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< article >
< h1 > env</ h1 >
< p > The < code > env</ code > module provides access to environment variables for reading, writing, and deleting values.</ p >
< pre >< code > import "env" for Environment</ code ></ pre >
< h2 > Environment Class</ h2 >
< div class = "class-header" >
< h3 > Environment</ h3 >
< p > Environment variable access</ p >
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< h3 > Static Methods</ h3 >
< div class = "method-signature" >
< span class = "method-name" > Environment.get</ span > (< span class = "param" > name</ span > ) → < span class = "type" > String|null</ span >
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< p > Gets the value of an environment variable.</ p >
< ul class = "param-list" >
< li >< span class = "param-name" > name</ span > < span class = "param-type" > (String)</ span > - Name of the environment variable</ li >
< li >< span class = "returns" > Returns:</ span > Value of the variable, or null if not set</ li >
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< pre >< code > var home = Environment.get("HOME")
System.print(home) // /home/alice
var missing = Environment.get("UNDEFINED_VAR")
System.print(missing) // null</ code ></ pre >
< div class = "method-signature" >
< span class = "method-name" > Environment.set</ span > (< span class = "param" > name</ span > , < span class = "param" > value</ span > )
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< p > Sets an environment variable.</ p >
< ul class = "param-list" >
< li >< span class = "param-name" > name</ span > < span class = "param-type" > (String)</ span > - Name of the environment variable</ li >
< li >< span class = "param-name" > value</ span > < span class = "param-type" > (String)</ span > - Value to set</ li >
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< pre >< code > Environment.set("MY_APP_DEBUG", "true")
System.print(Environment.get("MY_APP_DEBUG")) // true</ code ></ pre >
< div class = "method-signature" >
< span class = "method-name" > Environment.delete</ span > (< span class = "param" > name</ span > )
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< p > Deletes an environment variable.</ p >
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< li >< span class = "param-name" > name</ span > < span class = "param-type" > (String)</ span > - Name of the environment variable to delete</ li >
</ ul >
< pre >< code > Environment.delete("MY_APP_DEBUG")
System.print(Environment.get("MY_APP_DEBUG")) // null</ code ></ pre >
< h3 > Static Properties</ h3 >
< div class = "method-signature" >
< span class = "method-name" > Environment.all</ span > → < span class = "type" > Map</ span >
</ div >
< p > Returns a map of all environment variables.</ p >
< pre >< code > var env = Environment.all
for (entry in env) {
System.print("%(entry.key) = %(entry.value)")
}</ code ></ pre >
< h2 > Examples</ h2 >
< h3 > Reading Configuration from Environment</ h3 >
< pre >< code > import "env" for Environment
var host = Environment.get("APP_HOST")
if (host == null) host = "localhost"
var port = Environment.get("APP_PORT")
if (port == null) port = "8080"
var debug = Environment.get("APP_DEBUG") == "true"
System.print("Starting server on %(host):%(port)")
System.print("Debug mode: %(debug)")</ code ></ pre >
< h3 > Default Values Pattern</ h3 >
< pre >< code > import "env" for Environment
class Config {
static get(name, defaultValue) {
var value = Environment.get(name)
return value != null ? value : defaultValue
}
static getInt(name, defaultValue) {
var value = Environment.get(name)
if (value == null) return defaultValue
return Num.fromString(value)
}
static getBool(name, defaultValue) {
var value = Environment.get(name)
if (value == null) return defaultValue
return value == "true" || value == "1"
}
}
var timeout = Config.getInt("TIMEOUT", 30)
var verbose = Config.getBool("VERBOSE", false)
var logFile = Config.get("LOG_FILE", "/var/log/app.log")
System.print("Timeout: %(timeout)s")
System.print("Verbose: %(verbose)")
System.print("Log file: %(logFile)")</ code ></ pre >
< h3 > Setting Environment for Subprocesses</ h3 >
< pre >< code > import "env" for Environment
import "subprocess" for Subprocess
Environment.set("NODE_ENV", "production")
Environment.set("PORT", "3000")
var result = Subprocess.run("node server.js")
System.print(result.stdout)</ code ></ pre >
< h3 > Listing All Environment Variables</ h3 >
< pre >< code > import "env" for Environment
System.print("=== Environment Variables ===")
var env = Environment.all
var keys = []
for (entry in env) {
keys.add(entry.key)
}
keys.sort()
for (key in keys) {
System.print("%(key) = %(env[key])")</ code ></ pre >
< h3 > Checking Required Environment Variables</ h3 >
< pre >< code > import "env" for Environment
var required = ["DATABASE_URL", "API_KEY", "SECRET_KEY"]
var missing = []
for (name in required) {
if (Environment.get(name) == null) {
missing.add(name)
}
}
if (missing.count > 0) {
System.print("Missing required environment variables:")
for (name in missing) {
System.print(" - %(name)")
}
Fiber.abort("Configuration error")
}
System.print("All required environment variables are set")</ code ></ pre >
< h3 > Temporary Environment Modification</ h3 >
< pre >< code > import "env" for Environment
var originalPath = Environment.get("PATH")
Environment.set("PATH", "/custom/bin:" + originalPath)
System.print("Modified PATH for operations...")
Environment.set("PATH", originalPath)
System.print("Restored original PATH")</ code ></ pre >
< h3 > Database Connection String from Environment</ h3 >
< pre >< code > import "env" for Environment
var dbUrl = Environment.get("DATABASE_URL")
if (dbUrl != null) {
System.print("Using database: %(dbUrl)")
} else {
var host = Environment.get("DB_HOST")
if (host == null) host = "localhost"
var port = Environment.get("DB_PORT")
if (port == null) port = "5432"
var name = Environment.get("DB_NAME")
if (name == null) name = "myapp"
var user = Environment.get("DB_USER")
if (user == null) user = "postgres"
dbUrl = "postgres://%(user)@%(host):%(port)/%(name)"
System.print("Constructed database URL: %(dbUrl)")
}</ code ></ pre >
< div class = "admonition note" >
< div class = "admonition-title" > Note</ div >
< p > Environment variables modified with < code > set</ code > or < code > delete</ code > only affect the current process and any child processes. They do not modify the parent shell's environment.</ p >
</ div >
< div class = "admonition tip" >
< div class = "admonition-title" > Tip</ div >
< p > For configuration that may vary between environments (development, staging, production), use environment variables. This follows the twelve-factor app methodology.</ p >
</ div >
< div class = "admonition warning" >
< div class = "admonition-title" > Warning</ div >
< p > Never log or print sensitive environment variables like API keys, passwords, or secrets. Use them directly in your application without exposing their values.</ p >
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