Java-从程序获取输出…命令行参数？

Question

I am writing a Java program and would be calling this in a DOS batch script....(it is a Swing based GUI application) I wish to get output from the Java program in the calling DOS script. I am planning to get this information out through the use of command line arguments - like

(in the DOS script)

java myProg var

if (%var% == "loggedin") {

}

var is supposed to be populated with the output from myProg. The Java program myProg is supposed to set the value args[0] (in var) and I am assuming this will be remembered when control comes back to the DOS script. Is this possible? If not how can I achieve my use-case? What options do I have? How can I pass a flag (as "loggedin") from myProg to the calling DOS batch script?

Answer 1

Edit: try to use dos command "pipe":

Command1 | Command2

the output (eg: System.out.println()) of Command1 will be the input argument of Command2 The Command1 is the command which run the java app The Command2 is the batch file which process args as %1, %2

Answer 2

Command line arguments cannot be modified; they are literals. The only thing you can do is have text output to stdout or stderr (as yelliver suggested), set an environment variable, write to a log file of some kind, or return an exit code.

Answer 3

The way to "populate var with the output from myProg" is this (in the DOS script):

for /F "delims=" %%a in ('java myProg') do set "var=%%a"

Note that the Java program must "output" the value you want to assign to var, that is, it must show that value in the screen (via Stdout).