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Environmental Variables In Golang

  • Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer.
  • They are part of the environment in which a process runs.
    • For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process.
  • Examples of environment variables include:
    • PATH - a list of directory paths.
    • HOME (Unix-like) and USERPROFILE (Microsoft Windows) - indicate where a user's home directory is located in the file system.
    • HOME/{.AppName} (Unix-like) and APPDATA\{DeveloperName\AppName} (Microsoft Windows) - for storing application settings.
    • LOCALAPPDATA or PROGRAMDATA (shared between users) is used.
    • TERM (Unix-like) - specifies the type of computer terminal or terminal emulator being used
    • PS1 (Unix-like) - specifies how the prompt is displayed in the Bourne shell and variants.
    • MAIL (Unix-like) - used to indicate where a user's mail is to be found.
    • TEMP - location where processes can store temporary files
golang environmental variables

Go language program for environmental variables

package main

	import "os"
import "strings"
import "fmt"

	func main() {
// To set a key/value pair, use os.Setenv. To get a value for a key, use os.Getenv. This will return an empty string if the key isn’t present in the environment.
	    os.Setenv("FOO", "1")
    fmt.Println("FOO:", os.Getenv("FOO"))
    fmt.Println("BAR:", os.Getenv("BAR"))

//Use os.Environ to list all key/value pairs in the environment. This returns a slice of strings in the form KEY=value. You can strings.Split them to get the key and value. Here we print all the keys.

    for _, e := range os.Environ() {
        pair := strings.Split(e, "=")
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output for the above program

// Running the program shows that we pick up the value for FOO that we set in the program, but that BAR is empty.
	$ go run environment-variables.go
FOO: 1
// The list of keys in the environment will depend on your particular machine.
// If we set BAR in the environment first, the running program picks that value up
	$ BAR=2 go run environment-variables.go
FOO: 1
BAR: 2 

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