On Wed, Dec 4, 2013 at 10:51 PM, Roland Mainz <[email protected]> wrote:
> On Wed, Dec 4, 2013 at 10:39 PM, Vladimir Marek
> <[email protected]> wrote:
>> What a coincidence, I just stumbled upon another issue. I don't have fix
>> for this though ...
>>
>> The test script:
>>
>> $ cat c
>> #!/bin/ksh
>>
>> trap 'exit' EXIT
>>
>> (
>> yes | while read A; do
>> echo "$A"
>> STDERR=$(</dev/null)
>> done
>> )
>>
>> It should write infinite number of characters 'y'. But in reality it only
>> writes one 'y' and ten empty lines only.
>>
>> Also if you run the script as
>>
>> $ ./c | head
>>
>> It hangs. I don't know whether the two things (not reading and hanging) are
>> just a single issue or two different ones.
>>
>> I can reproduce this on both linux and solaris. On linux the ksh says
>>
>> $ echo $KSH_VERSION
>> Version AJM 93u+ 2012-08-01
>>
>> On Solaris
>> Version JM 93u 2011-02-08
>>
>> I'm just having a bad luck lately I guess ...
>
> I can reproduce the same issue with the following reduced testcase on
> Illumos B151a7/AMD64 with ast-ksh.2013-10-10/AMD64/64bit:
> -- snip --
> (
> for ((;;)) ; do print y ; done | while read A; do
> printf "%s\n" "$A"
> STDERR=$(</dev/null)
> done
> )
> -- snip --
>
> It seems to be an issue with the non-|fork()|'ing subshell code... if
> I force the code to use |fork()| for a subshell using the ulimit(1)
> builtin I get the correct output:
> -- snip --
> $ cat c.sh
> (
> ulimit -c 0
>
> for ((;;)) ; do print y ; done | while read A; do
> printf "%s\n" "$A"
> STDERR=$(</dev/null)
> done
> )
> $ ~/bin/ksh c.sh | head
> y
> y
> y
> y
> y
> y
> y
> y
> y
> y
> -- snip --
[snip]
Another workaround is to replace the $( < file ) construct with $( cat
< file ) ... note that ${ < file } has the same issues as $( < file )
in a subshell...
----
Bye,
Roland
--
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