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Re: IPC3 buffer limit problem

by zentara (Archbishop)
on Jan 03, 2006 at 15:12 UTC ( [id://520615]=note: print w/replies, xml ) Need Help??


in reply to IPC3 buffer limit problem

Update: Jan-03-2006

just tried to run this script again on my newer linux system with a 2.6.x kernel and Perl 5.8.7. Anyways, there seems to be a difference in the way pipes work, and the above script no longer works. Below is another version that does work. It includes an output-to-file, so you can compare the output to bc running in a terminal.

#!/usr/bin/perl use warnings; use strict; use IPC::Open3; require 'sys/ioctl.ph'; use FileHandle; # for testing output to compare to # bc's output, needed for autoflush $| = 1; #to write to a file to compare to bc's output open (OUT, "> $0.out") or die "$!\n"; OUT->autoflush(1); # I tested this with # "q @ 2" to generate errors # "123^12345" to generate big output # "123^23456" to generate huge output #interface to "bc" calculator my $pid = open3(\*WRITE, \*READ,\*ERROR,"bc"); #if \*ERROR is false, STDERR is sent to STDOUT while(1){ my($error,$answer,$rsize,$esize,$errortot,$answertot)=('','',0,0,'','' +); print "Enter expression for bc, i.e. 2 + 2\n"; chomp(my $query = <STDIN>); if(length($query) == 0){next} #removes empty input #send query to bc print WRITE "$query\n"; #this do loop waits and eliminates need for a delay to let bc output #It is NOT limited to 4060 bytes from bc, it keeps reading #until a semi-full buffer is sent, which signals end of output do { #see which filehandles have output from perldoc -q filehandle $esize = pack("L", 0); ioctl(\*ERROR, FIONREAD(), $esize) or die "Couldn't call ioctl: +$!\n"; $esize = unpack("L", $esize); print "esize-> $esize\n" unless ($esize < 1); $rsize = pack("L", 0); ioctl(\*READ, FIONREAD(), $rsize) or die "Couldn't call ioctl: $ +!\n"; $rsize = unpack("L", $rsize); print "rsize-> $rsize\n" unless ($rsize <1); #get the output from bc if($esize > 0){sysread(ERROR,$error,$esize); $errortot = $errorto +t.$error} # needed this line on older linuxes and Perl, the pipes worked diff +erent # if($rsize > 0){sysread(READ,$answer,$rsize); $answertot = $answe +rtot.$answer} # on newer kernels 2.6.x and Perl 5.8.7, this works if($rsize > 0){sysread(READ,$answer,4096); $answertot = $answerto +t.$answer} } until( ($esize > 0) or ( ($rsize > 0) and ($rsize < 4096) ) ); if(length($errortot) > 0){ print "\e[1;31m ERROR-> $errortot \e[0m \n" +} if(length($answertot) > 0){print "Output->$query = $answertot\n" } print OUT $answertot; } close OUT; waitpid($pid, 1); # It is important to waitpid on your child process, # otherwise zombies could be created.

I'm not really a human, but I play one on earth. flash japh

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