Processing 1.0 - Processing Discourse - appending to a text file

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Index › Programming Questions & Help › Syntax Questions › appending to a text file

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appending to a text file (Read 602 times)

dcs

appending to a text file
Jun 5^th, 2009, 7:22am

I wish to be able to open a text file for logging and append records to the end of the file. I cant get the syntax right. In the eg below I use createWriter, however as it name implies it overwrites the previous version.

------------------
static String aFile = "test.txt";
PrintWriter output;

void setup() {
output = createWriter(aFile);
}

void draw() {

output.println("blahblah");
}

void keyPressed() {

output.flush();
output.close();
exit();
}

PhiLho

Re: appending to a text file
Reply #1 - Jun 5^th, 2009, 8:06am

Looks like the case isn't handled.
Two solutions:
- Read the whole file, re-create it with new stuff. Quite impractical...
- Use the following:

Code:

PrintWriter appendWriter(String filename) {
    try {
	File file = saveFile(filename);
	OutputStream output = new FileOutputStream(file, true);
	return createWriter(output);
    } catch (Exception e) {
	e.printStackTrace();
	throw new RuntimeException("Couldn't create a writer for " +
		filename);
    }
}

Warning: not tested!
That's a variant of the code of createWriter as found in PApplet.java.
The key is the true parameter given to the FileOutputStream constructor, telling it to append.

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