How Can I Print Debugging Messages to Standard Error (stderr) in Go?

Printing Messages to Standard Error (stderr) in Go

Maintaining separate logs for debugging and testing can be challenging, especially when existing logs are voluminous. Writing to standard error (stderr) provides a convenient way to isolate debugging logs while suppressing other output.

Methods for Printing to stderr

Go offers several methods to print messages to stderr:

1. Creating a New Logger

Instantiate a custom logger using log.New():

<code class="go">l := log.New(os.Stderr, "", 1)
l.Println("log message")</code>

2. Using fmt.Fprintf

Invoke fmt.Fprintf to write directly to stderr:

<code class="go">fmt.Fprintf(os.Stderr, "log message: %s", str)</code>

3. Writing to os.Stderr

Directly write to stderr using os.Stderr.WriteString():

<code class="go">os.Stderr.WriteString("log message")</code>

Deflecting Standard Output to /dev/null

To suppress the output from other logging mechanisms, deflect standard output to /dev/null using the following command:

<code class="sh">go run main.go 1>&/dev/null</code>

By employing these methods, you can efficiently isolate and review your custom logs for debugging and testing purposes.

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