Want mdb -e
Currently mdb only exits one if it is unable to execute an expression for some reason or there is some syntax error. If however you have a dmcd which returns DCMD_ERR or DCMD_USAGE there is no programatic way to know of that. Having this would really great aid testing of things such as ::typedef. This work adds a -e option to mdb to evaluate an expression and if the dcmd returns something other than DCMD_OK, then the exit status will be one. If several dcmds are done in a row, e.g. '::help | ::foobar' then the exit status will be that of the last command.