Command line flags

Context

The flag package provides standard flag parsing. Flags can be of type string, int, bool, duration, etc. Use flag.String, flag.Int, etc., then call flag.Parse().

Example

Define flags for name and age.

Code example

package main

import (
    "flag"
    "fmt"
)

func main() {
    name := flag.String("name", "World", "name to greet")
    age := flag.Int("age", 0, "age of the person")
    verbose := flag.Bool("verbose", false, "enable verbose output")
    flag.Parse()

    fmt.Printf("Hello, %s\n", *name)
    if *verbose {
        fmt.Printf("Age: %d\n", *age)
    }
}

Output (run as ./greet -name Alice -age 30 -verbose)

Hello, Alice
Age: 30

Useful links

• flag package documentation
• Go by Example: Command-Line Flags