Re: Perl DBI sets $SIG{PIPE} to 'IGNORE'

Damian Keefe wrote:
> Hi Folks
>
> $DBI::VERSION = "1.609"
> perl, v5.8.8 built for x86_64-linux-thread-multi
> SHELL=/bin/tcsh
>
> I'm not sure if this should be considered a bug in DBI or elsewhere, 
> but it has unpleasant consequences. Somewhere in the bowels of DBI, 
> SIGPIPE gets set to 'IGNORE'. It remains in this state after 
> disconnect(). If you then launch a second script using backticks and 
> this script contains a line like
>
> my $first_line = `grep -v '#' $filename|head -n 1`; # to get the first 
> non-comment line
>
> the shell which is invoked inherits the SIGPIPE = 'IGNORE' state. This 
> causes a
> grep: writing output: Broken pipe
> error as the grep tries to write to the head process which has exited.
>
> It took me a while to work this out because of the way perl populates 
> the %SIG hash. It appears it only populates it once from the system 
> when it is first used in the script. If you run the script below with 
> the first print statement commented out you get
>
> connected to dk_funcgen_classify_59_MEF
> SIGPIPE=IGNORE
>
> If you uncomment the first print statement you get
>
> SIGPIPE=UNDEF
> connected to dk_funcgen_classify_59_MEF
> SIGPIPE=UNDEF
>
> However, behind the scenes, something has changed SIGPIPE to IGNORE 
> and the %SIG hash has not been updated.
>
> (my workaround is to explicitly reset SIGPIPE to 'DEFAULT' in the 
> second script)
>
> cheers
>
> Damian
>
>
I suspect you'll find its your driver library that ignores SIGPIPE as 
AFAIK, DBI does not.
Oracle's OCI library changes some signal dispositions for sure and 
sometimes SIGPIPE/SIGCHLD.

Martin

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