how to capture exit value via pipe

[ku916]

I wrote a perl script that would read stdout and parse for particular
set of keywords, if found it will exit with error status.

sample cmd:

sqlplus user/wrong_password @somesql.sql | perl_filter.pl

perl_filter.pl is my script
since we passed in <wrong_password> into sqlplus, perl_filter.pl will
parse the stdout (from sqlplus) and find the keyword (i.e. error) and
exit with non-zero value

but the problem I'm having now is that when the parent command itself
errors out how can perl_filter.pl catch the exit value ($?) viva pipe
like:

sqlpus user/wrong_password @somesql.sql | perl_filter.pl

since there is no program called sqlpus, it will return non-zero exit
value, but perl_filter.pl would not detect any stdout keyword and it
will just exit and return success (zero) value.

any suggestions would be great help

Thanks

 

[J. Gleixner]

I wrote a perl script that would read stdout and parse for particular
set of keywords, if found it will exit with error status.

sample cmd:

perl_filter.pl is my script
since we passed in <wrong_password> into sqlplus, perl_filter.pl will
parse the stdout (from sqlplus) and find the keyword (i.e. error) and
exit with non-zero value

but the problem I'm having now is that when the parent command itself
errors out how can perl_filter.pl catch the exit value ($?) viva pipe
like:

since there is no program called sqlpus, it will return non-zero exit
value, but perl_filter.pl would not detect any stdout keyword and it
will just exit and return success (zero) value.

any suggestions would be great help

If there's nothing to read from STDIN, then that could be treated
as an error condition.

 

[xhoster]

I wrote a perl script that would read stdout and parse for particular
set of keywords, if found it will exit with error status.

sample cmd:

perl_filter.pl is my script
since we passed in <wrong_password> into sqlplus, perl_filter.pl will
parse the stdout (from sqlplus) and find the keyword (i.e. error) and
exit with non-zero value

but the problem I'm having now is that when the parent command itself
errors out how can perl_filter.pl catch the exit value ($?) viva pipe
like:

It appears that a shell is what is starting sqlpus, and thus it is the
shell's responsibility to deal with the error. If you want Perl to deal
with it, make Perl start the script in the first place:

open my $fh, "-|", 'sqlpus user/wrong_password @somesql.sql'
or do_something_with_errors($!,$?);

Maybe even using the 4 or more argument form of pipe open.

Or you could just assume that if STDIN is empty, then an error occurred,
but that seems like a pretty non-general and/or brittle solution.

Xho

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[ku916]

what are the "4 or more argument form of pipe open"?

is there no way to grab $? or $PIPIESTATUS in perl? I've tried
something like this (but does not work)

if ( $? != 0 || $PIPESTATUS[0] != 0 )
{
print "caught failed exit status\n";
exit 1;
}
else {
exit 0;
}

 

[xhoster]

what are the "4 or more argument form of pipe open"?

from perlipc:

Since Perl 5.8.0, you can also use the list form of "open"
for pipes : the syntax

open KID_PS, "-|", "ps", "aux" or die $!;

forks the ps(1) command (without spawning a shell, as
there are more than three arguments to open()), and reads
its standard output via the "KID_PS" filehandle. The cor-
responding syntax to write to command pipes (with "|-" in
place of "-|") is also implemented.

is there no way to grab $? or $PIPIESTATUS in perl?

For $?, yes, *if Perl started the command in the first place*.

I'm not aware of a built-in Perl variable named $PIPESTATUS.

Xho

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[ku916]

It appears that a shell is what is starting sqlpus, and thus it is the
shell's responsibility to deal with the error. If you want Perl to deal
with it, make Perl start the script in the first place:

open my $fh, "-|", 'sqlpus user/wrong_password @somesql.sql'
or do_something_with_errors($!,$?);

Maybe even using the 4 or more argument form of pipe open.

Or you could just assume that if STDIN is empty, then an error occurred,
but that seems like a pretty non-general and/or brittle solution.

Xho

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payment of page charges. This article must therefore be hereby marked
advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate
this fact.

I've tried grabbing PIPESTATUS inside my perl script but now luck,
why?
if ( $? != 0 || $PIPESTATUS[0] != 0 )
{
print "caught failed exit status\n";
exit 1;
}
else {
exit 0;
}

 

[xhoster]

On 18 Oct, 14:34, (e-mail address removed) wrote:

I've tried grabbing PIPESTATUS inside my perl script but now luck,
why?
if ( $? != 0 || $PIPESTATUS[0] != 0 )

If you explain why you think it *should* work, perhaps we can explain
why you are wrong to think that.

Perl DOES NOT HAVE a built-in variable named $PIPESTATUS or @PIPESTATUS,
as you would have found out if you used strict.

$ perl -le 'use strict; print $PIPESTATUS[0]'

Global symbol "@PIPESTATUS" requires explicit package name at -e line 1.
Execution of -e aborted due to compilation errors.

Xho

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