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I need to create a Java command line to that will be invoked remotely on a server. It will need to:

  • Read "lines" of text from the user.
  • Recognise if the user presses the "tab" key to facilitate auto-complete.
  • Recognise if the user presses the "up/down" keys for history.

Before I go off and roll my own, Is anyone aware of a Java library that might facilitate all or part of this?

i.e. From the command line in ssh it might look like this:

bob> java -jar MyTool.jar

MyTool Started.
Please enter command:

> server1 startup
server starting...
server started

> server2 load accounts
Done

> server3 shutdown
Complete

>quit

Jay
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  • To help with your googling, the keyword you are looking for is "readline", which is the C library that powers the Bash command line, among others. I found you a couple of Java readline-like libraries in my answer, below. You might probably find some others that better suit your needs. – Edward Samson Sep 26 '12 at 06:39

7 Answers7

6

Check out JReadline and jline2.

Edward Samson
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5

Update: picocli-shell-jline2 and picocli-shell-jline3 combine the strength of JLine 2 and 3 with picocli.

Picocli allows you to write commands (and subcommands) with options and positional parameters using very little code, and the library will generate JLine 2 and 3 command completers for all commands.

It uses ANSI colors and styles in the usage help message, and has many other unique features like negatable options, repeatable nested argument groups, variable interpolation and more.

enter image description here

Disclaimer: I am the author and therefore biased.

Remko Popma
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1

it seems like you're trying to ask 3 different questions at once and don't know what you really want an answer to.

  • accepting user input and providing auto-complete is trivial and i highly doubt you will find a generalized library for such a task

  • parsing complex bash-like statements sounds like something cool to have and a library may exist to do that, but i don't think it would give you much headroom to create your own set of bash-like instructions. (especially considering you say it needs to be more sophisticated than anything you could do as a bash script - which is a tall order)

  • parsing simple user input as if it was a command-line input or command is also rather trivial, and if this is what you are looking for, you should look at this possible duplicate: How to parse command line arguments in Java?

i recommend restructuring your question to be more specific in exactly what you are looking for and to avoid putting emphasis on the trivial task of "auto-complete" and simply accepting the users input in a text box.

Community
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Alex Lynch
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Have you taken a look at the BeanShell? It doesn't act like a shell proper (like bash or csh) but it'll let you type java commands like an interpreter and you can use tab to autocomplete.

I've only used the 1.X versions of bean shell but they always open a window for you so it's not something you can run inside an existing shell.

Jon Lin
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  • Sounds really cool. Sounds a lot more complicated than an API that supports reading lines of user entered text, but still worth a look! – Jay Sep 26 '12 at 06:09
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I assume you mean something similar to the python interpreter. The reason there is not equivalent in Java is because Java needs to be compiled to bytecode before it can be executed.

If you are looking for something with good auto-complete capabilities. I would recommend eclipse or netbeans. They also compile your application automatically, allowing you to quickly run your code once you are done writing it.

Hope that helps.

Maybe_Factor
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  • Not quite what I was asking. Edited question for clarity. – Jay Sep 26 '12 at 06:07
  • Oh I see. I'm afraid I haven't heard of anything like that, sorry. – Maybe_Factor Sep 26 '12 at 06:21
  • And incidentally, the fact that Java is compiled doesn't really preclude having a python-like shell. Scala is compiled and runs on the JVM, and its REPL (read-eval-print-loop) works quite well. In fact, I sometimes use Scala's REPL for interactive access to Java. – jbyler Apr 29 '14 at 23:28
  • Compiling later code shouldn't change how earlier code was compiled, so it should be perfectly acceptable to compile and run each line as its entered (I assume this is how a JIT, Just In Time, compiler works). – ArtOfWarfare Jun 20 '14 at 12:00
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Bit late to the party on this one, but I'd add Crash and Cliche to the mix.

Duncan Irvine
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Apache Karaf has a command shell which can be used as a library to build a command shell for other applications. You create classes to represent commands, and use annotations to specify the options to the commands. The Karaf library provides tab completion, history and line editing, and the ability to run interactively or read in files or command line arguments to execute as a script.

I found out about it here and have used it in my own project; it works quite well. I can't compare it to any of the others as I haven't used them.

jbyler
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