Child processes

The exact v0.3 declarations and focused examples are indexed in the standard-library reference.

std::process::command owns command construction, child handles, pipe endpoints, and exit status. std::process::errors contains the portable error family used at this host boundary.

@imports :: lib::std::process::command;

childCommand := command::Command::init("flecha".string());
childCommand.arg("--version".string());

child, spawnError := childCommand.spawn();
if spawnError != none {
    return spawnError;
}

status, waitError := child.wait();
if waitError != none {
    return waitError;
}

Command owns its executable, arguments, environment overrides, and optional working directory. Adding one of those values transfers or copies ownership as declared by the method signature. Failure to grow command storage leaves the previous command usable. spawn() borrows the finished configuration and returns a ChildProcess owning the native process and configured pipe handles.

Spawning, pipe reads and writes, and wait() cross the operating-system boundary and may block. tryWait() is the nonblocking status probe. Closing a pipe or child handle is explicit where the API exposes close; normal scope cleanup closes any remaining owned native resource exactly once. A child exit code is data in ExitStatus, not a Flecha error. Spawn, pipe, wait, invalid configuration, and unsupported-host failures use ProcessError or the wider error return declared by the operation.

ExitStatus distinguishes normal exit from signal or other abnormal host termination. Numeric details are host-derived and should not be treated as a portable signal enumeration. Argument quoting, executable lookup, inherited environment behavior, and available process features follow the documented Windows or POSIX runtime boundary; no shell is inserted automatically.

The workspace_guard north-star builds a command from captured CLI arguments, starts it only after verification, waits for it, and maps normal and abnormal termination into stable application exit behavior.