PIPE problem

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

what am i doing wrong? first program net.pl


my $count =0;
for (1.10){
warn "Writing line $_\n";
#!/usr/bin/perl
use strict;
$SIG{PIPE} = 'IGNORE';
open (PIPE,"| net2.pl") or die "Cannot open pipe:$!";
select PIPE ; $ |=1; select STDOUT;

my $count =0;
for (1.10){
warn "Writing line $_\n";
if (print PIPE "This is line number $_\n") {
$count ++;
}
else {
warn " An error occured during writing :$!";
last;
}
sleep 1;
}
close PIPE or die " Cannot close pipe : $!";
print "Wrote $count lines of text \n";
~
[download]

second program net2.pl

#!/usr/bin/perl
use strict;
for (1.3) {
last unless defined (my $line = <>);
warn " Read_three,got $line\n";
}
[download]

OUTPUT ./net.pl Writing line 1.1 Cannot close pipe : at ./net.pl line 19. 6 + Stopped (SIGTTIN) ./net2.pl &

Comment on PIPE problem Select or Download Code

Replies are listed 'Best First'.
Re: PIPE problem by borisz (Canon) on Jan 15, 2004 at 18:47 UTC
your program whould work, if you replace 1.3 with 1..3 and 1.10 with 1..10. .. is the range operator. And you may remove the first 3 lines from your example. Ahh and a typo on $ \|= 1; it should read $\| = 1; here the whole thing again. `#!/usr/bin/perl use strict; $SIG{PIPE} = 'IGNORE'; open( PIPE, "\|net2.pl" ) or die "Cannot open pipe:$!"; select PIPE; $\| = 1; select STDOUT; my $count = 0; for ( 1 .. 10 ) { warn "Writing line $_\n"; if ( print PIPE "This is line number $_\n" ) { $count++; } else { warn " An error occured during writing :$!"; last; } sleep 1; } close PIPE or die " Cannot close pipe : $!"; print "Wrote $count lines of text \n";` [download] And net2.pl `#!/usr/bin/perl use strict; for (1..3) { last unless defined (my $line = <>); warn " Read_three,got $line\n"; }` [download] Boris	[reply] [d/l] [select]
Re: PIPE problem by ysth (Canon) on Jan 15, 2004 at 18:45 UTC
The range operator is `..` , not `.` , so I think you you want `1..3` and `1..10`. Also, in your close PIPE or die, be aware that close on a pipe doesn't always set $!. perldoc -f close gives example: `close OUTPUT # wait for sort to finish or warn $! ? "Error closing sort pipe: $!" : "Exit status $? from sort";` [download] Update: changing both scripts to use .. instead of . and removing the extra stuff before #!/usr/bin/perl in net.pl gives this output: `$ perl -w net1.pl Writing line 1 Read_three,got This is line number 1 Writing line 2 Read_three,got This is line number 2 Writing line 3 Read_three,got This is line number 3 Writing line 4 An error occured during writing :Broken pipe at net1.pl line 14. Wrote 3 lines of text` [download] which looks to me like what you should be expecting. If you have other expectations, please share them so others can help you further. Update: also added a -w to net2.pl's shebang line	[reply] [d/l] [select]
Re: PIPE problem by pg (Canon) on Jan 15, 2004 at 18:39 UTC
Your net.pl missing bracket. It would be difficult for people to understand and help. By the way, I would suggest you to indent your code ;-) Update: A common situation for pipe close to fail is that, IO buffer is not flushed.	[reply]