Care has been taken that MIDAS and the Host Operating System (DCL for VMS and
Bourne or C-shell for Unix) co-exist
smoothly and complement each other.
Migration from one environment to the other is simple:
If you are in the MIDAS environment, type BYE to switch back to the Host System.
If you have returned to the host environment from a MIDAS session, (indicated by the $-prompt in VMS, and by $ or % in Unix), type GOMIDAS (in VMS) or gomidas (in Unix) to revive MIDAS. The status of the keywords and the command buffer of the stopped
MIDAS session are preserved - if you want to start afresh, use INMIDAS (VMS)
or inmidas (Unix) again.
You may also use host commands directly inside MIDAS by preceding them with `$'. For instance,
Midas 027> $DIR (in VMS) or
Midas 027> $ls (in Unix)
will display the contents of the current directory.
Please, note, that currently this mode of operation will only invoke Bourne shell commands in Unix, not C-shell or Kornshell commands. To execute C-shell (or any other Shell) commands you have to insert them in a Bourne shell script which has as the first line: ! /bin/csh, or ! /bin/ksh, etc.
NoteIf you work on a VMS system, beware of DCL command procedures:
DCL modifies command I/O streams when executing a procedure. This causes problems for the interprocess communication inside MIDAS. When executing a DCL procedure via $ @ `procedure' the correct settings will be maintained inside MIDAS.
However assigning a symbol MIMI to the command above and then executing the DCL procedure by just typing $ MIMI will lead to disaster from which only a BYE and subsequent GOMIDAS will get you going again.
The output from MIDAS commands can be redirected to ASCII files
enabling easy combination of MIDAS and host commands. E.g.
Midas 123> READ/DESCR myimage * >dsc.dat
will send all the output from the READ/DESCR command to the ASCII file dsc.dat (created in your current work directory) which can then be used by any host command. For example,
Midas 124> $EDIT dsc.dat (in VMS) or
Midas 124> $vi dsc.dat (in Unix)
Midas 125> STATISTICS/IMAGE myimage >dsc.datNoteThis mechanism is pretty much like the one used in Unix with the exception that there should be no space between the > and the output file name. Furthermore, this output redirection also works on VMS.