Please explain this "if" in C language

Question

I'm coming back to 'C' after few years. I searched the net for how to use Twitter API in C and I came across this question on stackoverflow.

Question: Accessing the Twitter Streaming API with C

I can't understand the "if" in this code:

if(curl) {

I can't understand it, what does it do? What is it's function? Shouldn't there be some conditional?

Please help. Thanks

`curl` is the condition. If it's not `None`, it evaluates to 'truehood'. — OJFord, Aug 17 '14 at 17:52
In C, if a variable resolves to zero, it evaluates to false. If it is non-zero, it evaluates to true. That if tests if the variable named "curl" evaluates to true or false. — DwB, Aug 17 '14 at 17:52
@gipi I know if in C but I never encountered this type of if — want2code, Aug 17 '14 at 18:01

score 0 · Accepted Answer · answered Aug 17 '14 at 17:52

0

It checks to see if the pointer curl is not null (a null pointer is equivalent to the value 0, which is false when considered as a Boolean).

answered Aug 17 '14 at 17:52

Blair Conrad

233,004
25
132
111

score 0 · Answer 2 · answered Aug 17 '14 at 17:53

0

You should have looked at the previous three lines,

CURL *curl;
CURLcode res;

curl = curl_easy_init();
if(curl) {

In the above code, did curl_easy_init() succeed in initialization.

answered Aug 17 '14 at 17:53

Elliott Frisch

198,278
20
158
249

score 0 · Answer 3 · answered Oct 23 '17 at 06:44

In C language, there are no actual booleans. But 0 and 1 can be treated as booleans in C language.. where 0 is false and anything nonzero is true including negative numbers. So this curl is a pointer and is assigned zero if not initialized. Hence it checks if curl is initialized and if it is.. if block gets executed

Please explain this "if" in C language

3 Answers3