Go:
Writing to standard error

How To:

In Go, the os package provides the Stderr value, representing the standard error file. You can use it with fmt.Fprint, fmt.Fprintf, or fmt.Fprintln functions to write to stderr. Here’s a straightforward example:

package main

import (
    "fmt"
    "os"
)

func main() {
    // Writing a simple string to stderr
    _, err := fmt.Fprintln(os.Stderr, "This is an error message!")
    if err != nil {
        panic(err)
    }

    // Formatted error message with Fprintf
    errCount := 4
    _, err = fmt.Fprintf(os.Stderr, "Process completed with %d errors.\n", errCount)
    if err != nil {
        panic(err)
    }
}

Sample output (to stderr):

This is an error message!
Process completed with 4 errors.

Remember, these messages will not appear in the regular output (stdout) but in the error stream, which can be redirected separately in most operating systems.

Deep Dive

The concept of standard error is deeply rooted in Unix philosophy, which clearly distinguishes between normal output and error messages for more efficient data processing and handling. In Go, this convention is embraced through the os package, which provides direct access to the stdin, stdout, and stderr file descriptors.

While writing directly to os.Stderr is suitable for many applications, Go also provides more sophisticated logging packages like log, which offers additional features such as timestamping and more flexible output configurations (e.g., writing to files). Using the log package, especially for larger applications or where more comprehensive logging features are needed, can be a better alternative. It’s also worth noting that Go’s approach to error handling, which encourages returning errors from functions, complements the practice of writing error messages to stderr, allowing for more granular control of error management and reporting.

In essence, while writing to stderr is a fundamental task in many programming languages, Go’s standard library and design principles offer both straightforward and advanced paths to managing error output, aligning with broader industry practices while also catering to Go’s specific design ethos.