从Java调用简单的Shell脚本不起作用

Question

My Shell script named "hello"

#This is a shell script
echo "Hello Shell World!"

My Java Code,

Runtime.getRuntime().exec(new String[]{"./hello"});

My Java code is executed with no errors, but I do not see "Hello Shell World!" being printed on the terminal.

I believe my script is being executed since I do not get errors like, "hello cannot be executed, there is no such file or directory".

I am executing this on a Linux machine, Ubuntu. Thanks!

Answer 1

When running an external program from Java the output does not go to (and the input does not come from) the Java application's terminal.

The input and output streams (STDIN, STDOUT, STDERR) to the external program (your script) are directed to (from) InputStreams and OutputStreams that are accessible from the Java Process that is created when you do the exec(...)

Answer 2

You should use a reader to capture the output of the command:

Process p=Runtime.getRuntime().exec(new String[]{"./hello"});
p.waitFor();
BufferedReader reader=new BufferedReader(new InputStreamReader(p.getInputStream()));
String line=reader.readLine();
while(line!=null) {
    System.out.println(line);
    line=reader.readLine();
}