For loop and confition including Curl command - bash

Question

I am trying to write a script where I enumerate users by checking the HTTP reponse length. I want to get output "good" when response is not equal 23, however I get these errors now:
for ((i=113;i<=115;i++)); do
if [[curl -i -s -k -X 'GET' "http://myurl/some.asp?q=$i" |
grep Content-Length | cut -d' ' -f2 != 23]]
then
echo "good"
fi
done
Output:
bash: [[curl: command not found
cut: !=: No such file or directory
cut: 23]]: No such file or directory
cut: !=: No such file or directory
cut: 23]]: No such file or directory
bash: [[curl: command not found
cut: !=: No such file or directory
cut: 23]]: No such file or directory
bash: [[curl: command not found
If I simply make a script without if condition, then it works well:
for ((i=113;i<=115;i++)); do
curl -i -s -k -X 'GET' "http://myurl/some.asp?q=$i" |
grep Content-Length
done
I checked many examples but can't seem to figure out where I am doing wrong.

Answer 1

After updating your initial error, you may have a syntax like (suggestion: put some effort on format, so that it is more clear what you have and what may be wrong):
for ((i=113;i<=115;i++))
do
if [[ curl -i -s -k -X 'GET' "http://myurl/some.asp?q=$i" | grep Content-Length | cut -d' ' -f2 != 23 ]]
then
echo "good"
fi
done
This is returning you the error:
bash: conditional binary operator expected bash: syntax error near
-i'`
Which is normal, because you are basically saying:
if [[ command ]]; then ...
Where command is a set of multiple piped commands. However, in [[ you just can add expressions on the form "$var" -eq 23 or "$(command)" -ne 23.
So use $( ) to execute the command: if [[ "$(command)" -ne 23 ]]:
if [[ "$(curl -i -s -k -X 'GET' "http://myurl/some.asp?q=$i" | grep Content-Length | cut -d' ' -f2)" -ne 23 ]]
Note I am using -ne to perform an integer comparison that means "not equal to".
Finally, notice that awk alone can do what grep and cut do in two steps:
... | grep "Content-Length" | cut -d' ' -f2
This means: check the line containing "Content-Length" and print its second field. awk makes it simple by saying:
... | awk '/Content-Length/ {print $2}'
And last, but not least, your expression for ((i=113;i<=115;i++)) can be also written as for i in {113..115} using brace expansion.

Answer 2

If you want to test a result of the command execution you should put it into $() . So the resulting script should look as follows:
for i in {113..115}; do if [[ $(curl -i -s -k -X 'GET' "http://myurl/some.asp?q=$i" | grep Content-Length | cut -d' ' -f2) != 23 ]]; then echo "good" ; fi; done
Also I've changed a way you iterate the values. {a..b} in bash provides a sequence from 'a' to 'b'.