I wanna re-run a jar file from its own (with some additional parameters). How can I do this?
I need the solution to be OS independent.
If I deciphered the question correctly, we are talking about command line interface arguments. For this there's plenty tutorials: http://docs.oracle.com/javase/tutorial/essential/environment/cmdLineArgs.html
The code is simple, like you said yourself:
if ("-server".equalsIgnoreCase(argv)) {
// we are server
} else if ("-client".equalsIgnoreCase(argv)) {
// we are client
}
Now, depending on how you want to execute you program from the OS, there's a number of ways:
$java -jar yourjar.jar -client
Or
$java -cp yourjar.jar com.your.program.Main -client
Same for the "-server".
To run them together, either run them from separate terminal windows (or cmd prompts). Or - if in Linux - you can use ampersand:
$java -jar yourjar.jar -client &
$java -jar yourjar.jar -server &
Related
I'm trying to run a java process via Powershell in Windows XP. Here's the command:
java.exe -cp .;./common.jar -Dcontext=atest1 -Dresourcepath=. DW_Install
So, the classpath is . and .\common.jar (I think java takes the wrong slashes, right?) There are two environment variables, one "atest1" the other "." and the class to execute main on is DW_Install (in the default package).
This command works in cmd.exe, but doesn't is PS. What's going on? What is PS doing while parsing this command that CMD doesn't do (or vice versa)?
Aaron
The problem is that PS for some reason parses -Dresourcepath=. differently than cmd. What works is
java -cp '.;.\common.jar' -Dcontext=atest1 "-Dresourcepath=." DW_Install
It doesn't matter which way the slash goes, and it doesn't matter which quotes one uses (' or "). The classpath must be escaped, however, with some kind of quotes. A good test to see what's getting by the PS interpreter is to echo it. The following:
echo java -cp '.;.\common.jar' -Dcontext=atest1 -Dresourcepath=. DW_Install
yields the following output:
java
-cp
.;.\common.jar
-Dcontext=atest1
-Dresourcepath=
.
DW_Install
(Notice the resourcepath and the value of resourcepath are not on the same line.) Whereas the output to
echo java -cp '.;.\common.jar' -Dcontext=atest1 '-Dresourcepath=.' DW_Install
yields the following output:
java
-cp
.;.\common.jar
-Dcontext=etaste1
-Dresourcepath=.
DW_Install
Which is much more to our liking.
Although I wish this upon none of you, I hope that this post helps those of you that must deploy java projects on Windows machines (even though they will not run on any other platform ever).
Running external command-line programs from PowerShell is sometimes a bit problematic because there PowerShell exposes two different parsing modes that get trumped by the different syntaxes of said external programs.
In any case, running a command in Powershell requires using either the . prefix (dot-"sourcing") or the & operator.
You can workaround this by passing each parameter to the external program as separate variables, like so:
PS> $classpath = ".;./common.jar"
PS> $env = "-Dcontext=atest1 -Dresourcepath=."
PS> $class = "DW_Install"
PS> . java.exe -cp $classpath $env $class
Another example based on https://gaming.stackexchange.com/questions/24543/how-do-i-change-player-name-in-minecraft-multiplayer-in-offline-mode-in-linux
function mineCraftAs {
Param (
[parameter(mandatory=$true, HelpMessage="Minecraft character name." ,ValueFromPipeline=$true)]
[string] $name
)
if(!(test-path $env:appdata)) { $(throw "Appdata not found at $env:appdata")}
$private:minecraftPath=Join-Path $env:appdata .minecraft
if(!(test-path $minecraftPath)) { $(throw "Minecraft not found at $minecraftpath")}
$private:minebinPath=join-path $minecraftPath "bin"
if(!(test-path $minebinPath)) { $(throw "Minecraft bin not found at $minebinPath")}
$minebinPath | write-debug
gci $minebinpath | write-debug
#java -Xms512m -Xmx1024m -cp "%APPDATA%/.minecraft\bin\*" -Djava.library.path="%APPDATA%\.minecraft\bin\natives" net.minecraft.client.Minecraft '"'%1'"'
echo java -Xms512m -Xmx1024m -cp ('"'+$minebinPath+'\*"') ('-Djava.library.path="'+$minebinPath+'\natives"') net.minecraft.client.Minecraft ($name)
$minecraftJob=& 'C:\Program Files (x86)\Java\jre6\bin\java.exe' -Xms512m -Xmx1024m -cp ('"'+$minebinPath+'\*"') ('-Djava.library.path="'+$minebinPath+'\natives"') net.minecraft.client.Minecraft ($name)
}
minecraftas newbie
The following should work:
java.exe -cp '.;./common.jar' -Dcontext=atest1 -Dresourcepath=. DW_Install
I guess that PowerShell interprets the ; in the classpath as command delimiter, thereby trying to run java -cp . and ./common.jar -D....
start-process -nnw java "-cp .;./common.jar -Dcontext=atest1 -Dresourcepath=. DW_Install"
I have a program in java which takes 0'th aargument as file location like
File f = new File(args[0]);
so when i execute it using a windows batch(.bat) file it works correctly .
but when i execute the same using a linux shell file(.sh) in linux i get ArrayIndexOutOfBoundsException.
WINDOWS BATCH FILE :
#echo off
for /f %%i in ("%0") do set scriptpath=%%~dpi
set cp=%scriptpath%/../lib/*.jar;
java -classpath %cp% com.synchronizer.main.MYSynchronizer %scriptpath% "%1" "%2"
LINUX SH FILE:
export JAVA_HOME=/usr/local/java
PATH=/usr/local/java/bin:${PATH}
THE_CLASSPATH=
for i in `ls ../lib/*.jar`
do
THE_CLASSPATH=${THE_CLASSPATH}:${i}
done
java -cp ".:${THE_CLASSPATH}" \
com.synchronizer.main.MYSynchronizer
please help!
It looks like a problem in script (no arguments are passed to the Java program).
You can consider to debug the script like this: debugging scripts
Hope this helps
Your shell script is not passing any parameters:
java -cp ".:${THE_CLASSPATH}" com.synchronizer.main.MYSynchronizer
Try:
java -cp ".:${THE_CLASSPATH}" com.synchronizer.main.MYSynchronizer "$1" "$2"
As stated above, your Linux shell script is not sending any arguments to the Java program that you are trying to start.
And, adding to that, you are not showing us how you run the Linux shell script. If no argument is given on the command line when you start the shell script, no arguments can be passed to your Java application from the shell script.
If you want to see the actual command that is going to be run by your shell script, you can always put "echo" in front of a line and see what all variables are expanded to. This is a simple way to debug shell scripts.
How to execute a java file by shell script?
If it's packed up as a jar:
java -jar jarfile.jar
If it is a class file:
java myClassFile
If it is a jar file:
java -jar myJarFile.jar
See:
Tutorial: http://javabeanz.wordpress.com/2009/01/29/running-an-executable-jar-from-command-line/
Official documentation: http://download.oracle.com/javase/1.4.2/docs/tooldocs/windows/java.html
java com.foo.Boo
All the answers only show the terminal commands to compile and run .java files but not the shell script to do so.
Below is the shell script. Let's call it compileRunJava.sh
javac $1
java ${1%.java}
You may need to giv terminal the permission to run your script -
$ sudo chmod 754 compileRunJava.sh
Let's say your .java file is Hello.java. To run the script, cd to the directory where you have Hello.java. Run the below command -
$ /path/to/shell/script/directory/compileRunJava.sh Hello.java
There's a nifty little trick after if you're using java 11 or more. To execute a single class you can do the following.
PS: This is for unix based systems, IDK about windows.
Step 1: Create A File by executing the command
$ touch hello
Step 2: Add code to the file by using vi or any other text editor. My code looks like this.
#!/usr/bin/java --source <GET_YOUR_JAVA_VERSION>
public class Main{
public static void main(String... args){
System.out.println("Hello");
}
}
Notice the shebang line. That is required.
Step 3: Make that file executable by executing the following command.
$ chmod +x hello
Step 4: Execute the file
$ ./hello
Hello
This is a great thing that is introduced after java 11. You can read about it more over here.
I have a bash script that calls a java class method. The method returns a string to the linux console when run independently. how can I assign the value from the java method to a variable in a bash script?
running the script:
java -cp /opt/my_dir/class.method [parameter]
output: my_string
if added in a bash script:
read parameter
java -cp /opt/my_dir/class.method [parameter] | read the_output
echo $the_output
the above doesnt work, I also tried unsuccessfully:
the_output=java -cp /opt/my_dir/class.method [parameter]
the_output=`java -cp /opt/my_dir/class.method [parameter]`
java -cp /opt/my_dir/class.method [parameter] 2>&1
How can i get the output stored into the_output variable?
thanks.
In Bash:
$ the_output="$(java -cp /opt/my_dir/class.method [parameter])"
See: http://www.gnu.org/software/bash/manual/bashref.html#Command-Substitution
EDIT:
Actually, looking at your command-line, I'm surprised that it works. I haven't seen a Java program called like that before. Usuallly you can only run a main() method from a java command. How does yours work?
EDIT:
You say that you are still getting output going to the console when you do this. You may need to capture stderr too:
$ the_output="$(java -cp /opt/my_dir/class.method [parameter] 2>&1 )"
2> means redirect stderr (file descriptor 2). &1 means to the same place as stdout (file descriptor 1) is going.
Use command substitution by wrapping your command in backquotes.
Try bashj (a bash mutant with java support) https://sourceforge.net/projects/bashj/.
for instance:
#!/usr/bin/bashj
X= Math.cos(0.5)
Y= Math.hypot(3.0,4.0)
Z= System.getProperty("java.runtime.version")
You can also put your own methods in a jar loaded by bashj, or include some java source code within the bashj script:
#!/usr/bin/bashj
#!java
public static int factorial(int n)
{if (n<=0) return(0);
if (n==1) return(1);
return(n*factorial(n-1));}
##bash
echo j.factorial(10)
This is much faster than any solution involving the creation of a new JVM process.
-java -classpath<> <classname> in the ".bat" file to launch java test from cmd windows
how to do that using perl to launch java test from linux ?
Don't use perl. For such a simple job, a simple shell script will do:
#!/bin/sh
/path/to/java -classpath foo.jar:bar.jar:. classname
Make the file executable with chmod +x filename and execute it with ./filename
A similar approach using the -jar option is possible. Additionally, you can forward any command line parameters using the special parameter #.
#!/bin/sh
/path/to/java -jar foo.jar "${#}"