Re: [Process] Hardcoding the command for shell

From: degski (degski_at_[hidden])
Date: 2020-03-11 12:24:37

https://en.cppreference.com/w/cpp/utility/program/system

On Tue, 10 Mar 2020 at 08:22, Frederick Gotham via Boost-users <
boost-users_at_[hidden]> wrote:

> At the command line on most operating system, you can pipe a file into
> another program and then pipe out into a third program.
>
> For example: Take a file from the hard disk, decrypt it, and then unzip it:
>
>     openssl rc4-40 -salt -d -pass pass:MyPassword <
> /home/frederick/monkey.tar.gz.encrypted > tar -zxf -
>
> I realise, when using Boost::Process, that we can tie the input and
> output streams of child processes together using 'ipstream', but I
> want to be able to take the above command and give it directly to the
> operating system (or to the 'shell').
>
> On Linux x64 and armhf(32-Bit), the following works:
>
>     child c(search_path("sh"),
>         "-c",
>         "openssl rc4-40 -salt -d -pass pass:MyPassword <
> /home/frederick/monkey.tar.gz.encrypted > tar -zxf -"
>     );
>
> But should I have to hardcode "sh" and "-c" into my program like that?
> I have tried using "shell" like this:
>
>     child c( "openssl rc4-40 -salt -d -pass pass:MyPassword <
> /home/frederick/monkey.tar.gz.encrypted > tar -zxf -",
>        shell
>     );
>
> but this doesn't work on either Linux x64 or armhf(32-Bit). I thought
> the whole point of "shell" was that you didn't have to hardcode "sh
> -c" in Linux or "cmd /c" in MS-Windows.
>
> Also if you do some web-searching for how to run a batch file in
> MS-Windows using boost::process, you'll see that everyone is doing
> this:
>
>     context ctx;
>     ctx.environment = self::get_environment();
>     child c = launch("cmd", "/c batch.bat", ctx);
>
> Should it be necessary to hardcode "cmd /c" like that? Shouldn't this
> all be taken care of by "boost::process::shell"?
>
> Frederick
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> Boost-users mailing list
> Boost-users_at_[hidden]
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>

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