Re: Question regarding /proc/<pid>/fd and pipes

[Jan Engelhardt <jengelh@linux01.gwdg.de>]

>
>>   I know that the symlinks in the /proc/<pid>/fd directory point to
>> bogus filenames for pipes (i.e. 'pipe:[64682]') and am wondering if
>> every process that reads and writes from that pipe will share the same
>> bogus symlink name.
>

It is not really bogus. And it is not really real at the same time.
This is how it works AFAIU: pipes get created in pipefs (cat 
/proc/filesystems) (as do sockets in sockfs), and their dentry IS named 
"pipe:[46682]". You just can't see it because 1. you are prevented from 
mounting pipefs, 2. there are no readdir/etc. functions for pipefs 
implemented ATM.

>>   In essence, I'm wondering if there's any way to list all of the pid's
>> of processes using an anonomous pipe.
>
Hm. Do you mean list "all pids of procs using an anynymous pipe" or
"list all pids [...]" using an anonymous pipe... :)

AFAICS, the first is not possible; the latter is (a fork-and-exec 
thing) is something different.


Jan Engelhardt
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