Im trying to do a script that if a host is up, it needs to run code

Would:

Work?

so what do you think? Does it work as expected? Did you try it already?

http://www.tldp.org/LDP/abs/html/exit-status.html
http://bencane.com/2014/09/02/unders...-bash-scripts/
http://stackoverflow.com/questions/5...ds-efficiently

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Thats why Im asking before adding it to the code.

Your assignment to check is missing quotes, and you are not executing anything in the if.

pan64's point is that you should run that fragment. You do not need to add it to any code, you can run that script fragment as is, by adding a shebang at the top and putting that portion into a temporary script file, debug it and find out if it runs. Per smallpond's comment, you need to properly quote the ping command when you assign the result to a variable, give this a read about some ways to assign the output of a bash command to a variable.

A further suggestion is that you check the manual page for ping(8) where it talks about what ping returns on error. I do believe you are using it correctly, however I always do prefer to double check.

A final suggestion is to put "set -xv" at the top of that script, along with the shebang at the top of the script. Yes I realize you were saying that this is a code fragment, however we recommend that you test just this fragment to validate that you have this section correct.

you're not passing to $check what you think you are passing to $check, thus why you need to read the links pan64 linked. So to answer the question, no it would not work.

Try this:
Enjoy the Goodness.
Be certain to look for Conditional Expressions in the topic links pan64 gave us.

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Notes.

Might consider a different connection method. Ping may be blocked while tcp connections still work. More and more ping is becoming a poor network tool.

ping and traceroute are good debugging tools; only paranoid or masochistic persons block ICMP.
Even shorter is
The code after then is run if the code between if and then has exit status zero(success).

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Switches block ping when under loads by design.

ping is unreliable as a test.

Well perhaps the suggestion therefore would be to try multiple contact techniques and have a few if-else tests, once one of them succeeds, then the host is deemed available.

I'm also assuming that their script once it deems a host to be available, tries to contact it using some other protocol. Therefore a test for verification that the next command succeeds would be in order. I tend to code defensively and check return status for all that I can verify.

Not sure this needs to iterate as a discussion over whether or not to use ping. The coder may know their network or their situation and feel that ping is perfectly acceptable, and may always have been. They may be pinging an internal network address, they may be pinging something which is on a purely private network. As an example, chassis based systems for Telco which I've worked on years ago, had internal networks which were 10.x.x.x and they were internal to the chassis. Finding another card meant engaging it using some form of network protocol, one of which could be ping.

Be careful that you are not re-inventing Nagios, the hard way . . .

(Nagios is a corporation with a number of products, but "Nagios Core" is free.)