tcl: capture output from "exec diff" which returned non-zero -

I know it is common to use when executing non-zero executing orders ... but how do I get it What is the output in that situation?

To be specific, I want to do something like "hold {exec diff fileA fileB} ret". The files are different and the rate value is 1. Do I need to act differently, produce differences, detailed differences but I believe that "cat (exec ...) mistake" practice does not provide it, okay?

Can anyone suggest this work? Are TCL-Biltin commands to separate the file? (I think it is possible to redirect the output to the file and then read the file ... are there any other options?)

Thanks!

From a recent project of mine:

  set status [Hold {Executive $ file1 $ $ 2 diff} result] If {$ status == 0} {say "$ file1 and $ 2 are equal"} elseif {$ status == 1} {say "** $ File1 and $ 2 are different ** "puts" **************************************************************************** **************************************************************************************************** **** ************************* ********* *********************************************************************************************** ********* "else {puts stderr" ** diff status exited with $ position ** "stderr puts" *********** ***** ******************* ************** ***** ******************* ******************************************************************************* ************** "}  

Bottom line, when the file is separated, the situation is 1 and the difference in the result is the difference in output it happens. At the end of the DIF output I get "hair process looks unusually" In my case I have not removed it, but it should be very easy to do.