我发现了这个问题,第一个答案包含一些示例代码,演示如何使用 Ada 代码启动可执行文件。可执行文件的输出将写入标准输出。
我有哪些选项可以读取可执行文件的输出以便在 Ada 中进行进一步解析/处理(例如逐行(?
如果您使用 GNAT,那么您可能需要查看GNAT.Expect
包中的Get_Command_Output
。下面是一个示例:
with Ada.Text_IO, GNAT.Expect;
procedure Main is
Command : constant String := "gnat";
Argument_1 : aliased String := "--version";
Input : constant String := "";
Status : aliased Integer := 0;
-- Execute the command and retrieve the output.
Output : String :=
GNAT.Expect.Get_Command_Output
(Command => Command,
Arguments => (1 => Argument_1'Unchecked_Access),
Input => Input,
Status => Status'Access,
Err_To_Out => False);
-- NOTE: Cheating with Unchecked_Access, OK for demo. You may want
-- to properly new and Free these strings (see Argument_List
-- type in package GNAT.OS_Lib).
begin
Ada.Text_IO.Put_Line (Output);
end Main;
程序在执行后返回:
$ ./main
GNAT Community 2019 (20190517-83)
Copyright (C) 1996-2019, Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
可以看出,结果以单个字符串的形式返回。你将不得不自己做线分裂。
更新
针对以下一些评论的更新。
如果您的目标是Windows平台,也可以考虑使用system
功能(另请参阅SO上的这篇文章(。引用函数参考:
system 函数将命令传递给命令解释器,后者将字符串作为操作系统命令执行。
这类似于程序cmd.exe
的功能。您可以通过将其输出重定向到文件(即使用 >
(来获取命令的输出,然后读回它。下面是一个示例:
with Ada.Text_IO;
with Ada.Text_IO.Unbounded_IO;
with Ada.Strings.Unbounded;
with Interfaces.C;
with Interfaces.C.Strings;
procedure Main is
use Ada.Strings.Unbounded;
Content : Unbounded_String := Null_Unbounded_String;
begin
-- Execute.
declare
use Interfaces.C;
use Interfaces.C.Strings;
function system (command : chars_ptr) return int
with Import, Convention => C, External_Name => "system";
command : chars_ptr := New_String("gnat --version > gnat_version.out");
result : int := system (command);
begin
-- Check value of result (omitted in this example).
Free(Command);
end;
-- Read.
declare
use Ada.Text_IO;
use Ada.Text_IO.Unbounded_IO;
Fd : File_Type;
begin
Open (Fd, In_File, "./gnat_version.out");
while not End_Of_File (Fd) loop
Content := Content
& Unbounded_String'(Get_Line (Fd))
& ASCII.CR & ASCII.LF; -- Restore the line break removed by Get_Line.
end loop;
Close (fd);
end;
-- Show.
Ada.Text_IO.Unbounded_IO.Put (Content);
end Main;