NSLog() to both console and file

objective-c nslog
Miroslav Kovac picture Miroslav Kovac · Mar 8, 2012 · Viewed 12.9k times · Source

I would like to redirect NSog() to file, but still to see the output in console. I am aware that stderr can be redirected to file using:

freopen("file.log", "a+", stderr);

but after redirecting it to file, the log is no more shown in the console output.

I could build a custom wrapper around NSLog() but I would not get logged crash logs that are written to stderr in the moment of app crash.

I was also experimenting with dup() and other methods for duplicating file descriptors, but the output was ether in file or in console, never in both.

Similar questions was asked here: Write stderr on iPhone to both file and console but without accepted answer, or with suggestion to use a NSLog() wrapper.

Has anyone an idea on how to manage this work? Thanx in advance.

UPDATE: The most important part of redirecting is to have system error logs (stderr) written to both console and file.

Answer

Sailesh picture Sailesh · Mar 8, 2012

The way we have implemented is:

if (!isatty(STDERR_FILENO)) {
    // Redirection code
}

This is based on general assumption that if a console is attached, you do not need to store those logs in the file since you are already debugging. So whenever the console is attached, logs will be printed there, otherwise saved to a file.

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