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Golang program to parse a command line flag of string type

Here, we are going to learn how to parse a command line flag of string type in Golang (Go Language)?
Submitted by Nidhi, on April 12, 2021 [Last updated : March 04, 2023]

Parsing a command line flag of string type in Golang

Problem Solution:

In this program, we will pass the string type flag from the command line during program execution and then print the value of the specified flag on the console screen.

Program/Source Code:

The source code to parse a command line flag of string type is given below. The given program is compiled and executed on the ubuntu 18.04 operating system successfully.

Golang code to parse a command line flag of string type

// Golang program to parse a
// command line flag of string type

package main

import "fmt"
import "flag"

func main() {
	colorPtr := flag.String("color", "red", "a string")

	fmt.Println("Default value of color: ", *colorPtr)
	flag.Parse()

	fmt.Println("Value of color flag: ", *colorPtr)
}

Output:

$ go run hello.go -color=green

Default value of color:  red
Value of color flag:  green

Explanation:

In the above program, we declare the package main. The main package is used to tell the Go language compiler that the package must be compiled and produced the executable file. Here, we imported the fmt, flag packages then we can use a function related to the fmt and flag package.

In the main() function, we passed string type flag from the command line during program execution and then parse command line flag "color" using flag.String(), flag.Parse() functions and printed the default and actual value of the specified flag on the console screen.

Golang Command-Line Arguments Programs »

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