> From [EMAIL PROTECTED] Sun Jun 25 23:31:32 2000
> Date: Sun, 25 Jun 2000 22:28:31 -0700 (PDT)
> To: [EMAIL PROTECTED]
> Subject: Re: LPRng: HP DeskJet 930C anyone? How to determine capabilities?
> From: [EMAIL PROTECTED]
>
> from the quill of [EMAIL PROTECTED] on scroll
> <[EMAIL PROTECTED]>
> >
> > Actually, the 'dumbness' comes from the fact that there is
> > no way to request status information using PCL, so you might as
> > well not ask for it.
>
> I realize that. The printer model "pcl" only includes PCL capabilities
> and excludes PJL capabilities altogether. I understand that. What I am
> asking is whether there is an effective method of testing for the
> presence of any PJL at all if is so discovering (even if by trial and
> error) what commands are supported.
No. Sorry, been down that path and it runs over a cliff.
> OK. But under what circumstances does lpd know to whether to open
> read/write or write only? Presumably lpd is making a choice somewhere,
> somehow when it does the open.
if the :rw flag is set and the device is not a file then it opens it RW.
Now sockets are always RW, so even if you use FCNTL to get the
flags, you get a RW indication. However, sometimes the device
does not always return status information, so you have to tell
the lower levels that it does not. This is, as they say, a pain.
>
> > Now if anybody knows a way to find out the allowed operations
> > (or if it was open READ/WRITE/ or APPEND) using some system calls,
> > please tell me. Even if they are not portable, I will put them
> > into the code base.
>
> fcntl() will tell you what flags are set on an FD, including whether it
> is O_WRONLY or not. Here is a line from an strace of lpd on linux:
>
> fcntl(3, F_GETFL) = 0x1 (flags O_WRONLY)
>
> and if strace can determine that O_WRONLY so should lpd be able to.
>
> But I am sure you know all of this, so I must be missing something
> blindingly obvious.
No, perhaps not. I will look at this again. But it may only be on
Linux systems, which is still better than nothing.
Patrick
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