shell script that check with wget of site is online every 2 seconds

[nickds123]

hello

Does anyone know how I can make a shell script that checks every 2 seconds of a site is online with wget?

[Irithori]

May I ask, what you intend to do?

For monitoring:
1) 2 seconds is a very low value.
Especially for a shell based solution.
You might run into scaling issues.
Imho, a 5min interval is suitable here.
2) define "online"
Is a 404 online? Probably not from a users point of view.
But for a (dumb) wget monitor: yes, it is online. The webserver answered.

For takeover:
Some HA/Loadbalancing solutions keep status of the pool members.
Non reacting members will then no longer get requests.

[nickds123]

1) 5 min is also good, it was a example
2) a 404 is not online (when de wget return nothing it is offline

[Irithori]

Ok, monitoring it is.

Then I would suggest to not reinvent the wheel and instead choose one of the well established solutions:
- Nagios
- Incinga
- Xymon
- Munin

There are others as well for about any scale and purpose.
Personally, I like xymon

[nickds123]

thx for your reply

I'm not really searching for a hole application but only a small bash/shell script that do a simply check just for testing.

I tried it but my script don't work

# !/usr/local/bin/bash

if wget -qO- SITE
then
echo "down"

else
echo "up"
exit
fi

[nixblog]

You could try this,

#!/bin/bash

if wget -q http://linuxforums.org
then
echo "up"

else
echo "down"
exit
fi

test it with a non-existent domain too such as drwwwww.org

[Irithori]

Nitpicker:
- Indentation improves readability
- This wget would download and save a index.html, then index.html.1, index.html.2.
So you would need something like -O- <URL> >/dev/null


But as I said earlier:
This is NOT a test: Website is up/down.
This is just a test: Webserver is running.

To check the website, one could use a URLs, that also need e.g. DBs or an internal search engine.
Then check the header for http return codes AND correct content.
Only then can one be fairly sure, that the site is operational.

Additonal hint:
It makes sense to run this check from at least a different machine, and best from an outside network.

[Irithori]

Additional nitpick
bash is not neccessarily in /bin

This shebang is better

#!/usr/bin/env bash

[nixblog]

Nitpicker:
- Indentation improves readability
- This wget would download and save a index.html, then index.html.1, index.html.2.
So you would need something like -O- <URL> >/dev/null

It's a few lines of code and no ones gonna get too confused eh, any particular style of indentation?

Yeah, redirect it to the garbage bin - i missed it out

But as I said earlier:
This is NOT a test: Website is up/down.
This is just a test: Webserver is running.

The poster seems to be after a simple "doe's it respond test" so lets keep it simple...

You would have to test an entire website content to make sure it was ok - even static pages, they could be compromised. If the poster wants simple, give him what he wants and let him explore if he needs to at a later date.

Additonal hint:
It makes sense to run this check from at least a different machine, and best from an outside network.

How about every machine on the net

Seriously, yes that's a good call.

[nixblog]

Additional nitpick
bash is not neccessarily in /bin

This shebang is better

#!/usr/bin/env bash

You could do away with the whole shebang entirely as it will still work but, not best practice I guess.