Re: feature request: self join from stdin

2019-10-23 Thread Bernhard Voelker 
On 2019-10-21 08:28, Rasmus Borup Hansen wrote:
> [...] e.g. this hangs on my machine:
> 
> mkfifo fifo && seq -s , 2 | tee fifo | join -j2 - fifo | paste -s && rm 
> fifo

okay, then better use a regular file, and join that with itself:

  $ seq -s , 2 > x

  $ join -j2 x x  | paste -s
   1,2,3,4,5,6,[...]

Have a nice day,
Berny

Re: feature request: self join from stdin

2019-10-21 Thread Rasmus Borup Hansen 
> On 20 Oct 2019, at 19.33, Bernhard Voelker  wrote:
> 
> On 2018-11-25 17:45, furrymc...@lippydanger.jumpingcrab.com wrote:
>> Please consider a self join from stdin in coreutils.
>> 
>> $ seq 3 | join -j2 - - | paste -s
>> 1 1   1 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3
> 
> What about tee'ing into a 'fifo' which is read again by join?
> 
> $ mkfifo fifo \
> && seq 3 | tee fifo | join -j2 - fifo | paste -s \
> && rm fifo
> 1 11 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3
> 
> Have a nice day,
> Berny
> 

This will hang if the lines get so long that the fifo is filled before it can 
be emptied, e.g. this hangs on my machine:

mkfifo fifo && seq -s , 2 | tee fifo | join -j2 - fifo | paste -s && rm fifo

Best,

Rasmus

Re: feature request: self join from stdin

2019-10-20 Thread Bernhard Voelker 
On 2018-11-25 17:45, furrymc...@lippydanger.jumpingcrab.com wrote:
> Please consider a self join from stdin in coreutils.
> 
> $ seq 3 | join -j2 - - | paste -s
>  1 1   1 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3

What about tee'ing into a 'fifo' which is read again by join?

 $ mkfifo fifo \
 && seq 3 | tee fifo | join -j2 - fifo | paste -s \
 && rm fifo
 1 1 1 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3

Have a nice day,
Berny

Re: feature request: self join from stdin

2019-10-20 Thread Andreas Schwab 
On Okt 20 2019, Nomen Nescio  
wrote:

> Do you think the following coproc solves the problem?
> A join or paste prints expected results.
> Curiously cat or tac will block the process.
> Can you explain why join/paste finish the process whereas cat/tac block it?

Because join and paste simultanously read both files, whereas cat and
tac read one file after the other.  Then tee blocks on stdout because
nobody drains the pipe buffer.

Andreas.

-- 
Andreas Schwab, sch...@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Re: feature request: self join from stdin

2019-10-20 Thread Nomen Nescio 


Do you think the following coproc solves the problem?
A join or paste prints expected results.
Curiously cat or tac will block the process.
Can you explain why join/paste finish the process whereas cat/tac block it?

# ii  bash   4.4-5amd64GNU Bourne Again SHell
# ii  coreutils  8.26-3   amd64GNU core utilities
seq 10 |
{
coproc { cat; } && exec 3<&${COPROC[0]}- 4<&${COPROC[1]}-
coproc { cat; } && exec 5<&${COPROC[0]}- 6<&${COPROC[1]}-
tee >(cat >&4) > >(cat >&6) & exec 4>&- 6>&-

join <(cat <&3) <(cat<&5)## GOOD
# paste <(cat <&3) <(cat<&5) ## GOOD
# cat <(cat <&3) <(cat <&5)   ## BAD
# tac <(cat <&3) <(cat<&5)   ## BAD
# cat <(cat <&3) & cat <(cat <&5) &  ## GOOD
wait
}