How to Compare 2 Character Arrays

Question

How do I compare these two character arrays to make sure they are identical?

char test[10] = "idrinkcoke"
char test2[10] = "idrinknote"

I'm thinking of using for loop, but I read somewhere else that I couldnt do test[i] == test2[i] in C.

I would really appreciate if someone could help this. Thank you.

You can do `test[i] == test2[i]`, since they are character comparisons. but to compare string, you need to use the function `strcmp()` — Haris, Nov 15 '16 at 08:25
`I read somewhere else that I couldnt do test[i] == test2[i] in C` - Where did you read this? — work.bin, Nov 15 '16 at 08:27
Use strncmp, avoid using strcmp. Aside of that - you are overflowing the memory here - you allocated 10 characters and you wrote 11 (10 characters from "idrinkcoke" and a null-terminator). — Zach P, Nov 15 '16 at 08:32

artm · Accepted Answer · 2019-03-12T20:46:11.353

23

but I read somewhere else that I couldnt do test[i] == test2[i] in C.

That would be really painful to compare character-by-character like that. As you want to compare two character arrays (strings) here, you should use strcmp instead:

if( strcmp(test, test2) == 0)
{
    printf("equal");
}

Edit:

There is no need to specify the size when you initialise the character arrays. This would be better:

char test[] = "idrinkcoke";
char test2[] = "idrinknote";
It'd also be better if you use strncmp - which is safer in general (if a character array happens to be NOT NULL-terminated).

if(strncmp(test, test2, sizeof(test)) == 0)

edited Mar 12 '19 at 20:46

answered Nov 15 '16 at 08:26

artm

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I see. I didn't know this before. Thank you. – ThomasWest Nov 15 '16 at 08:27
Don't you miss the "n" in your strncmp sample code? – Habib Mar 12 '19 at 19:11
@Habib yes I did, thanks. – artm Mar 12 '19 at 20:46

score 3 · Answer 2 · answered Nov 15 '16 at 08:27

You can use the C library function strcmp

Like this:

if strcmp(test, test2) == 0

From the documentation on strcmp:

Compares the C string str1 to the C string str2.

This function starts comparing the first character of each string. If they are equal to each other, it continues with the following pairs until the characters differ or until a terminating null-character is reached.

This function performs a binary comparison of the characters. For a function that takes into account locale-specific rules, see strcoll.

and on the return value:

returns 0 if the contents of both strings are equal

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How to Compare 2 Character Arrays

2 Answers2