[Gambas-user] Gambas app calling a PERL Script which calls a program (rtmpdump)

[Rob]

Before I begin, I should tell you that I tried to duplicate your problem 
but got the list of programmes in my Gambas app just fine using your EXEC 
command, adjusted to find the copy of get_iplayer I just downloaded. I 
created a form with a button and a textarea and wrote this in its class:

PUBLIC SUB Button1_Click()

  DIM sType AS String
  DIM sOutput AS String

  stype = "TV"

  EXEC ["/home/schmoe/build/get_iplayer-2.80/get_iplayer", "--force", "--
type=" & sType] TO sOutput
  
  TextArea1.Text = sOutput

END

Please excuse the word wrapping above and below. The result of clicking the 
button was the textarea being filled with the following:

get_iplayer v2.80, Copyright (C) 2008-2010 Phil Lewis
  This program comes with ABSOLUTELY NO WARRANTY; for details use --
warranty.
  This is free software, and you are welcome to redistribute it under 
certain
  conditions; use --conditions for details.

Matches:
1:	1911 Centenary Lecture - 1. David Lloyd George, BBC Parliament, 
Factual,History,Politics,TV, default
2:	1911 Centenary Lecture - 3. Nancy Astor, BBC Parliament, 
Factual,History,Politics,TV, default
3:	1911 Centenary Lecture - 5. Aneurin Bevan, BBC Parliament, 
Factual,History,Politics,TV, default
[about 792 more lines...]

So what I have to say here is just theoretical. I'm using get_iplayer 2.80, 
Gambas 2.16.

On Friday 02 September 2011 02:43, John Rose wrote:
> EXEC ["get_iplayer", "--force", "--type=" & sType] TO sOutput
> where sType & sOutput are both strings with sType having the value "TV".
> This is equivalent to "get_iplayer --force --type="TV" run in a Gnome
> Terminal except that the output to StdOut is placed in sOutput. This
> command works fine in a Gnome Terminal or even with >Output.txt keyed in
> at the end of the command so that the output goes to a file Output.txt.

Successfully redirecting the output may not be quite the same thing as EXEC 
to a variable in Gambas, as outlined below.

> get_iplayer is a very complex PERL script which I do NOT want to amend.
> get_iplayer involves calling rtmpdump. rtmpdump can be executed in a
> Gnome Terminal. I do not even know what language rtmpdump is written in.

I'm familiar with rtmpdump, having compiled it myself a few times. It's 
just C, but in this case that's probably not relevant.

To expand upon something Ian said in his reply (it's probably not 
specifically a password prompt issue since you're able to redirect stdout 
successfully), it may be that your version of rtmpdump and/or get_iplayer 
tries to open a TTY (interactive terminal).  I didn't see anything obvious 
in the current version of get_iplayer or my copy of rtmpdump that should do 
that, but it's almost 10,000 lines of code and the symptoms fit. It would 
work fine in a terminal, even if you redirect input and output, but not 
when run from another process outside of a terminal.  

I ran into the same problem years ago when writing a Gambas program for a 
client that needed to ssh somewhere.  Benoit has made a lot of improvements 
since then. Try something like this:

EXEC ["get_iplayer", "--force", "--type=" & sType] FOR INPUT OUTPUT 

...

PUBLIC SUB Process_Read
  DIM tmp as String
  READ #LAST, tmp, lof(LAST)
  sOutput = sOutput & tmp ' sOuput
END

INPUT OUTPUT simulates a tty when executing the process. I have no way of 
testing this since it works for me as is, and since it's been a few years 
since I did a Gambas project I'm not even sure that Read event syntax is 
right. But I hope it's enough to point you in a helpful direction.

Rob