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[_Command-line flags_](http://en.wikipedia.org/wiki/Command-line_interface#Command-line_option) are a common way to specify options for command-line programs. For example, in `wc -l` the `-l` is a command-line flag. 

    






    
    
        
    

    






    
    
package main

    






    
    
        
    

    






    
    
         Go provides a `flag` package supporting basic command-line flag parsing. We'll use this package to implement our example command-line program.
    
import (

    






    
    
	"flag"

    






    
    
	"fmt"

    






    
    
)

    






    
    
        
    

    






    
    
func main() {

    






    
    
        
    

    






    
    
         Basic flag declarations are available for string, integer, and boolean options. Here we declare a string flag `word` with a default value `"foo"` and a short description. This `flag.String` function returns a string pointer (not a string value); we'll see how to use this pointer below.
    
	wordPtr := flag.String("word", "foo", "a string")

    






    
    
        
    

    






    
    
         This declares `numb` and `fork` flags, using a similar approach to the `word` flag.
    
	numbPtr := flag.Int("numb", 42, "an int")

    






    
    
	boolPtr := flag.Bool("fork", false, "a bool")

    






    
    
        
    

    






    
    
         It's also possible to declare an option that uses an existing var declared elsewhere in the program. Note that we need to pass in a pointer to the flag declaration function.
    
	var svar string

    






    
    
	flag.StringVar(&svar, "svar", "bar", "a string var")

    






    
    
        
    

    






    
    
         Once all flags are declared, call `flag.Parse()` to execute the command-line parsing.
    
	flag.Parse()

    






    
    
        
    

    






    
    
         Here we'll just dump out the parsed options and any trailing positional arguments. Note that we need to dereference the pointers with e.g. `*wordPtr` to get the actual option values.
    
	fmt.Println("word:", *wordPtr)

    






    
    
	fmt.Println("numb:", *numbPtr)

    






    
    
	fmt.Println("fork:", *boolPtr)

    
word: foo
numb: 42
fork: false







    
    
	fmt.Println("svar:", svar)

    
svar: bar







    
    
	fmt.Println("tail:", flag.Args())

    
tail: []







    
    
}

    






    
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