I've found this following routine useful.
Basically it allows me to just get nonblocking full lines of input
from a filehandle (using the select/vec solution - and heavily based
on tadman's code above).
# An non-blocking filehandle read that returns an array of lines read
# Returns: ($eof,@lines)
my %nonblockGetLines_last;
sub nonblockGetLines {
my ($fh,$timeout) = @_;
$timeout = 0 unless defined $timeout;
my $rfd = '';
$nonblockGetLines_last{$fh} = ''
unless defined $nonblockGetLines_last{$fh};
vec($rfd,fileno($fh),1) = 1;
return unless select($rfd, undef, undef, $timeout)>=0;
# I'm not sure the following is necessary?
return unless vec($rfd,fileno($fh),1);
my $buf = '';
my $n = sysread($fh,$buf,1024*1024);
# If we're done, make sure to send the last unfinished line
return (1,$nonblockGetLines_last{$fh}) unless $n;
# Prepend the last unfinished line
$buf = $nonblockGetLines_last{$fh}.$buf;
# And save any newly unfinished lines
$nonblockGetLines_last{$fh} =
(substr($buf,-1) !~ /[\r\n]/ && $buf =~ s/([^\r\n]*)$//)
? $1 : '';
$buf ? (0,split(/\n/,$buf)) : (0);
}
I've tested it with a pipe I opened using an IO::File, YMMV.
Example usage:
$fh = new IO::File;
open($fh,"$cmd 2>&1 |");
do {
($eof,@lines) = nonblockGetLines($fh);
foreach my $line ( @lines ) {
print "Pipe saw: [$line]\n";
}
} until $eof;
close $fh;
I don't know enough about vec() to know why tadman called it twice, don't
know if this is a race condition or if it's unneeded, and at this point
don't care enough to figure it out - I've got other code to write! :)
Enjoy!
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