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This article mainly introduces "how to call java.lang.Runtime.exec correctly". In daily operation, I believe many people have doubts about how to correctly call java.lang.Runtime.exec. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts about "how to call java.lang.Runtime.exec correctly". Next, please follow the editor to study!

Call the correct posture of java.lang.Runtime.exec

I encountered a problem when I wrote a program that used to compile today.

In the call

Runtime.exec ("javac HelloWorld.java")

It works perfectly, that is, there is a generated .class.

And here it is.

Runtime.exec ("java HelloWorld > > output.txt")

But there is no way to redirect the output, not even the output.txt file can be generated.

It is not allowed to test "echo hello > > 1.txt". It is a headache, so I look through the materials and find out.

A misunderstanding is that in exec (str), str cannot be completely regarded as the command of command line execution. In particular, redirection cannot be included in str'

'and pipe characters'|'.

So, what are we going to do with such instructions? Let's move on to the following:

Two methods

One is to write instructions into a script and invoke the script in runtime.exec (). This approach avoids the use of exec (), and is also a way of thinking.

Another way is to call the overloaded method of exec (): let's focus on this method:

Let's take a look at the official doc [> link output.txt] first.

The second overload of exec is used, that is, the input parameter is String []:

Process p = Runtime.getRuntime () .exec (new String [] {"/ bin/sh", "- c", "javap-l xxx > output.txt"}); at this point, the study on "how to invoke java.lang.Runtime.exec correctly" is over, hoping to solve everyone's doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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