[OS X TeX] Emacs 22.92, %! and TeXShop

Herbert Schulz herbs at wideopenwest.com
Fri Jan 26 17:25:33 EST 2007

On Jan 26, 2007, at 4:07 PM, Chris Goedde wrote:

> On Jan 26, 2007, at 3:41 PM, Frank STENGEL wrote:
>> Isn't it
>> %!PS
>> That should be the first four bytes of a postscript file?
> No, historically %! was sufficient to identify a postscript file.  
> Files that conform to the Postscript document structure convention  
> are supposed to start with %!PS-Adobe-3.0 (for example, for PS3),  
> but %! is a valid first line for a postscript file. In fact,  
> postscript files that are valid but don't conform to all the  
> structural conventions are supposed to start with %! (or at least  
> not the full %!PS-Adobe-3.0).
> --
> Chris Goedde

The PostScript Language Reference Manual (I've got the old 1985  
edition) and it says

``The very first line of every PostScript program (whether it is  
conforming or nonconforming) should be a comment that begins with the  
characters `%!'.''

and, in the next paragraph, further says

``If the PostScript program is conforming, the remainder of the first  
line (after the `%!') should be a version identifier for the  
structuring conventions that the file obeys. ... (i.e., the first 11  
characters of the program ar `%!PS-Adobe-') ...''

So everyone is correct. Of course all the logic I've seen presented  
is still wrong: just because all PostScript files should start with ` 
%!' (maybe `%!PS...') doesn't mean that all files that start with ` 
%!' (or even `%!PS...') must be PostScript files.

Good Luck,

Herb Schulz
(herbs at wideopenwest.com)

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