Save output of external program call in textfile in java

Question

I am using Windows!

I want to call a small .exe application from my java command line which is called "saucy.exe". It needs an input file "input.saucy". Both are stored in the correct directory.

When I use the command

Process p = Runtime.getRuntime().exec("saucy input.saucy");

everything works fine and I get an output on the console.

However, when I try to write the output in a file

Process p = Runtime.getRuntime().exec("saucy input.saucy > output.saucy");

nothing happens.

I already found the advice in http://www.ensta-paristech.fr/~diam/java/online/io/javazine.html and tried to tokenize the command manually:

String[] cmd = {"saucy", "input.saucy > output.saucy"};
Process p = Runtime.getRuntime().exec(cmd);

It is still not working. Any advice? It is no option for me to write the output to a file with java code, because its too slow.

Again: I am using Windows (I stress that because I read several hints for Linux systems).

> is a shell command, but you are not using one. try String[] cmd = { "cmd", "/C", "saucy input.saucy > output.saucy" }; — Peter Lawrey
– Peter Lawrey, Commented Oct 8, 2012 at 17:58
Added it as a answer so you can accepted by ticking on the left hand side. ;) — Peter Lawrey
– Peter Lawrey, Commented Oct 9, 2012 at 10:06
If you now yould give me an advice how i can execute the program, if it is in a folder (e.g. "folder"). I tried String[] cmd = { "cmd", "/C", "folder/saucy input.saucy > output.saucy" }; and String[] cmd = { "cmd", "/C", "folder\\saucy input.saucy > output.saucy" }; which gave me the error that: application 'folder' could not been found. — user1729603
– user1729603, Commented Oct 9, 2012 at 10:09
When you give a relative path, it is relative to the current working directory. If you don't know what that will be you need to give a full path like C:\\basedirectory\\folder\\saucy — Peter Lawrey
– Peter Lawrey, Commented Oct 9, 2012 at 10:11

Peter Lawrey · Accepted Answer · 2012-10-09 10:06:28Z

1

> is a shell command, but you are not using one. try

String[] cmd = { "cmd", "/C", "saucy input.saucy > output.saucy" };

answered Oct 9, 2012 at 10:06

Peter Lawrey

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Ian Roberts · Accepted Answer · 2012-10-09 10:20:34Z

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If you are on Java 7 you can use the new ProcessBuilder.redirectOutput mechanism:

ProcessBuilder pb = new ProcessBuilder("saucy", "input.saucy");

// send standard output to a file
pb.redirectOutput(new File("output.saucy"));
// merge standard error with standard output
pb.redirectErrorStream(true);

Process p = pb.start();

answered Oct 9, 2012 at 10:20

Ian Roberts

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Pradeep Pati · Accepted Answer · 2012-10-08 18:42:50Z

0

Use the getInputStream(), getOutputStream() and getErrorStream() to retrieve the output (or send input).

http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/Process.html

answered Oct 8, 2012 at 18:42

Pradeep Pati

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