can PERL just quit?

[gupr1980]

We call perl scripts from within a IBM tool. The way we do this is make a call to JAVA runtime process and run a perl command on the server, the java process returns the output/error of the PERL script. In our testing we found at times the java process just hangs. Looks like the PERL script doesnt throw any output or error and just quits?? code is below

=cut
use strict;
use warnings;

my $infilename = $ARGV[0];
my $outfilename = $ARGV[1];
my $header = $ARGV[2];
my $readoffset = $ARGV[3];
my $readreccnt = $ARGV[4];
my $inreccnt = 0;
my $outreccnt = 0;
print "StartTime:";
print scalar localtime(time);
open my $INFILE, '<', $infilename;
seek $INFILE, $readoffset, 0;
open my $OUTFILE, '>>', $outfilename;

if ($artheader ne 'NOHDR'){
    $artheader =~ tr/'^'/' '/;
    print $OUTFILE "$header\n";
    $outreccnt++;
}

READLOOP: while (<$INFILE>){
    $inreccnt++;
    if ($inreccnt > $readreccnt){
        last READLOOP;
    }
    s/^HHH\.S.*//s;
    s/^EEE\.S.*//s;
    s/^0000\S{4}\s{2}//;
    print $OUTFILE $_;
    $outreccnt++;
}

close $INFILE;
close $OUTFILE;

print ",EndTime:";
print scalar localtime(time);
print ",\n";
print "InFileName:";
print $infilename;
print ",ReadOffset:";
print $readoffset;
print ",ReadRecordCnt:";
print $readreccnt;
print ",OutFileName:";
print $outfilename;
print ",OutRecordCnt:";
print $outreccnt;
print ",\n";
print "HeaderLen:";
print (length $artheader);
print ",HeaderData:";
print $header;
print ",\n";

earlier i had use autodie but then took it out. I am new to PERL, is there a case where a PERL script can just quit and not throw any. Should i use "use autodie"?

[Eily]

Your code doesn't compile, because $artheader isn't defined anywhere. I saw that by putting your code in a file called test.pl and running perl -c test.pl. This checks the syntax of the program without actually running it so you can try perl -c on your file without side effects.

Edit: this means you should try and see why your tool doesn't give you any feedback on this error. The compilation error message should be sent to the standard error output, just as any error occuring during runtime.

[LanX]

Good catch... but a framework running Perl scripts (like eg Tivoli) should be able to report compilation problems...(?)

[Eily]

I guess it should yes. At least gupr1980 knows the problem is not on perl's side. I'm going to edit my post.

[Anonymous Monk]

It's just a typo. I was trying to change artheader to header for this post. No compile errors.

[LanX]

Isn't this rather an OS question?

Are you sure the Perl script terminated?

Maybe try

• logging a heartbeat
• overwriting $SIG{__DIE__}
• putting debug code into END{block}
(the later 2 might (?) be redundant :)

I'm always inclined to blame JAVA though...

[LanX]

Regarding autodie :

Those frameworks normally use quite antique Perl versions and installing modules shouldn't be easy.

But the documentation for open already has it all:

 open(my $fh, "<", "input.txt") 
    or die "cannot open < input.txt: $!";

and so on for print and close

you said your JAVA-process hangs...

...IF the Perl process was really erminated I can't see a sane reason for this, except that the JAVA process is faulty.

Consider file system problems or race conditions...

Otherwise call IBM support.

[boftx]

Since you are not testing the return values of open or anything else, I would definitely have use autodie; in place.

[gupr1980]

i get Can't locate autodie.pm on Linux. How can i get this? I have autodie.pm on my windows workstation, is there a way i can copy it over to Linux server?

[Laurent_R]

Hmm, surprising... The autodie module has been a standard Perl package for quite a while. Which version of Perl are you running?

[boftx]

You can get it from metaCPAN: autodie

I would normally say get it from CPAN, but they have been down a lot lately. :(

[runrig]

You don't need autodie. You can rewrite your code so that it checks for errors and reports the reason for failure, e.g.:

open my $INFILE, '<', $infilename or die "Cannot open $infilename: $!"
+;
seek $INFILE, $readoffset, 0 or die "Cannot seek: $!";
open my $OUTFILE, '>>', $outfilename or die "Cannot open $outfilename:
+ $!";

[sundialsvc4]

Another way to do it would be to put an eval block around more-or-less “all of it,” then check the result afterward.   If the process throws a runtime error, it will be caught here, and you can output something that will help you to resolve the problem.   In any case, you can force the Perl script to generate some STDERR output in all cases, which is what the Java wrapper seems to be looking for.

Sometimes I define a variable outside of the eval-block, called $doing_what which I populate with some string (initially "nothing"), changing it along the way, specifically to use it in any caught error-messages.   Whatever the string is found to contain will at least indicate that the failure occurred very-shortly after the statement which set the variable to this particular value.   While it might be a low-tech way to do it, it works well.   Just be very sure that no statement which assigns a value to that string can itself encounter a runtime error, and that the variable is never undef.

[Anonymous Monk]

Putting autodie sounds simpler, will it throw an error on all cases?

[blue_cowdawg]

is there a case where a PERL script can just quit

No, slaves can't quit. They have to be sold. :-P