How Java calls the shell script

There are times when a feature is embedded in the Java function, which is implemented by a shell script. At this point, Java support for scripting calls is required.

Test environment

Ubuntu16.04 I3-6100,12GB

Hello World

Take a look at a basic example

    Process exec = Runtime.getRuntime().exec(new"uname" ,"-a"});    exec.waitFor();    BufferedReader reader =            new BufferedReader(new InputStreamReader(exec.getInputStream()));    System.out.println(reader.readLine());Linux jason-Inspiron-36504.4.0-121-generic #1451313:47:232018 x86_64 x86_64 x86_64 GNU/Linux

Interpreting process

The Java.lang.Process class provides a way to get input, output, wait for execution, and destroy processes.
The process class can create instances from Processbuilder.start () and runtime.exec, starting with Java1.5, Processbuilder.start () is a more recommended practice, But online tutorials are more recommended with the Runtime.exec () method.

Modifier and Type	Method	Description
abstract void	destroy ()	kills the subprocess.
abstract int	exitvalue ()	Returns The exit value for the subprocess.< /td>
abstract InputStream	geterrorstream ()	Returns the input stream Connected to the error output of the subprocess.
abstract InputStream	getinputstream ()	Returns the input stream Conne CTED to the normal output of the subprocess.
abstract OutputStream	getoutputstream ()	Returns the output stream con Nected to the normal input of the subprocess.
abstract int	waitFor ()	causes the current thread to wait, if Necessa Ry, until the process represented by this process object has terminated.

On the inheritance system, the implementation class for the process is built into the JDK, and the Linux version of the JDK comes with only one implementation class unixprocess.

Interacting with scripts

Process can not only execute processes, but also get the return results of the process.

    PrivateStringExecuteCommand(String command) {StringBuffer output =NewStringBuffer (); Process p;Try{p = Runtime.GetRuntime().exec(command);intExitCode = P.WaitFor(); System. out.println(ExitCode); BufferedReader reader =NewBufferedReader (NewInputStreamReader (p.getInputStream())); String line =""; while(line = reader.)ReadLine()) !=NULL) {output.Append(Line +"\ n"); }        }Catch(Exception e) {e.Printstacktrace(); } System. out.println(Output.toString());returnOutput.toString(); }ping www.a.Shifen.com(111.13.100.91) About( -) bytes of data. -Bytes fromlocalhost(111.13.100.91): icmp_seq=1Ttl= theTime=7.66Ms -Bytes fromlocalhost(111.13.100.91): icmp_seq=2Ttl= theTime=7.90Ms -Bytes fromlocalhost(111.13.100.91): icmp_seq=3Ttl= theTime=14.0Ms---www.a.Shifen.comPing Statistics---3Packets Transmitted,3Received0% packet loss, time 2003msrtt Min/avg/max/mdev =7.668/9.861/14.013/2.937Ms

Summarize

Java executes scripts in a way that is similar to executing scripts directly inside bash, except for some changes in the environment, and the effect of execution is basically consistent with bash.

This article was published in the public number: Cola small data (Xiaokele_data).

How Java calls the shell script