Re: mkfifo and tee within a function

[Nathan Coulter]

>  From: Andreas Schwab <[SNIP]>
>  Subject: Re: mkfifo and tee within a function
>  Sent: 2006-11-28 15:09
>  
>  Nathan Coulter <[SNIP]> writes:
>  
>  > Could anyone please provide a few pointers on how to accomplish this, and 
> perhaps explain the results from the above examples?
>  
>  A process writing to a pipe that has no reader will receive EPIPE/SIGPIPE
>  and die thereof by default.  So it all depends on timing.
>  

I think that is true for an anonymous pipe, but not for a named pipe.  Timing 
is not the issue here.  A command which opens a named pipe for writing should 
block until a reader comes online.  In the following example, I get an error 
with "source', but not with "cat".  Why?

$>cmd_print () { mkfifo zout; tee zout & cat zout >/dev/null ; rm zout; }
$>cmd_print <<EOF
> date
> EOF
[1] 5263
date
[1]+  Done                    tee zout
$>cmd_print () { mkfifo zout; tee zout & source zout ; rm zout; }
$>cmd_print <<EOF
> date
> EOF
[1] 5267
$>date
tee: zout: Broken pipe

Finally, my workaround to this is:

$>cmd_print () { mkfifo zout; tee zout & eval "$(cat zout)" ; rm zout; }
$>cmd_print <<EOF
> date
> EOF
[1] 5274
date
Tue Nov 28 11:21:19 CST 2006
[1]+  Done                    tee zout
$>


-- 
Nathan Coulter