why are these two strings not equal in c

Question

hey guys ok i wrote this code which would check if a get request is proper but at the last comparison it doesn't give me the expected result thank you in advance the problem is in the last if statement it return false when it should return true

#include <stdio.h>
#include <string.h>

int main()
{
    char* string="GET /cats.html HTTP/1.1\r\n";
    if(strncmp(string,"GET ",4)==0)
    {
        printf("hello");
        if(string[4]=='/')
        {
            printf(",\n");
            char* string1=strchr(string,'.');
            string1=strchr(string1,' ');
            printf("%s",string1);
            if(string1!=NULL)
            {
                if(*string1==" HTTP/1.1\r\n")
                {
                    printf("world\n");
                }
            }
        }
    }
}

Your compiler should warn. Never ignore compiler warnings. And enable the recommended warnings. — too honest for this site, Sep 08 '16 at 18:16
@islam zidan: `*string1==" HTTP/1.1\r\n"` is not valid C code. Your compiler undoubtedly told you about that. Did you just ignore your compiler's diagnostic messages? — AnT stands with Russia, Sep 08 '16 at 18:39

R Sahu · Accepted Answer · 2016-09-08T18:26:50.010

The line:

if(*string1==" HTTP/1.1\r\n")

does not compare whether two strings are equal.

type of string1 is char*. Hence type of *string1 is char.

Hence, you are comparing a char with a char const*, which is far from what you expected.

Even using

if(string1==" HTTP/1.1\r\n")

will not give you the expected result since it will compare two pointers for equality, which will be false in this use case all the time.

What you need to use is the library function to compare two strings.

if( strcmp(string1, " HTTP/1.1\r\n") == 0)

score 1 · Answer 2 · answered Sep 08 '16 at 18:09

1

Because you are not comparing strings, you are comparing pointers to strings.

The proper comparison would be:

if(!strcmp(string1," HTTP/1.1\r\n")) {
    ...
}

answered Sep 08 '16 at 18:09

Serge

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it worked thank you very much my reputation is still low so i can't vote and the answer will be accepted in 11 minutes – islam zidan Sep 08 '16 at 18:11
1

You got my "two cents" into your rep. ;) – Serge Sep 08 '16 at 18:12
@Serge: "...you are comparing pointers to strings...". Where does the OP compare pointers to strings? `*string1` is not a "pointer to string". – AnT stands with Russia Sep 08 '16 at 18:30

why are these two strings not equal in c

2 Answers2