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If statement to compare two strings

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# 1  
Old 06-20-2017
If statement to compare two strings
Hi,

I am trying to do the following to see if "ip" is already present in a file.

Code:
if ["$ip" == "(cat /etc/hosts.deny | grep {$ip})"]; then
		echo "hi"
	else
		 echo "hello"
	fi

I am seeing errors on the if statement. Can someone please correct the syntax for me? Thanks
Last edited by Scrutinizer; 06-20-2017 at 12:45 AM.. Reason: code tags
# 2  
Old 06-20-2017
Quote:
Originally Posted by waince
Hi,

I am trying to do the following to see if "ip" is already present in a file.

Code:
if ["$ip" == "(cat /etc/hosts.deny | grep {$ip})"]; then
		echo "hi"
	else
		 echo "hello"
	fi

I am seeing errors on the if statement. Can someone please correct the syntax for me? Thanks
Try the following:
Code:
if grep -q "$ip" /etc/hosts.deny; then
    echo "hi"
else
    echo "hello"
fi

or

Code:
grep -q "$ip" /etc/hosts.deny && echo "hi" || echo "hello"

---------- Post updated at 08:31 PM ---------- Previous update was at 08:14 PM ----------

By the way, the errors most likely are because it needs spaces between [ and ]
Nevertheless, you are saying something you do not intend to.

The value stored in the variable ip is equal to the literal string formed with the characters (cat /etc/hosts.deny | grep {[*]value in ip variable})
Very unlikely.

[*] the ip variable will be expanded and its content will show instead.
# 3  
Old 06-20-2017
A few comments on top of what Aia already said
- unless hosts.deny contains EXACTLY ONE line consisting only of that $ip contents, the test will fail
- you need to deploy "command substitution" $(...) (c.f. man bash)
- the test can be phrased way simpler and safer or even omitted (see Aia's proposal)
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