Im trying to do a loop in ruby that display a number + 1 every second. Id like the user to be able to input when he want. the problem is that i have to input something for the loop to continue. sorry for my bad english im fr
p.s im using a online compiler (repl.it)
You can accomplish what you want using threads and some simple state variables to communicate between the threads.
In this example we use a variable #stop to signal from the main thread to the counting thread when it's time to end the counting loop.
This example works on repl.it directly:
https://repl.it/repls/RingedIlliterateEnglishsetter
Hopefully this gives you some ideas on how to proceed.
#stop = false
thr = Thread.new {
puts "Counting thread starting..."
i = 0
loop {
i += 1
puts i
sleep 1
break if #stop
}
puts "Counting thread exit..."
}
loop {
puts "\nWaiting for input...\nType 'stop' to exit..."
input = gets.chomp
if input == "stop"
puts "Stopping..."
#stop = true
break
end
}
# Wait for counting thread to end
thr.join
puts "Main program exit..."
Related
I have the following:
text_counter = 0
MAXTEXT_COUNTER = 10
puts "hello, this will start"
loop do
puts "hello"
text_counter += 1
sleep(2)
if text_counter >= MAXTEXT_COUNTER
break
end
end
sleep(7200)
print "ended test"
Once the break has happened, how can I get it to start again from the top?
I'm now thinking I could nest this loop in an until loop with the condition of text_counter == 1000. This would break, then sleep for 2 hours, then start again until it hits 1000.
It looks like you need a loop within a loop where you repeat one N times, the other M times:
MAXTEXT_COUNTER = 10
puts "hello, this will start"
loop do
MAXTEXT_COUNTER.times do
puts "hello"
sleep(2)
end
print "ended test"
sleep(7200)
end
The outer loop is perpetual. The inner one runs a certain number of times and stops using the times method.
You're looking for next
It functions similarly to break, but returns control back to the top of the loop. It's great for creating flat control flow.
For example
0.upto(100) do |i|
if i % 7 == 0
puts "#{i} is a multiple of 7"
next
end
puts i
end
There is a retry keyword which repeats the loop from top, just what you've asked.
Or you can wrap your loop into a method and continuously call that method.
Basically in my search for code which will loop, and terminate upon user input, i managed to find code here, and after some alteration, produced this:
#desired destination method, however loop persists!!
def desired_method
print "method entered"
end
Thread.new do
while line = STDIN.gets
break if line.chomp == "" # code detects user input
end
desired_method
end
# program will loop here until user presses enter
loop do
puts "foo"
sleep 1
end
This code is brilliant, and will enter the method 'desired_method' when i hit enter, however the loop persists!! printing 'foo' perpetually after "method entered"!!. I have done some research prior to posting this question on how to kill threads, which i believe may hold the answer. My attempts included naming the thread and using the 'thread.exit' function to kill it, however these techniques have remained unsuccessful.
Can anyone illustrate how i might enter the 'desired_method' method without the persisting "foo" print?
Thanks in advance, and greatly appreciated.
An easy solution here is to use semaphore, signalling between threads with a variable access to both places:
# This will be out stop flag, for signalling between threads.
#time_to_stop = false
def desired_method
print "method entered"
# Here we want the loop in the other thread to stop.
#time_to_stop = true
end
Thread.new do
while line = STDIN.gets
break if line.chomp == "" # code detects user input
end
desired_method
end
# program will loop here until user presses enter
loop do
puts "foo"
sleep 1
# only continue if the stop flag is not set.
break if #time_to_stop
end
Hope this helps.
Why does this code work (I see the output 1 2 3):
for i in 1..3
Thread.new{
puts i
}
end
However, the following code does not produce the same output (I do not see the output 1 2 3)?
for i in 1..3
Thread.new{
sleep(5)
puts i
}
end
When you hit the end of the script, Ruby exits. If you add sleep 10 after the final loop, you can see the output show up. (Albeit, as 3 each time, because the binding to i reflects the value at the end of processing, and the sleep causes a thread switch back to the loop.)
You might want something like:
threads = []
for i in 1..3
threads << Thread.new {
sleep 5
puts i
}
end
threads.map {|t| t.join }
That will wait for all the threads to terminate before exiting.
I'm trying to find a way to terminate a loop when the user hits 'x'+Enter. I want the loop to just keep running in the background until the user cancels it.
Something along these lines:
while gets.chomp != 'x'
puts 'looping...'
sleep 1
end
I'm a beginner with programming and have searched far and wide for how to do this so any help would be deeply appreciated.
You have to use threads for this:
Thread.new do
while line = STDIN.gets
break if line.chomp == 'x'
end
exit
end
# whatever you want to do in the background
# (or rather in the foreground, actually)
loop do
puts "foo"
sleep 1
end
The problem is that STDIN.gets blocks, so you can't do something else at the same time without parallelizing the program by using a background thread that only checks for input.
I have a while loop consistently listening to incoming connections and outputting them to console. I would like to be able to issue commands via the console without affecting the output. I've tried:
Thread.new do
while true
input = gets.chomp
puts "So I herd u sed, \"#{input}\"."
#Commands would be in this scope
end
end
However, that seems to pause my entire script until input is received; and even then, some threads I have initiated before this one don't seem to execute. I've tried looking at TCPSocket's select() method to no avail.
Not sure where are the commands you want to "continue running" in your example. Try this small script:
Thread.new do
loop do
s = gets.chomp
puts "You entered #{s}"
exit if s == 'end'
end
end
i = 0
loop do
puts "And the script is still running (#{i})..."
i += 1
sleep 1
end
Reading from STDIN is done in a separate thread, while the main script continues to work.
Ruby uses green threads, so blocking system calls will block all threads anyway. An idea:
require 'io/wait'
while true
if $stdin.ready?
line = $stdin.readline.strip
p "line from stdin: #{line}"
end
p "really, I am working here"
sleep 0.1
end