I found in the folder ...\scripts\ConteXt\ruby a file newtexexec.rb . I try it on some file and I obtain a good result.
But I have two problems :
1)after having write the resulting pdf file (after the first run) the hard disk seems to write or to read many seconds and then the program seems to run again
2)the following file :
**********************************
\startuseMPgraphic{fig}
draw unitsquare scaled 3cm ;
\stopuseMPgraphic

\starttext
\useMPgraphic{fig}
\stoptext
**********************************
gives a pdf but without the expected square
(the file gives a good result with texexec)
I am very curious about newtexexec.rb : I begin to learn Ruby
some weeks ago.
Thanks