log. Sprintf

[David Renne]

I had a question that I cant seem to figure out.  I know fmt is a bad package to use if you have any concurrent workers because it uses f.Write() and is not thread safe apparently.

But I like using Sprintf because I can format strings and return as a string.  How can I implement something to use the log package in a manner that I can have a concurrently safe log function which acts like Sprintf()?

It's just so strange to me and I have always been curious of why there isnt a log.Sprintf().

[Alex Buchanan]

You mean fmt.Fprintf right? Formatting a string without writing to a io.Writer (fmt.Sprintf) must be safe for concurrent use.

The "log" package should be safe for concurrent use, and has a Printf function:

https://godoc.org/log#Logger

"""

A Logger represents an active logging object that generates lines of output to an io.Writer. Each logging operation makes a single call to the Writer's Write method. A Logger can be used simultaneously from multiple goroutines; it guarantees to serialize access to the Writer.

[Rob Pike]

fmt.Fprintf is fine for concurrent use if you use it properly. It does a single write system call to the output once the result is created. C does not guarantee that, if that's how you came to think it unsafe.

The same applies to log.Printf.

-rob

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