Consider the following ghostscript command invoked form the command line on windows.
"C:\Program Files\gs\gs9.23\bin\gswin64c.exe" -sDEVICE=mswinpr2 -dORIENT1=false -dNOPROMPT -dNOPAUSE -dPrinted -dBATCH -dNOPAUSE -dNOSAFER -q -dFIXEDMEDIA -dDEVICEWIDTHPOINTS=398 -dDEVICEHEIGHTPOINTS=157 -dNOPAGEPROMPT -dQUIET -dNumCopies=1 -sOutputFile="\\spool\BWLAB05" "c:\print\download\133679.pdf"
This command works great. The print comes out and there is no pop up box. Now I add the following.
-c "<</Orientation 2>>setpagedevice"
to the above command to make
"C:\Program Files\gs\gs9.23\bin\gswin64c.exe" -sDEVICE=mswinpr2 -c "<</Orientation 2>>setpagedevice" -c "quit" -dORIENT1=false -dNOPROMPT -dPrinted -dBATCH -dNOPAUSE -dNOSAFER -q -dFIXEDMEDIA -dDEVICEWIDTHPOINTS=398 -dDEVICEHEIGHTPOINTS=157 -dNumCopies=1 -sOutputFile="\\spool\BWLAB05" "c:\print\download\133679.pdf"
the print window appears. I have changed no other part of the command. What is causing this to happen? How can I stop the print window appearing?
The order of operands to Ghostscript is important. Especially when using the -c switch, which introduces PostScript to be executed.
Effectively you are running two commands here:
-sDEVICE=mswinpr2 -c "<</Orientation 2>>setpagedevice" -c "quit"
-dORIENT1=false -dNOPROMPT -dPrinted -dBATCH -dNOPAUSE -dNOSAFER -q -dFIXEDMEDIA -dDEVICEWIDTHPOINTS=398 -dDEVICEHEIGHTPOINTS=157 -dNumCopies=1 -sOutputFile="\\spool\BWLAB05" "c:\print\download\133679.pdf"
As soon as it hits the -c Ghostscript stops processing the command line, and runs the PostScript. At this point we have not yet encountered the -dNOPROMPT, and as you haven't (yet) set the printer, Ghostscript doesn't know what printer to use so , unsurprisingly, the printer popup appears.
Ghostscript carries on processing the remainder of the command line as PostScript until it reaches a -f, or in fact any switch beginning -. You haven't put a -f in there, but I would very strongly recommend that you do. You also don't need to put a secopnd -c, once you've started processing the command line as PostScript it continues, until you stop it. I also suspect that you really don't want the quit in there. That terminates the interpreter, which means the changes you've introduced via setpagedevice will be discarded, because the interpreter returns to the default state.
After processing the content of the -c, Ghostscript carries on and processes the remainder of the command line. This time there's a -dNOPROMPT so you don't get prompted.
I would expect that this:
"C:\Program Files\gs\gs9.23\bin\gswin64c.exe" -sDEVICE=mswinpr2 -dORIENT1=false -dNOPROMPT -dPrinted -dBATCH -dNOSAFER -q -dFIXEDMEDIA -dDEVICEWIDTHPOINTS=398 -dDEVICEHEIGHTPOINTS=157 -dNumCopies=1 -sOutputFile="\\spool\BWLAB05" -c "<</Orientation 2>>setpagedevice" -f "c:\print\download\133679.pdf"
would work much better. Note your initial command line has a duplicate NOPAUSE and specifies both NOPROMPT and NOPAGEPROMPT (you don't need NOPAGEPROMPT if you set NOPROMPT, and you don't need either if you set NOPAUSE).
Finally I would urge you not to use -dNOSAFER, while it currently has no effect (because that's the default setting) we will soon be making SAFER the default and setting -dNOSAFER will substantially reduce your security when running files.
You should really use -dSAFER right now. There are a number of CVEs against this, and proof of concepts circulating right now which can have undesirable effects on your computer (running arbitrary executables, opening, writing, deleting files etc) if you don't use -dSAFER. If you don't know why you want -dNOSAFER, then use -dSAFER instead.
Oh, you should also upgrade to the current version, 9.27, the version you are using is a year old.