os and filepath Packages
Environment variables, paths, and OS interaction
os.Args — Command-Line Arguments
os.Args holds the command-line arguments. os.Args[0] is the program name:
package main
import ("fmt"; "os")
func main() {
fmt.Println("Program:", os.Args[0])
if len(os.Args) < 2 {
fmt.Println("Usage: program <name>")
os.Exit(1)
}
fmt.Printf("Hello, %s!\n", os.Args[1])
}os.Getenv and os.Setenv
Read and write environment variables:
package main
import ("fmt"; "os")
func main() {
// Read env var (returns "" if not set)
home := os.Getenv("HOME")
fmt.Println("HOME:", home)
// Set env var
os.Setenv("APP_ENV", "production")
fmt.Println(os.Getenv("APP_ENV")) // production
// Get with default pattern:
port := os.Getenv("PORT")
if port == "" { port = "8080" }
fmt.Println("Port:", port)
}All lessons in this course
- fmt and strings Packages
- strconv, math and sort
- time Package Essentials
- os and filepath Packages