Example
Go standard library provides package flag that helps with parsing flags passed to program.
Note that flag package doesn't provide usual GNU-style flags. That means that multi-letter flags must be started with single hyphen like this:
-exampleflag , not this: --exampleflag. GNU-style flags can be done with some 3-rd party package.
package main
import (
"flag"
"fmt"
)
func main() {
// basic flag can be defined like this:
stringFlag := flag.String("string.flag", "default value", "here comes usage")
// after that stringFlag variable will become a pointer to flag value
// if you need to store value in variable, not pointer, than you can
// do it like:
var intFlag int
flag.IntVar(&intFlag, "int.flag", 1, "usage of intFlag")
// after all flag definitions you must call
flag.Parse()
// then we can access our values
fmt.Printf("Value of stringFlag is: %s\n", *stringFlag)
fmt.Printf("Value of intFlag is: %d\n", intFlag)
}
flag does help message for us:
$ ./flags -h
Usage of ./flags:
-int.flag int
usage of intFlag (default 1)
-string.flag string
here comes usage (default "default value")
Call with all flags:
$ ./flags -string.flag test -int.flag 24
Value of stringFlag is: test
Value of intFlag is: 24
Call with missing flags:
$ ./flags
Value of stringFlag is: default value
Value of intFlag is: 1
