THANKS TO ALL: Passing huge args to system call

bubulik has asked for the wisdom of the Perl Monks concerning the following question:

I am making a system call with a huge sized argument. Here is the call:

 !system ("perl", $perl_file, $comp, $warn_list_arg); or die "Program 
+exit";
[download]

where: $warn_list_arg at times contains about 8000+ strings, each string consisting about 60+ chars. This arg is delimited such that the invoked Perl process can unmarshall these args.

For a small sized $warn_list_arg, the call executes OK. For larger sizes such as 8000+ strings, it fails. Here are some specs:

Exit value: 255 ($! >> 8)
Signal num: 0 ($! & 127)
Core dump: 0 ($! & 128)

Is there a size limit on the buffer containing the args? How might I be able to pass such a big arg?

BTW: i resorted to this method of passing args since passing an array/list to the system call failed to pass the args on to the invoked process. Or is there some way to pass arrays in a system call?

Thnx for any suggestion/help.

Thanks to all u folks for yr replies: sleepingsquirrel nothingmuch davido eclark ccn Creating the process via a filehandle was the trick for me! BBK

Edit by castaway, reinserted original question

Comment on THANKS TO ALL: Passing huge args to system call Download Code

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Re: Passing huge args to system call by ccn (Vicar) on Aug 05, 2004 at 19:06 UTC
You can pass your $warn_list_arg to STDIN of your $perl_file `open(SCRIPT, "\| perl $perl_file $comp") or die "can't run $perl_file: $!"; print SCRIPT $warn_list_arg; close(SCRIPT) or die "can't close $perl_file: $!";` [download] see perlopentut, open	[reply] [d/l]
Re: Passing huge args to system call by davido (Cardinal) on Aug 05, 2004 at 19:10 UTC
Maybe you could open a pipe to the second process, instead of invoking a system call to it. Or, save the large array as a file, and pass the filename to the second process. Also, you've got a problem with the snippet you posted. The semicolon after the system call terminates the sentence, so to speak. So the "`or die...`" portion is its own separate statement. You meant to say: `! system ( "perl", $perl_file, $comp, $warn_list_arg) or die "Program +exit";` [download] As for how to open a pipe, see perlopen and perlopentut. Dave	[reply] [d/l] [select]
Re: Passing huge args to system call by eclark (Scribe) on Aug 05, 2004 at 19:06 UTC
I dont know what the problem is, but have you considered passing $warn_list_arg as lines to STDIN? Such as: `open FH, "\|perl $perl_file $comp"); for (@warn_list) { print FH $_ . "\n"; } close FH;` [download] You'll have to modify `$perl_file` to read them from <STDIN> instead of @ARGV.	[reply] [d/l] [select]
Re: Passing huge args to system call by nothingmuch (Priest) on Aug 05, 2004 at 19:45 UTC
Afaik no kernel but HURD does not impose a software level hard limit on the number of arguments. On darwin, IIRC, the buffer is at most 64K in length. I think Linux is in the same ballpark. These may be defaults to kernel params, or even sysctlable, but there is a limit, and it isn't very big. I would suggest following on the advice that others gave you, to open a pipe. I would do it with a pipe to self, or by piping to $^X: `defined(my $pid = open my $child, "\|-") or die "$!"; if ($pid){ # parent print $child "$args"; } else { #child my $args = <STDIN>; } # or for an exec, at least run $^X instead of "perl": open my $child, "\|$^X", $scriptfile;` [download] -nuffin zz zZ Z Z #!perl	[reply] [d/l]
Re: THANKS TO ALL: Passing huge args to system call by saberworks (Curate) on Aug 06, 2004 at 00:13 UTC
You really shouldn't edit your comment to remove the question after it's answered, it can't help anyone that way.	[reply]
Re: Passing huge args to system call by sleepingsquirrel (Chaplain) on Aug 05, 2004 at 20:19 UTC
Probably not what you're looking for, but as long as you're calling perl (system "perl"...), why not... `@ARGV=split /\s+/, $warn_list_arg; unshift @ARGV, $comp; do $perl_file or die "Program Exit: $!\n";` [download] -- All code is 100% tested and functional unless otherwise noted.	[reply] [d/l]


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