Why Are My Go Logs Not Writing to File?

Writing Logs to a File in Go

When attempting to write logs to a file using the standard Go logging package, users may encounter issues where the log file is created but remains empty. To resolve this, it's essential to understand the correct approach to writing logs to a file.

In the provided code, you've attempted multiple approaches, including:

• Setting os.Stderr and the file as io.MultiWriter for log output.
• Setting the file as io.Writer for log output.
• Directly setting the file as the output for logging.

However, all of these methods have failed because os.Open("logfile") opens the file for reading only, making it unsuitable for writing logs.

The correct approach is to use os.OpenFile("testlogfile", os.O_RDWR | os.O_CREATE | os.O_APPEND, 0666). This opens the file for both reading and writing, allowing logs to be appended to the file.

By adding this line and setting the log output to the file, you can successfully write logs to a file in Go:

f, err := os.OpenFile("testlogfile", os.O_RDWR | os.O_CREATE | os.O_APPEND, 0666)
if err != nil {
    log.Fatalf("error opening file: %v", err)
}
defer f.Close()

log.SetOutput(f)
log.Println("This is a test log entry")

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