use this whenever the minibuffer expects you to type something (caveat: does not work with ido, but obviously you can always get out of that with e.g. C-x C-f). You can also use it in regular buffers.
(defun insert-filename-or-buffername (&optional arg)
"If the buffer has a file, insert the base name of that file.
Otherwise insert the buffer name. With prefix argument, insert the full file name."
(interactive "P")
(let* ((buffer (window-buffer (minibuffer-selected-window)))
(file-path-maybe (buffer-file-name buffer)))
(insert (if file-path-maybe
(if arg
file-path-maybe
(file-name-nondirectory file-path-maybe))
(buffer-name buffer)))))
(define-key minibuffer-local-map (kbd "C-c f") 'insert-filename-or-buffername)
in my case, using the emacs 24 gui version from homebrew.... I see the filename as the 3rd item in from the bottom left corner of the (minor)-mode-bar, just above the mini-buffer.
To see where i am, using ido-mode i just do C-x C-f No config needed there.

suppress additional braces in emacs electric mode

I started using ruby-electric-mode. I like it except that I am used to closing open brackets myself (the other pairing are still useful to me). How can I make emacs suppress additional brackets when I type in the closing brackets myself? I now am manually deleting the auto-magically inserted bracket every time.
Thanks in advance,
Raghu.
It sounds like what you want is for the } to either jump to the (already inserted) }, or to simply insert a } and delete the } that was inserted earlier by the electric mode.
This code should do what you want, the choice of what to do on } is toggled by the variable my-ruby-close-brace-goto-close.
;; assuming
;; (require 'ruby)
;; (require 'ruby-electric)
(defvar my-ruby-close-brace-goto-close t
"Non-nill indicates to move point to the next }, otherwise insert }
and delete the following }.")
(defun my-ruby-close-brace ()
"replacement for ruby-electric-brace for the close brace"
(interactive)
(let ((p (point)))
(if my-ruby-close-brace-goto-close
(unless (search-forward "}" nil t)
(message "No close brace found")
(insert "}"))
(insert "}")
(save-excursion (if (search-forward "}" nil t)
(delete-char -1))))))
(define-key ruby-mode-map "}" 'my-ruby-close-brace)
It is a “customizable” setting. Run M-x customize-variable (ESCx if you do not have a Meta key) and customize ruby-electric-expand-delimiters-list.
Uncheck “Everything” and check only the ones you want to be automatically inserted. Be sure to also “Save for Future Sessions”.
If you decide that you mostly like the automatic insertions but that there are some places where you want to turn it off for a single keystroke, then use C-q (Control-q) before an open paren/bracket/brace/quote to suppress the automatic insertion of the closing mark.
Ran into the same issue. The solution I found is to:
Use autopair, which does exactly what you want. Make sure you install it.
Enable ruby-electric-mode but only for | because the rest is already taken care of.
This leads to the following code in your .emacs file:
(use-package autopair
:config (autopair-global-mode)
)
(use-package ruby-electric-mode
:init
(setq ruby-electric-expand-delimiters-list (quote (124)))
)
(add-hook 'ruby-mode-hook 'ruby-electric-mode)
This code uses use-package package, make sure you installed it (M-X list-packages, then find use-package, then i on the line, then x and restart emacs).
Also, that might interest people visiting this thread. I added this code to skip closing delimiters with TAB, it helps jumping over them. Comment out the while lines (and adjust )) to have a single TAB jump over all closing delimiters (taken from emacs board discussion):
(use-package bind-key)
(defun special-tab ()
"Wrapper for tab key invocation.
If point is just before a close delimiter, skip forward until
there is no closed delimiter in front of point. Otherwise, invoke
normal tab command for current mode.
Must be bound to <tab> using bind-key* macro from bind-key package.
Note, this function will not be called if `override-global-mode' is
turned off."
(interactive)
(defun next-char-delims (delims)
(let ((char (and (not (equal (point) (point-max)))
(string (char-after (point))))))
(when char (member char delims))))
(let ((open '("'" "\"" ")" "]" "}" "|")))
(if (next-char-delims open)
(progn (forward-char 1))
;;(while (next-char-delims open)
;; (forward-char 1)))
(call-interactively (key-binding (kbd "TAB"))))))
(if (macrop 'bind-key*)
(bind-key* (kbd "<tab>") 'special-tab)
(user-error "Must have bind-key from use-package.el to use special-tab function"))
This time, you need the bind-key package for this snippet to work.

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