The std/sys module provides access to system-level operations including environment variables, command-line arguments, working directory, and process control.
Import
Functions
env_get
Get the value of an environment variable by name. Returns void if the variable is not set.
let value = sys.env_get(name);
Name of the environment variable to retrieve
The value of the environment variable, or void if not set
import "std/sys";
let home = sys.env_get("HOME");
if home != void {
println(f"Home directory: {home}");
} else {
println("HOME not set");
}
let user = sys.env_get("USER");
if user != void {
println(f"Current user: {user}");
}
args
Get all command-line arguments as a list of strings. The first element is the program name, followed by any arguments passed to the script.
let arguments = sys.args();
List of command-line arguments. Index 0 is the program name, indices 1+ are user arguments
import "std/sys";
let args = sys.args();
println(f"Program: {args[0]}");
if len(args) > 1 {
println(f"Arguments: {args[1..]}");
for arg in args[1..] {
println(f" - {arg}");
}
} else {
println("No arguments provided");
}
$ walrus script.walrus input.txt output.txt
Program: script.walrus
Arguments: ["input.txt", "output.txt"]
- input.txt
- output.txt
cwd
Get the current working directory as a string. Returns void if the working directory cannot be determined.
let directory = sys.cwd();
The absolute path to the current working directory, or void on error
import "std/sys";
let current = sys.cwd();
if current != void {
println(f"Working directory: {current}");
}
exit
Exit the program immediately with the specified status code. By convention, 0 indicates success and non-zero values indicate errors.
Exit status code. Use 0 for success, non-zero for errors
This function never returns; it terminates the program
import "std/sys";
let args = sys.args();
if len(args) < 2 {
println("Usage: walrus script.walrus <filename>");
sys.exit(1); // Exit with error code
}
println("Processing file...");
// ... do work ...
sys.exit(0); // Exit successfully
Usage patterns
Environment configuration
Read configuration from environment variables:
import "std/sys";
import "std/io";
// Get config path from environment
let config_path = sys.env_get("APP_CONFIG");
if config_path == void {
config_path = "default.conf"; // Fallback to default
}
if io.file_exists(config_path) {
let config = io.read_file(config_path);
println(f"Loaded config from {config_path}");
}
Command-line argument parsing
Process command-line arguments:
import "std/sys";
import "std/io";
let args = sys.args();
if len(args) < 3 {
println(f"Usage: {args[0]} <input> <output>");
sys.exit(1);
}
let input_file = args[1];
let output_file = args[2];
if !io.file_exists(input_file) {
println(f"Error: Input file '{input_file}' not found");
sys.exit(1);
}
let content = io.read_file(input_file);
io.write_file(output_file, content);
println(f"Copied {input_file} to {output_file}");
import "std/sys";
println("System Information:");
println(f" Working Directory: {sys.cwd()}");
let user = sys.env_get("USER");
if user != void {
println(f" Current User: {user}");
}
let home = sys.env_get("HOME");
if home != void {
println(f" Home Directory: {home}");
}
let path = sys.env_get("PATH");
if path != void {
println(f" PATH: {path}");
}
Graceful error handling
Validate inputs and exit with appropriate codes:
import "std/sys";
import "std/io";
let args = sys.args();
if len(args) != 2 {
println("Error: Expected exactly one argument");
sys.exit(1);
}
let filename = args[1];
if !io.file_exists(filename) {
println(f"Error: File '{filename}' does not exist");
sys.exit(2);
}
let content = io.read_file(filename);
if len(content) == 0 {
println(f"Warning: File '{filename}' is empty");
sys.exit(3);
}
println(f"Successfully processed {filename}");
sys.exit(0);