Crontab Tutorial - VPS with AWS EC2 and Python Intro to AWS

Key Takeaways

hey guys welcome to your fourth AWS or really just any VPS web server tutorial where we left off showing you guys how to do you know run some of your Python scripts but now what I want to do is show you the cron tab and then probably in the coming videos show you how to run those Python scripts 1 run them run them simultaneously in the background and then also finally run them without hanging up when you log out your user so with that let's go ahead and get started the first thing we want to show you is the crontab the idea of the crontab is to run scheduled jobs it's or you call it most people call them cron jobs right so we're gonna go into the cron tab again you can get in there either with just a simple crontab dashi and you can use the default editor or you can just change or specify that your editor you want is Nano and we want to enter the crontab with the intention to edit it so here's our Kuran tab it's totally empty so how do we even set up a cron which pran will be on each line for one and to set up a cron the default is just five asterisks separated by a space and each asterisk has a meaning to it so this first star represents minutes so you can give it a value of 0 to 59 the second star represents hours again 0 to 23 the next star represents the day of the month so 1 to 31 the next star is gonna represent the actual month and this is gonna be a 1 to a 12 don't confuse that with a 0 2 and 11 because the other ones were giving us zero ideas subsequently you then have day of the week so this is going to be again a 0 to a 6 so kind of confusing the way they force you to do that but that's how it's done now the next thing is like say ok this is our minute so if we say and then you basically put your parameter on the other side of it right so let's say you wanted to run everything at the half hour you would just do this you would put it you've got the star there and the 30 right and I'm not quite sure I guess this because I got highlighted anyway star 30 that will run this cron that doesn't there's no nothing those specifications here but that would run this every happen every hour at the 30 so this will run every hour at the 30 minutes after the hour right if you wanted to run a cron every 30 minutes it would do a slash 30 and that will run it every 30 minutes conversely you could do something like this and run the cron every three minutes or if you did this it would run the cron at every third minute after the hour so let's say we want to leave it as every every one minute we wanted to run this cron same thing goes for all of these so like if you wanted to run a cron at one every day that's how you would do it subsequently if you wanted to run it every one hours you would do it this way although this full cron is really every one hour in one minute the Quran will run now in our case since we're mostly interested in doing Python scripts you're going to want to perceive this the script with what you want to run it with and you can either do it this way like user boom and Python writes s pythons location here but you can cut you can always treat these things at least for my phone you can always treat them just like it's at the line itself so you can most likely call Python and then the script so we could say example dot PI right and it will run this script at every one minute in one hour now I'm gonna go over here and actually will probably come in here and redo it since this file doesn't exist we'll go ahead and create the file it'll be the first thing we do so I'm gonna go ahead and exit out of here and I'm just going to say no to not save the changes so not CD back a couple of directories and let's make sure we're there and now we want to see the Ben and if we list out everything that's in let's see no so CP LS what we really wanted was first user yeah so CD in the user or USR I'm not sure that stands for user but that's what I say and then CD in the bin LS and now you should see here's where python is and you even got Python 26 and 2.6 and all that so anyway see the back out again see the home slash I think we're ec2 - user right I'm user okay so we have nothing here so let's go ahead and make our example of Python file so let's go nan-oh I guess we'll do running one dot pi first and we're gonna go ahead and import time and then we're gonna make our function and this is just going to be three tests one and it's gonna sleep for one second then it's gonna go ahead and call that function exit save yes good now I want to make a second version of this file so I can show you guys like simultaneous running so we've either a redo this or we can use a function that I didn't teach you guys yet and that's the copy so to copy something you do CP what do you want to copy well we want to copy running one dot pi and then what do you want to copy it to in this case I want to copy it to running to dot pot right so you do that it's copied we can LS and we can see okay yeah we've got gum both running at the moment now just for kicks I want to see if I can do you surf and python running one pi yeah okay so so you should be able to and we should probably make these loop as well anyway so you can either put out the full path like this will accept the full path where I or you could just straight say Python and that's for that for that cron so you can give the pole path like sometimes you might need to but yeah you can usually treat that crime it's it's like it's it's like you're using that user so each user is going to have his own little crontab right so as long as he's got the permissions to run it'll run just like it's he's typing in the line anyway I guess what we'll do is we'll quickly edit these these files here at least running one and we're going to just throw this in a Wow true loop here shift that over XE yes oh and I don't think it yeah we put the sleeper in the function so now when we go python running one time it's gonna run that script but if you'll see the only way we like if we tried any as hard as we could Python there actually was sorry I want to do yeah Python running to dot hi you just can't get it in there right so you'd have to click you know keyboard interrupt of the script and then you would have to call python running to dot pi and that's all fine and dandy you know we need to make python run into nano running to we want to have this one say test too so we can identify what's running okay so anyway so that was just the crontab basics we made these two files that we want want to run simultaneously and we see that we're having quite the hard time doing it so the next video I'm gonna be showing you guys how you can get them to actually run simultaneously so anyway stay tuned for that video as always thanks for watching thanks for the support in the subscriptions and until next time