OS Module¶

The os module provides operating system functions for environment variables, process control, platform detection, file I/O, and system commands.

Import¶

import os

API Reference¶

Environment Variables¶

Function	Returns	Description
`getenv(key)`	`str`	Get env var (empty if not set)
`setenv(key, val)`	`none`	Set env var

Platform & System Info¶

Function	Returns	Description
`platform()`	`str`	Platform ID: `"darwin"`, `"linux"`, `"windows"`
`name()`	`str`	OS name: `"macOS"`, `"Linux"`, `"Windows"`
`arch()`	`str`	CPU architecture: `"arm64"`, `"x86_64"`
`hostname()`	`str`	System hostname
`cpu_count()`	`int`	Number of CPU cores
`home_dir()`	`str`	User's home directory (cross-platform)
`temp_dir()`	`str`	System temp directory (`/tmp`, `%TEMP%`)

Process¶

Function	Returns	Description
`getpid()`	`int`	Current process ID
`exit(code)`	`none`	Exit with status code
`sleep_ms(ms)`	`none`	Sleep for given milliseconds

Directory¶

Function	Returns	Description
`getcwd()`	`str`	Current working directory
`chdir(path)`	`int`	Change directory (0 = success)

Command Execution¶

Function	Returns	Description
`system(cmd)`	`int`	Run shell command, returns exit code
`which(name)`	`str`	Find executable in PATH (empty if not found)

Usage Examples¶

import os

def main() -> int:
    # Platform detection
    print(f"Running on {os.name()} ({os.arch()})")
    print(f"Hostname: {os.hostname()}")
    print(f"CPUs: {os.cpu_count()}")

    # Home and temp directories
    print(f"Home: {os.home_dir()}")
    print(f"Temp: {os.temp_dir()}")

    # Find executables
    let python = os.which("python3")
    if len(python) > 0:
        print(f"Python at: {python}")

    # Environment
    os.setenv("MY_APP_PORT", "8080")
    let port = os.getenv("MY_APP_PORT")
    print(f"Port: {port}")

    # Working directory
    let cwd = os.getcwd()
    print(f"CWD: {cwd}")
    0

File I/O¶

Read and write files with simple one-line calls:

Reading Files¶

import os

let content = os.read_file("config.json")
print(content)

Returns empty string if the file doesn't exist or can't be read.

Writing Files¶

# Write (creates or overwrites)
os.write_file("output.txt", "Hello, Desi!")

# Append to existing file
os.append_file("log.txt", "New log entry\n")

Both return 0 on success, -1 on error.

File I/O API Reference¶

Function	Returns	Description
`read_file(path)`	`str`	Read entire file as string
`write_file(path, data)`	`int`	Create/overwrite file (0 = success)
`append_file(path, data)`	`int`	Append to file (0 = success)

File System¶

Check paths, get file info, and manage directories:

import os

# Check if paths exist
print(os.exists("myfile.txt"))    # true/false
print(os.is_file("myfile.txt"))   # true if regular file
print(os.is_dir("mydir"))         # true if directory

# File size
let size = os.file_size("data.bin")  # bytes, or -1 on error

# Directory operations
os.mkdir("new_folder")
let files = os.listdir(".")       # ["file1.txt", "file2.desi", ...]
os.rmdir("empty_folder")

# File operations
os.rename("old.txt", "new.txt")
os.remove("unwanted.txt")

File System API Reference¶

Function	Returns	Description
`exists(path)`	`bool`	True if path exists
`is_file(path)`	`bool`	True if regular file
`is_dir(path)`	`bool`	True if directory
`file_size(path)`	`int`	Size in bytes (-1 on error)
`mkdir(path)`	`int`	Create directory (0 = success)
`rmdir(path)`	`int`	Remove empty directory (0 = success)
`remove(path)`	`int`	Delete file (0 = success)
`rename(old, new)`	`int`	Rename file/dir (0 = success)
`listdir(path)`	`list[str]`	List directory contents (excludes `.` and `..`)

Complete Example¶

import os

def main() -> int:
    # Platform detection
    print(f"Running on {os.name()} ({os.arch()})")
    print(f"Home: {os.home_dir()}")
    print(f"Temp: {os.temp_dir()}")

    # File I/O
    os.write_file("/tmp/hello.txt", "Hello from Desi!")
    let content = os.read_file("/tmp/hello.txt")
    print(content)

    # Find executables
    let ls = os.which("ls")
    print(f"ls found at: {ls}")

    # Directory listing
    let files = os.listdir(".")
    print(f"Files in current dir: {files}")

    # Cleanup
    os.remove("/tmp/hello.txt")
    0