Hi,
is it possible to get a continuous output stream with IO.popen('xxx')
example,
IO.popen('tail -f some_log_file')...
where the goal is to see the tail output as it's generating, rather than waiting for the process to complete to dump the generated output.
Thank You,
Andy Koch
I know this is possible with EventMachine's version of popen. If no one else
comes up with a standard way to do it, look at EventMachine.
On 7/19/07, Andy Koch <andy.koch@pc-doctor.com> wrote:
Hi,
is it possible to get a continuous output stream with IO.popen('xxx')
example,
IO.popen('tail -f some_log_file')...
where the goal is to see the tail output as it's generating, rather than
waiting for the process to complete to dump the generated output.
Andy Koch wrote:
Hi,
is it possible to get a continuous output stream with IO.popen('xxx')
example,
IO.popen('tail -f some_log_file')...
where the goal is to see the tail output as it's generating, rather than
waiting for the process to complete to dump the generated output.
That *is* what you get with IO.popen.
For example,
IO.popen('tail -f testfile').each_line do |line|
puts line.upcase
end
prints out the upcased version of any line added to testfile as soon as it is
added to the file.
--
Ist so, weil ist so
Bleibt so, weil war so
Sebastian Hungerecker wrote:
That *is* what you get with IO.popen.
For example,
IO.popen('tail -f testfile').each_line do |line|
puts line.upcase
end
prints out the upcased version of any line added to testfile as soon as it is
added to the file.
I was just wondering about this, and I see that you are correct, *usually*--this is very strange.
file1:
#!/usr/bin/env ruby
5.times {puts "hi"; sleep 0.5}
file2:
#!/usr/bin/env ruby
IO.popen("./file1").each_line { |line| puts line }
When running file2 (which should stream the output from file1), the output is not streamed, but instead saved up until "file1" finishes running and then dumped. Note that this only occurs when file1 is a ruby file--replacing it with a bash script that does the same thing causes the output to stream properly. I am perplexed. Any insight? (Is this a bug?)
I'm using ruby 1.8.5 on linux.
Dan
Dan Zwell wrote:
Sebastian Hungerecker wrote:
That *is* what you get with IO.popen.
For example,
IO.popen('tail -f testfile').each_line do |line|
puts line.upcase
end
prints out the upcased version of any line added to testfile as soon as it is
added to the file.I was just wondering about this, and I see that you are correct, *usually*--this is very strange.
file1:
#!/usr/bin/env ruby
5.times {puts "hi"; sleep 0.5}file2:
#!/usr/bin/env ruby
IO.popen("./file1").each_line { |line| puts line }When running file2 (which should stream the output from file1), the output is not streamed, but instead saved up until "file1" finishes running and then dumped. Note that this only occurs when file1 is a ruby file--replacing it with a bash script that does the same thing causes the output to stream properly. I am perplexed. Any insight? (Is this a bug?)
I'm using ruby 1.8.5 on linux.
Dan
I've made this a bit more accessible for the non-linux folks:
In IRB, try running thes one-liner (with wide margins):
IO.popen("ruby -e '5.times {|n| puts n; sleep 1}'").each_line {|line| puts line}
It should print a number every second, right? Well, it doesn't for me...
Dan
Dan Zwell wrote:
file1:
#!/usr/bin/env ruby
5.times {puts "hi"; sleep 0.5}file2:
#!/usr/bin/env ruby
IO.popen("./file1").each_line { |line| puts line }When running file2 (which should stream the output from file1), the
output is not streamed, but instead saved up until "file1" finishes
running and then dumped.
That seems to be a buffering issue. If you set STDOUT.sync to true in file1,
it will work as expected.
--
NP: Explosions in the Sky - Welcome, Ghosts
Ist so, weil ist so
Bleibt so, weil war so
Sebastian Hungerecker wrote:
Dan Zwell wrote:
file1:
#!/usr/bin/env ruby
5.times {puts "hi"; sleep 0.5}file2:
#!/usr/bin/env ruby
IO.popen("./file1").each_line { |line| puts line }When running file2 (which should stream the output from file1), the
output is not streamed, but instead saved up until "file1" finishes
running and then dumped.That seems to be a buffering issue. If you set STDOUT.sync to true in file1,
it will work as expected.
Thanks, that's good to know. Having this behavior unexplained made me a bit nervous about using IO.popen.