Path: utzoo!news-server.csri.toronto.edu!rutgers!rochester!pt.cs.cmu.edu!o.gp.cs.cmu.edu!andrew.cmu.edu!jj1h+ From: jj1h+@andrew.cmu.edu (Joseph Jackson) Newsgroups: comp.lang.postscript Subject: Re: How can I tell if a file is "postscript" Message-ID: Date: 12 Mar 91 01:07:53 GMT References: <1448@vidiot.UUCP> <449@heaven.woodside.ca.us>, <1460@vidiot.UUCP> Organization: Academic Computing, Carnegie Mellon, Pittsburgh, PA Lines: 45 In-Reply-To: <1460@vidiot.UUCP> Excerpts from netnews.comp.lang.postscript: 7-Mar-91 Re: How can I tell if a fil.. Vidiot@vidiot.UUCP (1572) > Two of us looked at the TranScript spooler and neither of us saw anything that > the filters did that made it run enscript (or whatever) to turn text into > PostScript. So, that left the printer doing the work. But, if the printer > doesn't do the work, then what piece of TranScript is doing the work. Yeah, it's a rather hidden feature. The lpd sends the print job through all the necessary filters and as a last step calls "pscomm" to pipe the output over the serial line to the printer. "pscomm" has some intelligence built in to it which isn't obvious. "pscomm" looks at the first few bytes of the input stream looking for the "%!" PostScript magic. If it doesn't find it, it will call "enscript" to convert the (assumedly text) file to PostScript. You can change what program is called by setting the PSTEXT variable in the .options file which is located in the spool directory for the given queue. Here's one way of looking at it: this feature provides some degree of compatibility with the old days of simple line printers. Think of how many things would break if you suddenly needed to specify an lpr switch when queuing straight text. Things like "ls | lpr" wouldn't work any more. Another feature allows TranScript to handle both face-up and face-down printers. "pscomm" can be configured to call a page reversal filter for selected printers. It uses the same "psrev" command which is normally made available to users. At my site, reversal is the default. For newer page-up printers, I add the line "REVERSE=" to the associated .options file to avoid unnecessary page reversal. Check out the file psint.sh for more details on .options file. In normal TranScript installations, all of the filters listed in the printcap are actually hard-links to psint.sh. That script invokes the .options file. Joe Jackson Distributed Workstation Services Carnegie Mellon University Internet: jj1h+@andrew.cmu.edu Bitnet: jj1h+@ANDREW AT&Tnet: (412) 268-8799