Is there a way to read data from the command prompt? I have a java program that relies on 4 input variables from an outside source. These variables are returned to the command prompt after I run a javascript program but i need a way to pass these variables from the command prompt into my java program, any help would be greatly appreciated!
While executing java program pass the parameters and all the parameters should be separated by space.
java programName parameter1 parameter2 parameter3 parameter4
This parameters would be available in your main method argument
public static void main(String[] args){
//This args array would be containing all four values, i.e. its length would be 4 and you easily iterate values.
for(int i=0; i<args.length; i++){
System.out.println("Argument " + i + " is " + args[i]);
}
Follow the link:
Command-Line Arguments - The Java™ Tutorials : https://docs.oracle.com/javase/tutorial/essential/environment/cmdLineArgs.html
shared by #BackSlash.
It has all the content which would help you to clear all your doubts.
The content from the link is quoted below:
Displaying Command-Line Arguments passed by user from command-line to a Java program
The following example displays each of its command-line arguments on a
line by itself:
public class DisplayCommandLineParameters {
public static void main (String[] args) {
for (String s: args) {
System.out.println(s);
}
}
}
To compile the program: From the Command Prompt, navigate to the directory containing your .java file, say C:\test, by typing the cd
command below.
C:\Users\username>cd c:\test
C:\test>
Assuming the file, say DisplayCommandLineParameters.java, is in the
current working directory, type the javac command below to compile it.
C:\test>javac DisplayCommandLineParameters.java
C:\test>
If everything went well, you should see no error messages.
To run the program: The following example shows how a user might run the class.
C:\test>java DisplayCommandLineParameters Hello Java World
Output:
Hello
Java
World
Note that the application displays each word — Hello, Java and World —
on a line by itself. This is because the space character separates
command-line arguments.
To have Hello, Java and World interpreted as a single argument, the
user would join them by enclosing them within quotation marks.
C:\test>java DisplayCommandLineParameters "Hello Java World"
Output: Hello Java World
Related
I have a java class which is to be made into a tool so that I can give the input to the class as parameters and then produce the output in the command line, I have written the code in IntelliJ and want the code to be portable so that it can be used instantly by the click of a button. I have little experience in creating a bat file or python script.
package ase.ATool;
import java.io.*;
import java.util.*;
import java.util.regex.*;
public class AnaliT {
public static void main(String[] args) {
File file = null;
File dir = new File(args[0]);
File[] directoryListing = dir.listFiles();
StringBuffer componentString = new StringBuffer(100);
if (directoryListing != null) {
for (File child : directoryListing) {
float complexity = 0, noOfMethods = 0;
System.out.println(child.getPath() + " ");
String currentLine;
BufferedReader bufferedReader = null;
try {
bufferedReader = new BufferedReader(new FileReader(child.getPath()));
System.out.println(bufferedReader);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
I want to convert the above code in to a tool so i can invoke this main function from the command line, batch file or python file.
You could compile and run the java file from python by checking out the subprocess module:
https://docs.python.org/3/library/subprocess.html
You can also run java code using the system module: running a java file in python using os.system()
If you want to invoke Java code from python, take a look here:
Calling Java from Python
Here it is recommended you use Py4J.
Here you can find an example of running a Java Class from a .bat file: How to run java application by .bat file
As mentioned in a comment you can also compile the file with java using java target.java and then run it with java target in the same directory
I hope by showing you some of these resources you can guide yourself towards more specific help.
I've created the following C# Console Application (.NET Core 3.1) with Visual Studio:
using System;
namespace ConsoleApp2
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
//Check if args contains anything
if (args.Length > 0)
{
Console.WriteLine("args = " + args[0]);
} else
{
Console.WriteLine("args is empty");
}
//Prevent the application from closing itself without user input
string waiter = Console.ReadLine();
}
}
}
I am able to execute the application succesfully with one argument via cmd.exe:
CMD Input and Output
Now I'd like to run this program with one argument via Python. I've read How to execute a program or call a system command? and tried to implement it. However, it seems that the application is not being run properly.
The python code I am using via Jupyter notebook:
import subprocess
path = "C:/Users/duykh/source/repos/ConsoleApp2/ConsoleApp2/bin/Release/netcoreapp3.1/ConsoleApp2.exe"
subprocess.Popen(path) //#Also tried with .call and .run
//#subprocess.Popen([path, "argumentexample"]) doesn't work either
Output:
<subprocess.Popen at 0x2bcaeba49a0>
My question would be:
Why is it not being run (properly) and how do I properly run this application with one argument?
I've answered my own question. In a nutshell: I am pretty stupid.
Jupyter Notebook was running in the background and the application was being run there. That's why it didn't open a new prompt.
subprocess.Popen([path, "argument example"]) seems to work well for running a console application with an argument as input.
I want to call python script from node.js
Here is my script : my.py
def printme( str ):
# print str;
return str;
printme("I'm first call to user defined function!");
printme("Again second call to the same function");
My node script : testpy.js
var PythonShell = require('python-shell');
var pyshell = new PythonShell('my.py');
pyshell.on('message', function(message) {
console.log(message);
});
but getting error
events.js:85
throw er; // Unhandled 'error' event
Error: spawn python ENOENT
at exports._errnoException (util.js:746:11)
at Process.ChildProcess._handle.onexit (child_process.js:1046:32)
at child_process.js:1137:20
at process._tickCallback (node.js:355:11)
at Function.Module.runMain (module.js:503:11)
at startup (node.js:129:16)
at node.js:814:3
P.S I have install Python shell
Also if I want to execute individual function from node.js to python script. can I do that ?Help
You can simply write the 'my.py' file like this-
def printme(str):
return str;
print(printme("I'm first call to user defined function!"));
Check if the path given is correct and check for indentation errors.
Your print statement (my.py line 2) is commented out so nothing will be output and the message event will therefore never fire. Uncomment your print statement, the Node PythonShell object will redirect the stdout (which print writes to) and fire a message event with the output.
As for your error, it looks like the python script isn't being found in the current directory. See https://docs.python.org/2/library/errno.html for error codes and what they mean. Make sure your script is in the right directory or set your python shell to the correct directory using os.chdir.
I think that you need to set up the python script to take in standard input like this
import sys
for v in sys.argv[1:]:
print v
Also when setting up the code the way you have it you need to do a PyhtonShell.send('message'), but I would need to see more of your code because I don't see how you are sending data to the python shell through Node.js.
You can simply import Npm Pythonshell using let keyword instead of const Keyword.
let {PythonShell} = require('python-shell')
this works for me
When I'm working on a bash script and need to write a particularly complex logic I usually fall back on using python, like this:
#!/bin/bash
function foo() {
python << END
if 1:
print "hello"
END
}
foo
How can I do the same thing from within a Makefile?
You may write a bash script containing your functions, say myscript.sh:
#!/bin/bash
foo() {
python << END
if 1:
print "hello $1"
END
}
Now here is a Makefile:
SHELL = /bin/bash
mytarget ::
#source myscript.sh ;\
foo world
Finally type in your terminal:
$ make mytarget
hello world
Some explanations on the Makefile: defining SHELL let make know which shell to run. The :: stands for phony target (and a little more); you can replace it with : for an actual target.
The key point is to run source and call the function in the same shell, that is, in the same line (since make run a different shell for each line); this is achieved by ;\ at the end of each line.
I am really fond of python's capability to do things like this:
if __name__ == '__main__':
#setup testing code here
#or setup a call a function with parameters and human format the output
#etc...
This is nice because I can treat a Python script file as something that can be called from the command line but it remains available for me to import its functions and classes into a separate python script file easily without triggering the default "run from the command line behavior".
Does Powershell have a similar facility that I could exploit? And if it doesn't how should I be organizing my library of function files so that i can easily execute some of them while I am developing them?
$MyInvocation.Invocation has information about how the script was started.
If ($MyInvocation.InvocationName -eq '&') {
"Called using operator: '$($MyInvocation.InvocationName)'"
} ElseIf ($MyInvocation.InvocationName -eq '.') {
"Dot sourced: '$($MyInvocation.InvocationName)'"
} ElseIf ((Resolve-Path -Path $MyInvocation.InvocationName).ProviderPath -eq $MyInvocation.MyCommand.Path) {
"Called using path: '$($MyInvocation.InvocationName)'"
}
$MyInvocation has lots of information about the current context, and those of callers. Maybe this could be used to detect if a script is being dot-sourced (i.e. imported) or executed as a script.
A script can act like a function: use param as first non-common/whitespace in the file to defined parameters. It is not clear (one would need to try different combinations) what happens if you dot-source a script that starts param...
Modules can directly execute code as well as export functions, variables, ... and can take parameters. Maybe $MyInvocation in a module would allow the two cases to be detected.
EDIT: Additional:
$MyInvocation.Line contains the command line used to execute the current script or function. Its Line property has the scrip text used for the execution, when dot-sourcing this will start with "." but not if run as a script (obviously a case to use a regex match to allow for variable whitespace around the period).
In a script run as a function
As of now I see 2 options that work
if ($MyInvocation.InvocationName -ne '.') {#do main stuff}
and
if ($MyInvocation.CommandOrigin -eq 'Runspace') {#do main stuff}
Disclaimer: This is only tested on Powershell Core on Linux. It may not work the same for Windows. If anyone tries it on Windows I would appreciate if you could verify in the comments.
function IsMain() {
(Get-Variable MyInvocation -Scope Local).Value.PSCommandPath -Eq (Get-Variable MyInvocation -Scope Global).Value.InvocationName
}
Demonstrated with a gist