Avoid using Exec, instead use a helper that verifies results

[fingolfin]

The Exec command unfortunately does not allow checking the exit state of whatever it invoked. It also has other problems.

Instead I recommend to use the Process function directly, or possibly your own helper function based on it. Here is a simple example I've given to people before:

MyExec := function(cmd, args...)
 local result;
 result := rec(output := "");
 cmd := Filename(DirectoriesSystemPrograms(), cmd);
 result.status := Process( DirectoryCurrent( ), cmd, InputTextNone( ),
       OutputTextString( result.output, false ), args );
 return result;
end;

(I also propose a generally useful replacement for Exec in gap-system/gap#5103 -- feel free to copy it to this package and use it (but please only after renaming it) -- or perhaps a much simpler variant is enough for you, see e.g.