[xmonad] how to redirect dynamicLogXinerama output to a FIFO/named pipe?

Lara Michaels laramichaels1978 at yahoo.com
Thu Jun 28 21:21:01 CEST 2012

Hi Brandon,

Many thanks for this. I will try to open the FIFO using the O_RDWR flag. My xmonad setup broke so badly when I upgraded my system to a more recent Ubuntu version that I am largely paralyzed work-wise because of this...


 From: Brandon Allbery <allbery.b at gmail.com>
To: Lara Michaels <laramichaels1978 at yahoo.com> 
Cc: "xmonad at haskell.org" <xmonad at haskell.org> 
Sent: Thursday, June 28, 2012 8:00 PM
Subject: Re: [xmonad] how to redirect dynamicLogXinerama output to a FIFO/named pipe?

On Thu, Jun 21, 2012 at 9:31 AM, Lara Michaels <laramichaels1978 at yahoo.com> wrote:

thank you for this, now I no longer get the error message upon starting xmonad. However, still nothing gets read by 'tail -f .xmonad-fifo'.

Sorry for the delay on this, things have been "interesting" here of late.

It belatedly occurred to me that this *is* a FIFO, and as such the reader has to open it first, with O_RDWR (or what Haskell calls ReadWriteMode) or it won't get hooked up properly.  (This is a POSIXism, and Linux at least is very strict about it; depending on the kernel version, you may see ENXDEV ("No such device or address") or what gets "opened" is a dummy node that will never successfully read or write data.) 
Is there some other way to the dynamicLogXinerama information so that I can display it on an applet/appindicator?

dynamicLogXinerama is not very flexible; the documentation notes this, and suggests an alternative which provides most of the same information while giving you flexibility (dynamicLogXinerama).

All in all, POSIX FIFOs are remarkably useless (and I'm still amazed POSIX found a way to make them even less useful than they were originally) and should probably be avoided.

brandon s allbery                                      allbery.b at gmail.com
wandering unix systems administrator (available)     (412) 475-9364 vm/sms
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