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Command-line arguments are a common way to parameterize execution of programs. For example, go run hello.go uses run and hello.go as arguments to the go program.

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Accessing Arguments with os.Args

Go provides access to raw command-line arguments through the os.Args slice. The first value in this slice is always the path to the program itself, while os.Args[1:] contains the actual arguments passed to the program. 
package main

import (
	"fmt"
	"os"
)

func main() {

	// `os.Args` provides access to raw command-line
	// arguments. Note that the first value in this slice
	// is the path to the program, and `os.Args[1:]`
	// holds the arguments to the program.
	argsWithProg := os.Args
	argsWithoutProg := os.Args[1:]

	// You can get individual args with normal indexing.
	arg := os.Args[3]

	fmt.Println(argsWithProg)
	fmt.Println(argsWithoutProg)
	fmt.Println(arg)
}

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Running the Program

To experiment with command-line arguments, it’s best to build a binary with go build first: 
go build command-line-arguments.go
./command-line-arguments a b c d

[./command-line-arguments a b c d]
[a b c d]
c
The first element of os.Args is always the program name. Use os.Args[1:] to access only the user-provided arguments.

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Key Points

os.Args Structure

The first element (os.Args[0]) is the program path, followed by the actual arguments.

Array Indexing

Access individual arguments using standard slice indexing like os.Args[3].
Make sure to check the length of os.Args before accessing specific indices to avoid index out of bounds errors.

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Next Steps

For more advanced command-line processing with named flags and options, see Command Line Flags.

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