gistfile1.md

Explain this code. User is in go mode.

func main() {
	flag.Usage = func() {
		fmt.Printf("%s <file>\n\nprints file to standard out\n", os.Args[0])
	}
	flag.Parse()

	if flag.NArg() != 1 {
		log.Fatalf("wanted 1 arg, got %#v", os.Args)
	}

	fin, err := os.Open(flag.Arg(0))
	if err != nil {
		log.Fatal(err)
	}
	defer fin.Close()

	_, err = io.Copy(os.Stdout, fin)
	if err != nil {
		log.Fatal(err)
	}
}

This is a Go program that reads a file and prints its contents to standard output. Here's how it works:

1. The Usage function sets the usage string for the program to be printed when the program is run with incorrect arguments.
2. flag.Parse() parses the command-line arguments and sets the values of the corresponding flag variables.
3. flag.NArg() returns the number of non-flag arguments.
4. If flag.NArg() is not exactly 1, log.Fatalf() prints an error message and exits the program.
5. os.Open(flag.Arg(0)) opens the file specified in the first non-flag argument.
6. defer fin.Close() arranges for the file to be closed after the function completes or if there's an error.
7. io.Copy(os.Stdout, fin) copies the contents of the file to standard output.
8. If there is an error opening the file or copying its contents, log.Fatal(err) prints an error message and exits the program.

Overall, the program provides a simple command-line interface to read the contents of a file and print it to the console.

lool