PERL Beginners - two way piped open

Author

two way piped open

Bryan R Harris

2005-08-24, 6:56 pm

I'd like to open 2-way pipe to a tool that we have here. It's called
yprtool and once it's open, you give it 3 numbers to its STDIN and it spits
out 3 numbers to its STDOUT. It stays open until you ctrl-c it.

What's the correct syntax for opening something like this?

This doesn't work:

**************************************
$yprtool = '/Users/bh/Library/models/yprtool';
open(YPRTOOL, "+<$yprtool|") or die "open error blah";
print YPRTOOL "$a $b $c\n";
$return = <YPRTOOL>;
close(YPRTOOL) or die "a cruel death";
**************************************

I think the problem is in the "+<", but I'm not sure.

- B

Wiggins d'Anconia

2005-08-24, 6:56 pm

Bryan R Harris wrote:
>
> I'd like to open 2-way pipe to a tool that we have here. It's called
> yprtool and once it's open, you give it 3 numbers to its STDIN and it spits
> out 3 numbers to its STDOUT. It stays open until you ctrl-c it.
>
> What's the correct syntax for opening something like this?
>
> This doesn't work:
>
> **************************************
> $yprtool = '/Users/bh/Library/models/yprtool';
> open(YPRTOOL, "+<$yprtool|") or die "open error blah";
> print YPRTOOL "$a $b $c\n";
> $return = <YPRTOOL>;
> close(YPRTOOL) or die "a cruel death";
> **************************************
>
> I think the problem is in the "+<", but I'm not sure.
>
> - B
>

Check out the IPC::Open2 and IPC::Open3 modules, they are standard.

perldoc IPC::Open2
perldoc IPC::Open3

Additionally there is good information available in,

perldoc perlipc

http://danconia.org

Bryan R Harris

2005-08-24, 6:56 pm

That does it, thanks, Wiggins!

- B

> Bryan R Harris wrote:
>
> Check out the IPC::Open2 and IPC::Open3 modules, they are standard.
>
> perldoc IPC::Open2
> perldoc IPC::Open3
>
> Additionally there is good information available in,
>
> perldoc perlipc
>
> http://danconia.org

Bryan R Harris

2005-08-24, 6:56 pm

And a follow-on question:

Any idea why I have to send the yprtool two "\n"s instead of one to make it
work? With just one it hangs... On the command line, it definitely works
with just one.

**************************************
($y,$p,$r) = (split(' ', $lines[15]))[11..13];

use IPC::Open2;
local (*GETYPR, *SENDYPR);
$pid = open2(\*GETYPR, \*SENDYPR, "$yprtool -l 90 0 0 ");

print SENDYPR "$y $p $r\n\n";
($y2, $p2, $r2) = split(' ',<GETYPR> );

close GETYPR;
close SENDYPR;

print "y: $y, p: $p, r: $r\n";
print "y2: $y2, p2: $p2, r2: $r2\n";
**************************************

TIA.

- Bryan

> That does it, thanks, Wiggins!
>
> - B
>
>
>
>
>

Timothy Johnson

2005-08-24, 6:56 pm

Just a thought, but this behavior might be caused by Perl buffering your
output. =20

Try selecting your file handle and then setting $| to 1. That way Perl
should send your output immediately.

-----Original Message-----
From: Bryan R Harris [mailto:Bryan_R_Harris@raytheon.com]=20
Sent: Wednesday, August 24, 2005 1:51 PM
To: Beginners Perl
Subject: Re: two way piped open

And a follow-on question:

Any idea why I have to send the yprtool two "\n"s instead of one to make
it
work? With just one it hangs... On the command line, it definitely
works
with just one.

<snip>

Bryan R Harris

2005-08-24, 6:56 pm

Makes sense, but that's not it, unfortunately. I tried it and it still
hangs...

Also, strangely, with the two "\n"s, the next time I try to write to the
filehandle it says the pipe is broken.

Here's sample output from the tool:

**************************************
ralph 2104% yprtool -l 90 0 0
50 50 50 <- I type this
130.000000 -50.000000 -130.000000 <- it outputs this
40 40 40 <- I type this
140.000000 -40.000000 -140.000000 <- it outputs this
<- I type a return

ERROR: Wrong number of inputs in stream. <- and it complains

Throwing exception (1: "1") at ../src/YprTool.cpp line 192.
Program error...exiting
**************************************

- B

>
> Just a thought, but this behavior might be caused by Perl buffering your
> output.
>
> Try selecting your file handle and then setting $| to 1. That way Perl
> should send your output immediately.
>
>
>
>
> -----Original Message-----
> From: Bryan R Harris [mailto:Bryan_R_Harris@raytheon.com]
> Sent: Wednesday, August 24, 2005 1:51 PM
> To: Beginners Perl
> Subject: Re: two way piped open
>
>
>
> And a follow-on question:
>
> Any idea why I have to send the yprtool two "\n"s instead of one to make
> it
> work? With just one it hangs... On the command line, it definitely
> works
> with just one.
>
> <snip>
>
>

Bryan R Harris

2005-08-24, 6:56 pm

Figured it out, Timothy had the right idea. The tool was buffering its
output!

- B

> Makes sense, but that's not it, unfortunately. I tried it and it still
> hangs...
>
> Also, strangely, with the two "\n"s, the next time I try to write to the
> filehandle it says the pipe is broken.
>
> Here's sample output from the tool:
>
> **************************************
> ralph 2104% yprtool -l 90 0 0
> 50 50 50 <- I type this
> 130.000000 -50.000000 -130.000000 <- it outputs this
> 40 40 40 <- I type this
> 140.000000 -40.000000 -140.000000 <- it outputs this
> <- I type a return
>
> ERROR: Wrong number of inputs in stream. <- and it complains
>
> Throwing exception (1: "1") at ../src/YprTool.cpp line 192.
> Program error...exiting
> **************************************
>
> - B
>
>
>
>
>
>
>

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