Re: Attn: Robert (Non-Blocking Support Revisited)
One of the main reasons for wanting non-blocking support is
so a program can access a URL and not get stuck waiting for the
download to occur (or time-out).
The Linux/FreeBSD distribution has this "news.exu" multitasking
demo, which also runs on Windows, provided you have wget.exe
in the current directory, or on your PATH.
In the next release I'll include it in the Windows installation as well.
This might be useful for some people, until we have something better.
-- news.exu: Search news pages
-- All this demo does is read several Web pages in parallel
-- and report on the number of occurences of a word or phrase.
-- Each page is handled by a separate Euphoria task running
-- in parallel with several other tasks.
-- usage:
-- exw news.exu string
-- or:
-- exw news.exu "a multi-word phrase"
-- (case insensitive search)
-- On Linux/FreeBSD use exu instead of exw.
-- This demo uses Euphoria's new multitasking feature. It can run
-- on Linux, FreeBSD, or Windows, without change.
-- It creates multiple wget background processes, each retrieving one Web page.
-- You can get a version of wget for Windows from:
-- http://www.gnu.org/software/wget/wget.html
-- Linux and FreeBSD systems will probably already have it.
-- A Euphoria task is assigned to each instance of wget, searching the
-- Web page text as it arrives. In this way, when a task is blocked due
-- to a delayed response from a particular server, the program can easily
-- switch to another task that is not blocked. The program quits after a
-- period of 10-15 seconds with no progress made on any page.
include wildcard.e
include graphics.e
sequence cl
sequence search_phrase
cl = command_line()
if length(cl) >= 3 then
search_phrase = cl[3]
else
puts(1, "Usage:\n")
puts(1, " exw news search-phrase\n")
if getc(0) then
end if
abort(1)
end if
-- news sources
sequence URLs
URLs = {
"http://www.cbc.ca/news/",
"http://www.juancole.com/",
"http://www.abc.net.au/",
"http://abcnews.go.com/",
"http://english.aljazeera.net/HomePage",
"http://news.bbc.co.uk/",
"http://www.cbsnews.com/",
"http://cnn.com/",
"http://www.democracynow.org/index.pl",
"http://www.foxnews.com/",
"http://www.guardian.co.uk/",
"http://www.msnbc.msn.com/",
"http://www.reuters.com/",
"http://www.whatreallyhappened.com/",
"http://news.yahoo.com/"
}
sequence null_device, del_cmd
if platform() = LINUX then
URLs = URLs[1..9] -- less room on screen
null_device = "/dev/null"
del_cmd = "rm"
else
null_device = "NUL"
del_cmd = "del"
end if
integer progress, quit
procedure search_url(sequence url, sequence string)
-- download a Web page and search it for a string
integer f, hits
integer line_count
object line
sequence mytemp, ustring
if task_self() > 20 or task_self() < 0 then
printf(1, "\n1. my task id is rubbish: %g\n", task_self())
if getc(0) then
end if
abort(0)
end if
position(task_self()*2+1, 1)
printf(1, "task %2.0f: %s\n waiting for wget...", {task_self(),
url})
ustring = upper(string)
hits = 0
-- run a copy of wget as a background process
mytemp = sprintf("newstemp%.0f.html", task_self())
system(sprintf("wget -q -b -O %s %s > %s", {mytemp, url, null_device}), 2)
f = -1
while f = -1 do
-- wait until file exists
if quit then
return
end if
if task_self() > 20 or task_self() < 0 then
printf(1, "\n2. my task id is rubbish: %.0f\n", task_self())
if getc(0) then
end if
abort(0)
end if
task_schedule(task_self(), {1.0, 2.0})
task_yield()
f = open(mytemp, "rb")
end while
position(task_self()*2+2, 1)
text_color(BRIGHT_RED)
puts(1, " waiting for data...")
text_color(WHITE)
line_count = 0
while 1 do
line = gets(f)
if atom(line) then
-- could be actual end-of-file, or maybe there's more coming
task_schedule(task_self(), {1.0, 1.5})
while 1 do
line = gets(f)
if sequence(line) then
exit -- more data came in
end if
if quit then
return -- we've been told to quit
end if
task_yield()
end while
end if
if match(ustring, upper(line)) then
hits += 1
end if
line_count += 1
position(task_self()*2+2, 1)
text_color(BRIGHT_GREEN)
printf(1, " matched %d lines out of %d ", {hits, line_count})
text_color(WHITE)
progress = 1
-- this yield is not necessary, but it
-- lets you see the parallelism better
task_schedule(task_self(), 1)
task_yield()
end while
end procedure
integer t
for i = 1 to length(URLs) do
t = task_create(routine_id("search_url"), {URLs[i], search_phrase})
task_schedule(t, 1)
end for
system(del_cmd & " newstemp*.html > " & null_device, 2)
clear_screen()
if text_rows(43) then
end if
puts(1, "Looking for lines containing \"" & search_phrase & "\"")
atom time_out
time_out = time() + 45
task_schedule(0, {2.5, 3.0}) -- check the time every 2.5 to 3.0 seconds
quit = 0
while 1 do
progress = 0
task_yield()
if progress then
-- quit 10 seconds after no more lines are read
-- from any file by any task
time_out = time() + 10
else
if time() > time_out then
exit
end if
end if
end while
quit = 1 -- signal all tasks to report any final results and terminate
while length(task_list()) > 1 do
task_yield()
end while
position(2*length(URLs)+3, 1)
puts(1, "\nAll Done.\n")
if getc(0) then
end if
system(del_cmd & " wget-log* > " & null_device, 2)
Regards,
Rob Craig
Rapid Deployment Software
http://www.RapidEuphoria.com
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