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This article mainly introduces Java how to execute cmd commands and what matters to pay attention to the relevant knowledge, the content is detailed and easy to understand, the operation is simple and fast, with a certain reference value, I believe that after reading this Java how to implement cmd commands and what matters to pay attention to the article will have a harvest, let's take a look at it.

Usually, Java uses Runtime.getRuntime.exec (command) to execute Windows or Linux commands.

Eg1: execute the command public static void execCommand () {try {Runtime runtime = Runtime.getRuntime (); / / Open the task manager. After calling the exec method, return the Process process object Process process = runtime.exec ("cmd.exe / c taskmgr"); / / wait for the execution of the process object to complete and return the "exit value". 0 is normal, the other is the exception int exitValue = process.waitFor () System.out.println ("exitValue:" + exitValue); / / destroy the process object process.destroy ();} catch (IOException | InterruptedException e) {e.printStackTrace ();}} eg2: execute the command and get the normal and error output public static void execCommandAndGetOutput () {try {Runtime runtime = Runtime.getRuntime () Process process = runtime.exec ("cmd.exe / c ipconfig"); / / output result, must be written before waitFor String outStr = getStreamStr (process.getInputStream ()); / / error result, must be written before waitFor String errStr = getStreamStr (process.getErrorStream ()); int exitValue = process.waitFor () / / the exit value 0 is normal, and the others are exception System.out.println ("exitValue:" + exitValue); System.out.println ("outStr:" + outStr); System.out.println ("errStr:" + errStr); process.destroy ();} catch (IOException | InterruptedException e) {e.printStackTrace () } public static String getStreamStr (InputStream is) throws IOException {BufferedReader br = new BufferedReader (new InputStreamReader (is, "GBK")); StringBuilder sb = new StringBuilder (); String line; while ((line = br.readLine ())! = null) {sb.append (line); sb.append ("\ n");} br.close (); return sb.toString ();}

By manipulating the data flow, the process object can input parameters to the executed command, obtain the output result of the command, and obtain the error result.

GetInputStream () gets the output data of the process process getOutputStream () gets the input data of the process process getErrorStream () gets the error data of the process process it is worth noting that:

Why does getInputStream () get the output data? Why does getOutputStream () get input data? This is because input and output are _ _ for the program that currently calls process, that is

To get the output of the command, the result of the executed command is inputted into our own program, so use getInputStream ()

To input data into other programs, our program needs to output, so use getOutputStream () at this time.

Attach java to call cmd command to realize various operations

In java programming, sometimes we only need to use our own program or call a third-party plug-in to complete some work, but because of personal whim, although the cmd command is not very bad, can we directly write the command into the java program and control the inside of the computer in our own program? For example, it may be more convenient to understand, because I have to download resource files at night, but I also want to sleep, so leaving the computer on not only consumes the computer, but also may affect the quality of my sleep. Although I know the cmd shutdown command, I can write an executable fragment of java, and then use this to perform a regular shutdown operation on the computer. In this way, if I need to set the shutdown, I can call my own program directly. Although there are special gadgets on the market, what I write will always bring a little Aojiao. I hope you can study the specific operation by yourself, but you should know that the cmd command can do a lot of things, so how to use the cmd command in java is very interesting:

Public static void main (String [] args) {/ * get the cmd command * / try {Process pro = Runtime.getRuntime () .exec ("cmd / c calc"); / / add the command to be carried out. Calc in "cmd / c calc" means to open the calculator. How to set the shutdown, please find the cmd command BufferedReader br = new BufferedReader (new InputStreamReader (pro. GetInputStream (). / / although the cmd command can be output directly, the data can be buffered by IO streaming technology. String msg = null; while ((msg = br.readLine ())! = null) {System.out.println (msg) }} catch (IOException exception) {} / * cmd / c dir is to close the command window after executing the dir command cmd / k dir is not to close the command window after executing the dir command cmd / c start dir will open a new window and execute the dir command, the original window will close cmd / k start dir will open a new window and execute the dir command, the original window will not close cmd /? View help information * /}

I would like to remind you here that the integration of cmd commands into the program is sometimes of some practical use, such as my project requires that once the user has done something, the computer needs to be turned off, then this is a simple use.

This is the end of the article on "how Java executes cmd commands and what matters you should pay attention to". Thank you for reading! I believe you all have a certain understanding of "how Java executes cmd commands and what matters you should pay attention to". If you want to learn more, you are welcome to follow the industry information channel.

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