expr is a small Go package for parsing environment variables from expressions with support for default values. It allows developers to easily retrieve environment variables or provide fallback values in case the variables are not defined.

Features

• Parse environment variables in the format ${VAR:default}.
• Provides fallback to default values if the environment variable is not defined.
• Supports simple string returns when no environment variables are used.

Installation

To install this package, use:

go get github.com/numih/expr

Usage

Importing the Package

import "github.com/numih/expr/env"

Parse Environment Variables

The Parse function evaluates expressions in the format ${VAR:default}, where VAR is the name of the environment variable and default is the fallback value if the variable is not defined.

package main

import (
	"fmt"
	"github.com/numih/expr/env"
)

func main() {
	// Set environment variable VAR="value" for this example.
	value := env.Parse("${VAR:default}")
	fmt.Println(value)  // Output: value if VAR is set, "default" otherwise
}

Examples

1. If VAR is defined:

   env.Parse("${VAR:default}") // Output: value of VAR

2. If VAR is not defined:

   env.Parse("${VAR:default}") // Output: "default"

3. No environment variable placeholder:

   env.Parse("foo") // Output: "foo"

4. If no default value is provided:

   env.Parse("${VAR}") // Output: value of VAR if set, otherwise ""