Writing from stdout to the browser?

Rails
1

hi all,

i’m working on a rails app that calls a ruby script which writes to
$stdout. i’d like somehow intercept that text and write it in realtime
(usuing ajax?) to the web browser. does anyone have general (or
specific)
hints about how to approach this?

i can’t change the code of the the called script, which is currently
called
using backticks.

thanks for any help!!

-reid

2

On 13 Mar 2008, at 01:31, Reid O. wrote:

hi all,

i’m working on a rails app that calls a ruby script which writes to
$stdout. i’d like somehow intercept that text and write it in
realtime (usuing ajax?) to the web browser. does anyone have
general (or specific) hints about how to approach this?

i can’t change the code of the the called script, which is currently
called using backticks.

Well say your script was

#!/usr/bin/env
puts “Hello world”

Then
output = ./test.rb
will set output to Hello world.

You’ll only get it when the program returns. If that’s not ok, then
you probably want to use IO.popen or similar and then read from the
pipe it yields you.

Fred

3

if i used the IO.popen method, what ajax technique could i use to get
the
browser to display the collected text as i gather it?

On Thu, Mar 13, 2008 at 4:38 AM, Frederick C. <

4

Reid O. wrote:

if i used the IO.popen method, what ajax technique could i use to get
the browser to display the collected text as i gather it?

An iframe may be the only way.

–
We develop, watch us RoR, in numbers too big to ignore.

5

ah yes. that’s what i want. this is my first project using AJAX, so i
have
a lot to learn.

the text i’ll be loading into the iframe is a log file that sometimes
grows
as quickly as 1 line per second and other times as slowly 1 line per
hour.
is there a way that the rails server can tell the browser when a new
line is
ready to be uploaded, instead of having to check back at regular
intervals?

On Mon, Mar 17, 2008 at 9:12 PM, Mark Reginald J.
[email protected]

6

Reid O. wrote:

ah yes. that’s what i want. this is my first project using AJAX, so i
have a lot to learn.

the text i’ll be loading into the iframe is a log file that sometimes
grows as quickly as 1 line per second and other times as slowly 1 line
per hour. is there a way that the rails server can tell the browser
when a new line is ready to be uploaded, instead of having to check back
at regular intervals?

An iframe would have allowed you to simply point the src parameter of
the iframe to the stream and let the browser render it progressively
as if it was a normal webpage. But unless there is some way to
keep the loading alive (e.g. sending null characters), I fear
that browsers will time-out at the 1 line/hour rate you want.

So you might have to go to a more complicated AJAX polling method.

Others may be able to suggest a good solution for your circumstances.

–
We develop, watch us RoR, in numbers too big to ignore.