Project bashj : a bash mutant with java support
What ?
The bashJ & java Shell Bridge project is hosted on sourceForge.
bashJ is an extended bash allowing to use java libraries and java code in bash scripts.
Java Shell Bridge is the underlying technology used by bashJ. It is mainly a server executing java code for the benefit of a bash session (interactive or scripted).
[ In june 2018 - this is still a beta release ]
Why ?
Java and bash are often partners in software projects.
Personnaly I used both of them widely. Being rather lazy, I tried to minimize the number of necessary techonologies in my projects. These two covered 99% of my needs together. Java is perfect to translate concepts into software. But bash is necessary for various OS level tasks, like process control, deployment ... But I was frequently disappointed by the incapacty to reuse java results and expertise from scripts (this was only possible with java process launching, and main() entry points). So I decided to set up the tool described here...
Their possible interactions are numerous but limited in terms of integration.
With this project, any script is given the capacity to quicly and directly call java methods without creating new OS processes.
How ?
The JSBServer communicates with bash specialized function using double named pipes.
Limitations &
- bash only
- Linux only
- java 9+
- public static methods only
- methods with primitive types (including String) as parameters and return value
- no varargs
Installation
Follow carefully these steps:
- create a directory /var/lib/jsbridge/
- download from sourceForge the jsbInstall.jar installation file and put it in this directory
- go to the installation directory : cd /var/lib/jsbridge/
- run in bash :jar xvf jsbInstall.jar
- run in bash : sudo ./jsbInstall
Check try test
After the installation run these commands in a bash terminal. Their output should be self explanatory...
Examples
It is suggested to try, copy, adapt some examples scripts present in the example subdiretory
bashJ syntax rules and java calls
The bashJ is only available in scripts. It may not be used for an interactive session.
A bashJ file is similar to a standard bash file. Just replace the shebang : #!/bin/bashJ instead of #!/bin/bash.
Three kind of java methods & fields may be called
- Those defined in the beginning of the bash file, between a line containing #@javaStartand a line containing #@javaEnd. Java methods are define there without package name and without class name. The implicit method name is "j". So a function public static int factorial(int n) may be called as j.factorial().
- Those present in the standard java packagesjava.lang.System java.lang.String and java.lang.Math .
- Those present in jars put by the user in the subdirectory jarlib.
Methods max be called with various equivalent syntax. The following lines (in a bash script) are equivalent:
- echo Math.hypot(3.0,4.0)
- echo java.lang.Math.hypot(3.0,4.0)
- echo $(jsb Math.hypot 3.0 4.0)
The first one is the preferred one.
Configuration
No configuration is necessary.
However it is possible for the user to put various jar files under the jarlib directory.
All public static methods and all public static fields defined in these classes will be available in the bridge.
They should be called as indicated before.
Support
Please contact fil for support, remarks, suggestions,...
Annex : installed Files
The files are installed under /var/lib/jsbridge/, and include:
- JSBServer.jar (a jar containing a compiled java class)
- jsbInit (a set of bash functions) (a link is created in /usr/bin)
- bashJ (a script, the command interpreter) (a link is created in /usr/bin)
- README a readme file (a short version of this page)
- pipe/a subdirectory used for named pipes
- classes/ a subdirectory with transient compiled java classes
- jarlib/ a subdirectory with the jars choosen by the user to make the involved classes available
- example/ a subdirectory with various example scripts