So regular clojure repl works fine, (read-line) collects input, then echos it. Using lein repl though, never echoes any input characters, nor does it ever allows me to return from any stdin reading commands.
I'm sure it has something to do with rebinding in, but was wondering if there is a workaround/fix?
Thanks.
This is due to a bug in ant; it prevents the stdin stream from the subprocess it launches from being used. But the telnet trick should work since lein repl launches a socket repl server; it works fine here.
Connect to the REPL via telnet.
$ lein repl
REPL started; server listening on localhost:63849.
user=>
[1]+ Stopped lein repl
$ telnet localhost 63849
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
user=> (read-line)
hello
"hello"
user=>
This works for me now:
Wrap your read-line calls with the macro with-read-line-support which is in ns swank.core [since swank-clojure 1.4+ I believe]:
(use 'swank.core)
(with-read-line-support
(println "a line from Emacs:" (read-line)))
Thanks to Tavis Judd for the fix.
Related
How can I get readline-like (or rlwrap-like) functionality from my REPL when I use the repl function from clojure.main?
The background to this is that I'm utilizing and customizing the break function from The Joy of Clojure, First Edition. I'm using it from inside the lein repl REPL. When my "breakpoint" kicks in, the readline-like functionality of Leiningen's REPL is gone, which is kind of inconvenient. My muscle memory makes me hit ↑ followed quickly by Enter. Before I can stop myself, I've got this in my terminal:
debug=> ^[[A
CompilerException java.lang.RuntimeException: Unable to resolve symbol: in this context, compiling:(/tmp/form-init13211381000659590518.clj:1:1)
And now my REPL is stuck and I have to kill the terminal or the process to get out. I'd like very much if I could either get readline working in this second-level REPL or at least prevent this common issue from derailing my debug sessions.
You should use rebel readline, a new repl for clojure developed by bhauman the same guy who brought is figwheel.
https://github.com/bhauman/rebel-readline
It has rlwrap features, syntax highlighting and multi line code editing all in the terminal.
I'm not sure the rlwrap utility would help there, because the inner REPL is held by the outer one. So the input is being controlled by Java code, not the rlwrap tool.
You are causing an exception since you input a wrong value. I remember, the clojure.main/repl function might take an additional argument to handle exceptions. Probably, you could handle it somehow and just print a string "wrong input value" instead. Take a look at the documentation for REPL.
Also, you may implement your own REPL for debugging. Long ago, I used to write some kind of it, here what I've got:
(defn repl []
(let [input (read)]
(if (= input 'q)
nil
(do
(try
(let [result (eval input)]
(println result))
(catch Exception e
(println e)))
(recur)))))
That function just prompts for a proper Clojure expression in an endless loop, evaluates it and prints the result. In case of a wrong input, it prints the error and carries on. To leave the REPL, input q.
Example:
(repl)
(+ 1 2) ;; 2
fsdf8 9_fsd ;; prints a stack trace
q ;; returns nil and exit
Try Emacs with Cider as your repl. When you (break) you'll be bumped out of the Cider repl and into the Emacs Minibuffer, where your standard emacs editing shortcuts (upon which readline is modeled) continue to apply.
How does one read a single keystroke from the terminal (not Swing) in Clojure?
I have tried a few things including various versions of the JLine library, but have not gotten it working (see example below).
I will happily accept a working, Unix-only (Mac, Linux, ...) example. Ideally I'd like to know how to switch buffering off for both stdin and stdout.
Here's something close:
;; project.clj dependencies:
;; [[org.clojure/clojure "1.4.0"]
;; [jline/jline "2.8"]])
(ns slosh.core
(:import [jline.console ConsoleReader])
(:gen-class))
(defn -main []
(println "start")
(let [cr (ConsoleReader.)]
(.readCharacter cr)
(println "done")))
This prints "start" but does not respond to any input except control-C.
I'm not sure how you are running this, but if you are using lein run, you will run into problems. Try using lein trampoline run.
I would link Single character console input in java/clojure but I don't seem to have enough Internet Points to do that.
Maybe also have a look at clojure-lanterna.
This is my problem:
I need run some code every time I open a new repl, searching in Google I found that I can use the file init.clj or the user.clj (with Leiningen)
This is the code I need to run:
(set! *print-length* 103)
(println "hello")
(println *print-length*)
These are the results with both of the files:
[~/project]$ lein repl
hello <- this is the println, so the file is excecuted
103 <- this is the println of *print-length* apparently change
REPL started; server listening on localhost port 20875
user=> *print-length*
nil <- but the val of *print-length* don't change
Is there something I need to do or do I have some error?
Thanks to all!
(alter-var-root #'*print-length* (constantly 103)) in ~/user.clj works for me.
As far as I know set! doesn't work outside of a binding's dynamic scope.
lein's init.clj runs in the leiningen process, not in your project process. See https://github.com/technomancy/leiningen (search for init.clj)
I am writing a text game in Clojure. I want the player to type lines at the console, and the game to respond on a line-by-line basis.
Research showed me that (read-line) is the way one is meant to get text lines from standard input in Clojure, but it is not working for me.
I am in a fresh Leiningen project, and I have added a :main clause to the project.clj pointing to the only source file:
(ns textgame.core)
(defn -main [& args]
(println "Entering -main")
; (flush) ;makes no difference if flush are commented out
(let [input (read-line)]
(println "ECHO:" input))
; (flush)
(println "Exiting -main"))
using lein run yields:
Entering -main
ECHO: nil
Exiting -main
In other words, there is no opportunity to enter text at the console for (read-line) to read.
How should I get Clojure to wait for characters and newline to be entered and return the corresponding string?
(I am using GNOME Terminal 2.32.1 on Linux Mint 11, Leiningen 1.6.1.1 on Java 1.6.0_26 Java HotSpot(TM) 64-Bit Server VM, Clojure version 1.2.1.)
Update: If I run lein repl, I can (println (read-line)), but not when I have a -main function and run using lein run.
Try "lein trampoline run". See http://groups.google.com/group/leiningen/browse_thread/thread/a07a7f10edb77c9b for more details also from https://github.com/technomancy/leiningen:
Q: I don't have access to stdin inside my project.
A: There's a problem in the library that Leiningen uses to spawn new processes that blocks access to console input. This means that functions like read-line will not work as expected in most contexts, though the repl task necessarily includes a workaround. You can also use the trampoline task to launch your project's JVM after Leiningen's has exited rather than launching it as a subprocess.
I have had similar problems and resorted to building a jar file and then running that.
lein uberjar
java -jar project-standalone.jar
It's a bit slower, though it got me unstuck. An answer that works from the repl would
be better
Wrap your read-line calls with the macro with-read-line-support which is now in ns swank.core [since swank-clojure 1.4+ I believe]:
(use 'swank.core)
(with-read-line-support
(println "a line from Emacs:" (read-line)))
Thanks to Tavis Judd for the fix.
You can use read and use a string as input.
Not sure about the lein aspects of the problem, but definitely in emacs it is impossible to make stdin work. However, if you want to get text from the user, you can easily do it using a JOptionPane like this code from my little tic-tac-toe program:
(defn get-input []
(let [input (JOptionPane/showInputDialog "Enter your next move (row/column)")]
(map #(Integer/valueOf %) (.split input "/"))))
I'm trying to exit the REPL.
I use (. System exit 0) or (System/exit 0), but that causes an error:
Exception in thread "Thread-3" java.lang.RuntimeException: java.lang.IndexOutOfBoundsException
Is there another way to exit the REPL? How I can resolve this error?
You can send the 'end-of-file' character.
You can just press ctrl-d (*nix) or ctrl-z (Windows) to exit the REPL.
My answer is now 10 years old and was given a context of less understanding (although I think I shared the same confusion as the original asker so it kind of works).
(System/exit 0) does indeed exit the whole JVM - that might be what you want "to exit the REPL" but not necessarily. Clojure and it's REPL are designed to run in a multi-threaded environment and you can even have multiple REPLs connected to the same process. Obviously exiting the JVM is not what you want if you want to exit a REPL in an otherwise continuing process.
Original answer below:
It looks like you have a different problem in your code.
The way to exit the repl is:(System/exit 0)
The alternative syntax (. System exit 0) also works.
You can test this from a clean repl started with:
java -cp clojure.jar clojure.main -r
The exception you get would seem to indicate an error in some indexed lookup before your code gets to the intended exit point, apparently on a different thread.
The problem with (System/exit 0) is that it kills the whole JVM. The real question is how to programmatically exit just the current repl, and return to whatever function launched that repl.
Here is a convenient hack:
(clojure.main/repl
; Exit the repl whenever the user enters "exit" at the prompt.
:read (fn [request-prompt request-exit]
(let [form (clojure.main/repl-read request-prompt request-exit)]
(if (= 'exit form) request-exit form))))
clojure.main/repl repeatedly calls a a reader, by default repl-read, to get one form at a time. One of the arguments to the reader is a special sentinel object that the reader is supposed to return when there are no more forms to be read. The default reader, repl-read, returns the sentinel value only on EOF. At the repl-read prompt, you do not have access to the sentinel object, so you cannot return it to tell the evaluator that you have finished entering forms. By installing your own reader, you can check for a particular form -- e.g., the symbol exit -- and return the sentinel object whenever this form is read, thus indicating to the evaluator that you are ready to exit the repl, without actually killing the entire VM.
i just wanted to exit my REPL and landed here.
This seems to be a question that comes to everyones mind when starting to do first steps in the Clojure REPL. And of course I did not read the start-up message. The answer for my Clojure 1.7.0 is (exit) or (quit) or Control-d as stated in other replies.
nREPL server started on port 49276 on host 127.0.0.1 - nrepl://127.0.0.1:49276
REPL-y 0.3.7, nREPL 0.2.10
Clojure 1.7.0
Java HotSpot(TM) 64-Bit Server VM 1.8.0_72-b15
Docs: (doc function-name-here)
(find-doc "part-of-name-here")
Source: (source function-name-here)
Javadoc: (javadoc java-object-or-class-here)
Exit: Control+D or (exit) or (quit)
Results: Stored in vars *1, *2, *3, an exception in *e
user=> (exit)
Bye for now!
You may use the following key combination to exit Cider REPL in emacs: C-c C-q
If you install "lein" then it's exit or quit like this:
$ lein repl
...
user=>exit
Bye for now!
On Mac, use CTRL + C twice, see:
to exit the repl:
If you're running the repl from the command line then (as Sean mentions) ctrl-d
if you're running it from slime then Alt-x slime-quit-lisp should do it.
if you're running it from eclipse then i'm not sure there is a clean way to exit use the little red button.
today I have the answer, this is what I need
(import ('java.lang.management ManagementFactory)
(use 'clojure.contrib.shell)
(defn process-pid [] (let [m-name (.getName (ManagementFactory/getRuntimeMXBean))] (first (.split m-name "#"))))
(defn exit (sh "kill" (process-pid))
In Windows (tested on Windows 7 x64), using the standard command shell (cmd.exe), the ctrl-Z (followed by the enter key) character appears to be the end-of-file indicator, it dropped me out of the REPL back to the command prompt. I suspect that this will also work equivalently in Windows PowerShell, would someone who is familiar with it please test and confirm...
Note also that this is for the stock Clojure REPL - if you are running the Datomic shell (which appears to be an instance of a Java Beanshell), enter "quit();"...
HTH.
On Clojure 1.10.2 installed on Linux
(. System exit 0)