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% vim: ft=mercury ts=4 sw=4 et
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% Copyright (C) 1993-2012 The University of Melbourne.
% Copyright (C) 2013-2024 The Mercury team.
% This file is distributed under the terms specified in COPYING.LIB.
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%
% File: io.call_system.m.
%
% This module provides predicates to invoke commands via the shell
% of the underlying operating system.
%
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:- module io.call_system.
:- interface.

    % Invokes the operating system shell with the specified Command.
    % Result is either `ok(ExitStatus)', if it was possible to invoke
    % the command, or `error(ErrorCode)' if not. The ExitStatus will be 0
    % if the command completed successfully or the return value of the system
    % call. If a signal kills the system call, then Result will be an error
    % indicating which signal occurred.
    %
:- pred call_system(string::in, io.res(int)::out, io::di, io::uo) is det.

    % call_system_return_signal(Command, Result, !IO):
    %
    % Invokes the operating system shell with the specified Command.
    % Result is either `ok(ExitStatus)' if it was possible to invoke
    % the command or `error(Error)' if the command could not be executed.
    % If the command could be executed then ExitStatus is either
    % `exited(ExitCode)' if the command ran to completion or
    % `signalled(SignalNum)' if the command was killed by a signal.
    % If the command ran to completion then ExitCode will be 0 if the command
    % ran successfully and the return value of the command otherwise.
    %
:- pred call_system_return_signal(string::in, io.res(system_result)::out,
    io::di, io::uo) is det.

    % Interpret the child process exit status returned by system() or wait().
    %
:- func decode_system_command_exit_code(int) = io.res(io.system_result).

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