running external process?

[Ferenc Engard]

Hi all,

Is there a simple way to spawn an external program, feed its stdin, and
get its stdout?

The problem with popen is, if I want to feed a few MB's of input to it,
then it hangs (I suspect that its stdout IO buffer is full) before I
could read out its stdout on the next line. So, the following do not
work:

io=IO.popen("externalfilter")
io.write(verybigstring)
result=io.read

Thanks,
Ferenc

 

[Wesley J Landaker]

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Hi all,

Is there a simple way to spawn an external program, feed its stdin,
and get its stdout?

The problem with popen is, if I want to feed a few MB's of input to
it, then it hangs (I suspect that its stdout IO buffer is full)
before I could read out its stdout on the next line. So, the
following do not work:

io=3DIO.popen("externalfilter")
io.write(verybigstring)
result=3Dio.read

require 'open3'
Open3.popen3("externalfilter") { |sin,sout,serr|
sin.write(verybigstring)
result =3D sout.read
}

=2D-=20
Wesley J. Landaker - (e-mail address removed)
OpenPGP FP: 4135 2A3B 4726 ACC5 9094 0097 F0A9 8A4C 4CD6 E3D2


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[Ara.T.Howard]

Date: Sun, 18 Jan 2004 21:39:41 +0900
From: Ferenc Engard <[email protected]>
Newsgroups: comp.lang.ruby
Subject: running external process?

Hi all,

Is there a simple way to spawn an external program, feed its stdin, and
get its stdout?

The problem with popen is, if I want to feed a few MB's of input to it,
then it hangs (I suspect that its stdout IO buffer is full) before I
could read out its stdout on the next line. So, the following do not
work:

io=IO.popen("externalfilter")
io.write(verybigstring)

io.close # the program is still reading it's stding here

result=io.read

Thanks,
Ferenc

-a
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[Wesley J Landaker]

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require 'open3'
Open3.popen3("externalfilter") { |sin,sout,serr|
sin.write(verybigstring)
result =3D sout.read
}

Or (should have mentioned this in my first e-mail) if that still hangs,=20
you might try using Threads:

require 'open3'
Open3.popen3("externalfilter") { |sin,sout,serr|
threads =3D []
threads << Thread.new {
sin.write(verybigstring)
}
threads << Thread.new {
result =3D sout.read
}
threads.each {|t| t.join }
}

=2D-=20
Wesley J. Landaker - (e-mail address removed)
OpenPGP FP: 4135 2A3B 4726 ACC5 9094 0097 F0A9 8A4C 4CD6 E3D2


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[Robert Klemme]

Hi all,

Is there a simple way to spawn an external program, feed its stdin, and
get its stdout?

The problem with popen is, if I want to feed a few MB's of input to it,
then it hangs (I suspect that its stdout IO buffer is full) before I
could read out its stdout on the next line. So, the following do not
work:

io=IO.popen("externalfilter")
io.write(verybigstring)
result=io.read

You need at least two threads or non blocking IO. How about:

IO.popen( "cat", "w+" ) do |io|
r = Thread.new(io) do |reader|
while ( line = reader.gets )
line.chomp!
$stdout.puts line
end
end

(1..100000).each {|i| io.puts i}
r.join
end

Regards

robert

 

[Ferenc Engard]

The problem with popen is, if I want to feed a few MB's of input to it,

You need at least two threads or non blocking IO. How about:

IO.popen( "cat", "w+" ) do |io|
r = Thread.new(io) do |reader|
while ( line = reader.gets )
line.chomp!
$stdout.puts line
end
end

(1..100000).each {|i| io.puts i}
r.join
end

Thank you, this is what I need. Since I program in ruby, a 8-9 rows of
code seems too difficult to write by myself. :-/

Ferenc