system

System-level operations and information

Import

_ <- fat.system

Types

Name Signature Brief
CommandResult (code: ExitCode, out: Text) Return type of capture

Constants

  • successCode, 0: ExitCode
  • failureCode, 1: ExitCode

Methods

Name Signature Brief
args (): List/Text Return list of args passed from shell
exit (code: Number): * Exit program with provided exit code
getEnv (var: Text): Text Get env variable value by name
shell (cmd: Text): ExitCode Execute cmd in shell, return exit code
capture (cmd: Text): CommandResult Capture the output of cmd execution
fork (args: List/Text, out: Text = ø) Start background process, return PID
kill (pid: Number): Void Send SIGTERM to process by PID
getLocale (): Text Get current locale setting
setLocale (_: Text): Number Set current locale setting
getMacId (): Text Get machine identifier (MAC address)
blockSig (enabled: Boolean): Void Block SIGINT, SIGHUP and SIGTERM

Usage Notes

Heads Up!

It is important to exercise caution and responsibility when using the getEnv, shell, capture, fork and kill methods. The system library provides the capability to execute commands directly from the operating system, which can introduce security risks if not used carefully.

To mitigate potential vulnerabilities, avoid using user input directly in constructing commands passed to these methods. User input should be validated to prevent command injection attacks and other security breaches.

Handling signals

When a Ctrl+C interruption occurs, the FatScript interpreter's main thread captures the signal and initiates a cleanup process. During this process, if it detects any running Workers, it will forcibly terminate them to prevent the application from hanging.

For applications requiring more refined control over the shutdown process, FatScript provides an option to block the default signal handling by setting system.blockSig(true). When enabled, the interpreter will not capture Ctrl+C. This requires you to implement your own termination mechanisms, possibly via curses.readKey or another method.

Other Limitations (multithreading)

While the methods in this library support a variety of programming tasks, they are not optimized for interleaved usage within asynchronous Workers. When initiating processes from within threads, opt for shell/capture methods, or exclusively use fork/kill. Mixing these two method pairs in multithreaded applications can result in unpredictable behavior.

on each call, shell/capture will set SIGCHLD to its default behavior, while fork will ignore this signal to try to avoid zombie processes

fork

The out parameter allows redirecting the standard output (stdout) to a specified output file. If you wish to discard this output, you can use "/dev/null" as an argument.

get/set locale

The fry interpreter will attempt to initialize LC_ALL locale to C.UTF-8 and if that locale is not available on the system tries to use en_US.UTF-8, otherwise, the default locale will be used.

See more about locale names.

locale configuration applies only to application, and is not persisted after fry exits

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