The Way to Go/

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Reading Arguments from the Command-Line

Reading Arguments from the Command-Line

This lesson explains two packages of Go that let us read arguments from the command line.

We'll cover the following...

With the os package

The package os also has a variable os.Args of type slice of strings that can be used for elementary command-line argument processing, which is reading arguments that are given on the command-line when the program is started. Look at the following greetings-program:

package main
import (
"fmt"
"os"
"strings"
)

func main() {
  who := "Alice "
  if len(os.Args) > 1 {
    who += strings.Join(os.Args[1:], " ")
  }
  fmt.Println("Good Morning", who)
}

When we run this program, the output is: Good Morning Alice. The same output we get when we run it on the command-line as:

go run main.go

But, when we give arguments on the command-line like:

go run main.go John Bill Marc Luke

we get Good Morning Alice John Bill Marc Luke as an output.

When there is at least one command-line argument, the slice os.Args[] takes in the arguments (separated by a space), starting from index 1 since os.Args[0] contains the name of the program, os_args ...