RE: [Groff] File Locking

[Ted Harding]

On 13-Mar-08 08:45:32, Robert Thorsby wrote:
> I've finally started one of those rainy day projects. I'm rewriting my 
> Business Letterhead shell script.
> 
> It's progressed to the stage where, after I've written the draft 
> letter, the script opens the input file in the text editor du jour and 
> also opens the resulting postscript file in gv. Every time I hit "Save"
> in the text editor the script automagically re-runs the input file 
> through groff and, of course, the "watch" switch in gv automagically 
> reloads the updated postscript file. The result is a sort of groff 
> version of WYSIWYG.
> 
> However, I don't know what would happen if I used the text editor 
> "Save" twice in quick succession. In other words what would happen if 
> my text editor is amending the input file on the "second" occasion at 
> the same time as groff is processing it as a result of the "first" 
> save?
> 
> Can anyone tell me what is likely to happen? I have no idea how to 
> create the problem deliberately.
> 
> TIA,
> Robert Thorsby

I run exactly the same kind of script. I very much doubt if it matters.
Groff will take the file as it finds it, and for most input files
will read it in very quickly -- you would have to move pretty fast
to re-save a changed file before groff finishes reading the first
version.

However, even if the file changes while groff is still reading it,
I think the worst that would happen is that you end up with an
output file (PS) which was invalid. Then gv would give you a
warning message to that effect. If that happened, all you would
need to do is hit "Save" again. Groff would re-read the file,
re-make the PS output, and gv would re-read that since it is
in "watch" mode. So you would be back on the rails.

Hoping that helps!
Ted.

--------------------------------------------------------------------
E-Mail: (Ted Harding) <address@hidden>
Fax-to-email: +44 (0)870 094 0861
Date: 13-Mar-08                                       Time: 09:43:39
------------------------------ XFMail ------------------------------