I thought

int main(string[] args)
{
    import std.stdio;
    write(`Press enter to continue: `);
    stdout.flush;
    auto line = readln();
    writeln("Read ", line);
    return 0;
}

would function as a good prompting but it doesn't.

I outputs the string given to write *after* I've pressed return. Why?

On Sun, Sep 28, 2014 at 02:16:29PM +0000, "Nordlöw" via Digitalmars-d-learn wrote:
> I thought
> 
> int main(string[] args)
> {
>     import std.stdio;
>     write(`Press enter to continue: `);
>     stdout.flush;
>     auto line = readln();
>     writeln("Read ", line);
>     return 0;
> }
> 
> would function as a good prompting but it doesn't.
> 
> I outputs the string given to write *after* I've pressed return. Why?

It's an OS limitation. If you're on Posix, you need to switch your terminal to cbreak mode, otherwise the program doesn't actually receive any data until after you press Return. I'm not sure what the Windows equivalent is, but a similar thing happens there -- the input line is buffered by the OS and the program doesn't see it until Return is pressed.

You might be interested in Adam Ruppe's terminal.d library, that handles such low-level details for you:

	https://github.com/adamdruppe/arsd/blob/master/terminal.d


T

-- 
People who are more than casually interested in computers should have at least some idea of what the underlying hardware is like. Otherwise the programs they write will be pretty weird. -- D. Knuth

On Sunday, 28 September 2014 at 14:48:03 UTC, H. S. Teoh via Digitalmars-d-learn wrote:
> On Sun, Sep 28, 2014 at 02:16:29PM +0000, "Nordlöw" via Digitalmars-d-learn wrote:
>> I thought
>> 
>> int main(string[] args)
>> {
>>     import std.stdio;
>>     write(`Press enter to continue: `);
>>     stdout.flush;
>>     auto line = readln();
>>     writeln("Read ", line);
>>     return 0;
>> }
>> 
>> would function as a good prompting but it doesn't.
>> 
>> I outputs the string given to write *after* I've pressed return. Why?
>
> It's an OS limitation. If you're on Posix, you need to switch your
> terminal to cbreak mode, otherwise the program doesn't actually receive
> any data until after you press Return. I'm not sure what the Windows
> equivalent is, but a similar thing happens there -- the input line is
> buffered by the OS and the program doesn't see it until Return is
> pressed.

That's not his problem though - he doesn't see "Press enter to continue" in the terminal before he enters text.

However, I can't reproduce it with DMD master on Linux, it works for me as intended.

On Sunday, 28 September 2014 at 15:36:17 UTC, Marc Schütz wrote:
> However, I can't reproduce it with DMD master on Linux, it works for me as intended.

My fault. I was too clever and call the program through a wrapper to rdmd I call rdmd-dev containing

#!/usr/bin/env bash

# See also: http://forum.dlang.org/thread/qvznmjdmdvkyyrkhbkgy@forum.dlang.org

if type ddemangle &> /dev/null; then
    exec rdmd -L--export-dynamic -color=on -g -gs -debug $* 2>&1 | ddemangle
else
    exec rdmd -L--export-dynamic -color=on -g -gs -debug $* 2>&1
fi

The piping to ddemangle messed things up...

Thanks anyway.

On Sunday, 28 September 2014 at 16:01:06 UTC, Nordlöw wrote:
> The piping to ddemangle messed things up...
>
> Thanks anyway.

Does anybody have a better solution to this? I would still like the linker error output be ddemangled...

On Sunday, 28 September 2014 at 16:02:44 UTC, Nordlöw wrote:
> On Sunday, 28 September 2014 at 16:01:06 UTC, Nordlöw wrote:
>> The piping to ddemangle messed things up...
>>
>> Thanks anyway.
>
> Does anybody have a better solution to this? I would still like the linker error output be ddemangled...

You can redirect stderr to ddemangle:

    rdmd ... 2> >( ddemangle )