Using popen


#1

Hi, all.

look this code.


require ‘open3’
include Open3

stdin, stdout, stderr = popen3(“ls”)

puts stdout.sysread(1024)

this code shows up a file list normally.

but, THIS CODE


require ‘open3’
include Open3

stdin, stdout, stderr = popen3(“ftp ftp.gnu.org”)

puts stdout.sysread(1024)

looks like a hang.

Could you tell me why this thing is happened?


#2

Jun Y. Kim wrote:


require ‘open3’
include Open3

stdin, stdout, stderr = popen3(“ftp ftp.gnu.org”)

puts stdout.sysread(1024)

looks like a hang.

Could you tell me why this thing is happened?

Probably because (a) the ftp client is waiting for data from the
terminal before it has sent 1024 bytes of reply, and/or (b) the ftp
client expects to be run on an interactive tty.

If (b) applies, look at using require ‘pty’

But for FTP, you are almost certainly better off using Net::FTP from the
Ruby standard library, rather than spawning an external ftp client.


#3

yes, ftp client is waiting some letters for log-in.

but, before that, client program print out “hello message” like


Connected to ftp.gnu.org.
220 GNU FTP server ready.
Name (ftp.gnu.org:junyoung):

under a hanging situation, I cannot also see this message.

anyway.
(a) I tried to get 1byte by sysread. it’s not different.
(b) Is interactive tty different from stdin, stdout?
I believe although ftp is using tty, it should print out something in
stdout.

    1. 15, ¿ÀÈÄ 10:01, Brian C. ÀÛ¼º:

#4

2009ë…„ 4ì›” 16일 (목) ì˜¤ì „ 9:59, Jun Y. Kim removed_email_address@domain.invalid님의 말:

under a hanging situation, I cannot also see this message.

anyway.
(a) I tried to get 1byte by sysread. it’s not different.
(b) Is interactive tty different from stdin, stdout?
I believe although ftp is using tty, it should print out something in
stdout.

Try this:
require ‘open3’
include Open3

stdin, stdout, stderr = popen3(“ftp -inv ftp.gnu.org”)
while line=stdout.gets
print line
end

I guess ftp is trying to interact with tty.
Using pty and expect is more suitable in this case

require ‘pty’
require ‘expect’

PTY.spawn(‘ftp ftp.gnu.org’) do |r,w,cid|
r.expect /Name.*:\s+/ do |line|
print line
w.puts “anonymous”
end
while line=r.gets
print line
end
end

Regards,

Park H.