Project bashj : a bash mutant with java support

What ?

The bashj project is hosted on sourceForge.

bashj is an extended bash allowing to use java libraries, functions and code from bash scripts.

version 0.982 (june 2018) this is still a beta release...

Why ?

Java and bash are often partners in software projects.

Personnally 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 incapacity 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 quickly and directly call java methods without creating new OS processes.

How ?

A bashj server (a java daemon process)  communicates with bash scripts (considered as clients).

A dedicated function (jsb()) is internally defined. It is used from bash script clients to request server actions.

The communication uses two named pipes.

All this may be also be seen as a bash preprocessor.

Limitations

• bash scripts only (not usable interactively)
• Linux only
• java 9+
• requires javac (JDK installed)
• only public static methods may be called 
• methods with primitive types (including String) as parameters and return value
• no varargs

Installation

Follow carefully these steps:

1. create a directory  :  sudo mkdir -m=777  /var/lib/bashj/
2. download from  sourceForge the bashjInstall.jar installation file and move it in this directory
3. go to the installation directory : cd /var/lib/bashj/
4. run in bash : jar xvf bashjInstall.jar
5. chmod +x ./bashjInstall
6. run in bash : sudo ./bashjInstall

For the uninstallation:

1. run bashjUninstall 

Check, try and test

Various bashj scripts examples are in /var/lib/bashj/example/.

cd /var/lib/bashj/example/    # going to the example directory

ls                            # view list of examples

cat javaLang                  # having a look at the code

./javaLang                    # running the code

The same may be realized for all example scripts.

It is suggested to try, copy, adapt these examples scripts.

bashj syntax rules and java calls

The bashj interpreter only works for scripts. It may not be used for an interactive session.

A bashj file is similar to a standard bash file. Just replace the shebang : #!/usr/bin/bashj instead of #!/bin/bash.

Several families of java methods & fields may be called

• Those defined in the beginning of the running bash script itself, between a line containing #@java and a line containing #@bash. Java methods are defined there without package name and without class name. The implicit class name is "j". So a function public static int factorial(int n) may be called in the script body as j.factorial(int).
• Those present in the standard java packages java.lang.System  and java.lang.Math  (possibly more later if requested). 
• The control methods provided by the bashj server:

server.info()

server.classes()

server.classes(String grep)

server.methods()

server.methods(String grep)

server.fields()

server.fields(String grep)

• Those provided as utilities as part of bashj. They are accessible with a class name "u", for instance u.toUpperCase(String) or yellow(String). The list is available using server.methods("bashj.u").
• Those present in jars put by the user in the subdirectory jarlib.

Methods may be called with various equivalent syntax. The following lines (in a bashj script) provide the same result :

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 most readable and recommended.

The call produces a bash varaibale wich my be used in the usual ways:

echo Math.hypot(3.0,4.0)

HYPOT = Math.hypot(3.0,4.0)

Void java methods should be called using this syntax:

: server.info()

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 bashj interpreter.

They should be called as indicated before.

Improvements

• ? Handle varargs argument.
• ? Create a installable package for debian distribs.
• ? Organize the bashj server as a Linux service

Annexes

Support

Please contact fil@gonze.org for support, remarks, suggestions,...

Installed Files

The files are installed under /var/lib/bashj/, and include:

• bashjInstall.jar (a jar containing all bashj required files)
• bashjInstall (an installation script) & bashUninstall
• bashjServer.jar (a jar containing the compiled java class bashj.server.class)
• bashj (a script, the command interpreter) (a link is created in /usr/bin)
• README a readme file (a short intro to 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  to bashj
• example/ a subdirectory with various example scripts (executable files)

Script examples

#!/usr/bin/bashj

#@java

public static int factorial(int n) 
{if (n<=0) return(0);
 if (n==1) return(1);
 return(n*factorial(n-1));}

#@bash

echo j.factorial(10)
#!/usr/bin/bashj

#@java
public static void test(int k)
{u.p("Hello world");
 u.p("This code is executed in a JVM "+System.getProperty("java.version"));
 u.p("But it is processed through bashj and finally bash");}
#@bash
 : j.test(0)

#!/usr/bin/bashj

echo Math.cos(0.5)
echo Math.hypot(3.0,4.0)
echo System.getProperty("java.runtime.version")
#!/usr/bin/bashj

#@java

public static String ax2_bx_c(double a,double b,double c)
{final double r=b*b-4*a*c;
 if (r<0.0) return("NoRoot");
 if (r==0.0) return(""+(-b/(a+a)));
 final double sq=Math.sqrt(r);
 return(""+(-b-sq)/(a+a)+" "+(-b+sq)/(a+a));}

#@bash

echo "... Delivers the roots of a quadratic equation"

A=1.0
B=-5.0
C=6.0
echo "... Solving $A X^2 + $B X + $C"

echo "... Roots are " j.ax2_bx_c($A,$B,$C) 
#!/usr/bin/bashj

echo "bashj server utilities"
echo
 : server.classes()
echo
 : server.methods("bashj.u.")
echo
 : server.fields("ersion")
echo
 : server.info()

#!/usr/bin/bashj

echo "bashj string utilities\n"

WORD=Bonjour
echo length of $WORD is u.strlen($WORD)

LETTER=u
echo index of $LETTER in $WORD is u.indexOf($WORD,$LETTER)

echo Uppercase u.toUpperCase($WORD)
echo Lowercase u.toLowerCase($WORD)
#!/usr/bin/bashj

echo Tkol.colored(200,100,100,Hi)
echo qis.kb3(9999)