c string equals in c - Brave Search

How do I properly compare strings in C?

stackoverflow.com › questions › 8004237 › how-do-i-properly-compare-strings-in-c

You can't (usefully) compare strings using != or ==, you need to use strcmp:

while (strcmp(check,input) != 0)

The reason for this is because != and == will only compare the base addresses of those strings. Not the contents of the strings themselves.

Answer from Mysticial on Stack Overflow

stackoverflow.com › questions › 8004237 › how-do-i-properly-compare-strings-in-c

How do I properly compare strings in C? - Stack Overflow

You can't (usefully) compare strings using != or ==, you need to use strcmp:

while (strcmp(check,input) != 0)

The reason for this is because != and == will only compare the base addresses of those strings. Not the contents of the strings themselves.

Ok a few things: gets is unsafe and should be replaced with fgets(input, sizeof(input), stdin) so that you don't get a buffer overflow.

Next, to compare strings, you must use strcmp, where a return value of 0 indicates that the two strings match. Using the equality operators (ie. !=) compares the address of the two strings, as opposed to the individual chars inside them.

And also note that, while in this example it won't cause a problem, fgets stores the newline character, '\n' in the buffers also; gets() does not. If you compared the user input from fgets() to a string literal such as "abc" it would never match (unless the buffer was too small so that the '\n' wouldn't fit in it).

geeksforgeeks.org › c language › strcmp-in-c

strcmp() in C %%sep%% %%sitename%% - GeeksforGeeks

December 13, 2025 - Explanation: In this code, strcmp is used to compare two strings, s1 and s2. Since both strings are identical ("g f g"), strcmp returns 0, indicating the strings are equal. The program then prints "Equal".

Videos

Programming with C: Functions & Comparing Strings - YouTube

Check If Strings Are Equal Using Recursion | C Programming Example ...

Comparing Strings in C using strcmp(): Complete Guide with Library ...

August 29, 2023

How to use strcmp function to compare two strings in C - YouTube

Comparing Strings in C using strcmp: Explained with Examples - YouTube

August 29, 2023

Compare strings without using strcmp() function in C programming||C ...

August 14, 2022

People also ask

How do we compare a substring of a string in C?

To compare a substring in C, you can use `strncmp()`, which compares a specified number of characters from two strings. Another method involves manually iterating through the desired portion of the string and comparing it character by character. Ensure that the substring is of the same length for a valid comparison.

upgrad.com › home › tutorials › software & tech › string comparison in c

String Comparison in C: Methods & Examples

What is string comparison in C?

String comparison in C is the process of determining whether two strings are equal, or which one is lexicographically greater or smaller. C doesn't have a built-in string data type, so strings are typically arrays of characters. This makes string comparison crucial for tasks like sorting, searching, and validation in C programs.

upgrad.com › home › tutorials › software & tech › string comparison in c

String Comparison in C: Methods & Examples

Can we compare strings in C without `strcmp()`?

Yes, strings in C can be compared manually by iterating over each character of both strings. You can use a loop to check if each character is the same. If you find a mismatch or reach the end of a string, you can conclude the comparison, returning values similar to `strcmp()` results.

upgrad.com › home › tutorials › software & tech › string comparison in c

String Comparison in C: Methods & Examples

programiz.com › c-programming › library-function › string.h › strcmp

C strcmp() - C Standard Library

#include <stdio.h> #include <string.h> int main() { char str1[] = "abcd", str2[] = "abCd", str3[] = "abcd"; int result; // comparing strings str1 and str2 result = strcmp(str1, str2); printf("strcmp(str1, str2) = %d\n", result); // comparing strings str1 and str3 result = strcmp(str1, str3); printf("strcmp(str1, str3) = %d\n", result); return 0; }

upgrad.com › home › tutorials › software & tech › string comparison in c

String Comparison in C: Methods & Examples

May 5, 2025 - The strings are equal. ... We use a `while` loop to compare each character in both strings.

scaler.com › home › topics › string comparison in c

String Comparison in C - Scaler Topics

January 11, 2024 - The strcmp() function compares both strings characters. If both strings have the same character at the same index till all of the characters have been compared or the pointer reaches the null character '\0' in both strings then we can say that ...

techonthenet.com › c_language › standard_library_functions › string_h › strcmp.php

C Language: strcmp function (String Compare)

string.h · In the C Programming Language, the strcmp function returns a negative, zero, or positive integer depending on whether the object pointed to by s1 is less than, equal to, or greater than the object pointed to by s2. The syntax for the strcmp function in the C Language is: int ...

en.cppreference.com › w › c › string › byte › strcmp

strcmp - cppreference.com

#include <stdio.h> #include <string.h> void demo(const char* lhs, const char* rhs) { const int rc = strcmp(lhs, rhs); const char* rel = rc < 0 ? "precedes" : rc > 0 ? "follows" : "equals"; printf("[%s] %s [%s]\n", lhs, rel, rhs); } int main(void) { const char* string = "Hello World!"; demo(string, "Hello!"); demo(string, "Hello"); demo(string, "Hello there"); demo("Hello, everybody!"

Find elsewhere

Google Bing Mojeek

cplusplus.com › reference › cstring › strcmp

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.

freecodecamp.org › news › strcmp-in-c-how-to-compare-strings-in-c

strcmp in C – How to Compare Strings in C

April 27, 2023 - I stored the output of the strcmp() function in a new variable named result, like earlier. The if statement checks the value of result and prints out the corresponding message depending on whether the strings are equal, or which string is less ...

stackoverflow.com › questions › 3933614 › using-the-equality-operator-to-compare-two-strings-for-equality-in-c

Using the equality operator == to compare two strings for equality in C - Stack Overflow

Because argv[1] (for instance) is actually a pointer to the string. So all you're doing is comparing pointers.

You can't compare strings in C with ==, because the C compiler does not really have a clue about strings beyond a string-literal.

The compiler sees a comparison with a char* on either side, so it does a pointer comparison (which compares the addresses stored in the pointers)

upgrad.com › home › tutorials › software & tech › strcmp in c

strcmp in C | String Comparison Function with Examples

February 5, 2025 - The strcmp in C function is used to compare two strings character by character. It returns 0 if both strings are equal, a positive value if the first string is greater, and a negative value if it’s smaller.

quora.com › How-do-I-check-if-two-strings-are-equal-in-C-1

How to check if two strings are equal in C - Quora

Answer (1 of 3): You can check whether two strings are equal or not by using strcmp() function. This is a built-in string function which is present in string.h header file. strcmp() function takes 2 strings as parameters and returns integer ...

labex.io › questions › how-to-compare-strings-in-c-136079

How to Compare Strings in C | LabEx

July 25, 2024 - Learn how to compare strings in C using strcmp function, characterbycharacter methods, and wildcard matching for effective programming.

gnu.org › software › libc › manual › html_node › String_002fArray-Comparison.html

String/Array Comparison (The GNU C Library)

The sign of the value indicates the relative ordering of the first part of the strings that are not equivalent: a negative value indicates that the first string is “less” than the second, while a positive value indicates that the first string is “greater”. The most common use of these functions is to check only for equality.

naukri.com › code360 › library › string-compare-in-c

String compare in C - Naukri Code 360

Almost there... just a few more seconds

reddit.com › r/learnprogramming › fast string comparisons in c

r/learnprogramming on Reddit: Fast String comparisons in C

October 29, 2023 -

Hi, I'm working just for fun on a fast comparison for strings written in C, with the intent of being faster than the normal strncmp function, which is currently the code bellow

```
int fast_strncmp(const char *str1, const char *str2, int len) {
    const char *final_pos = (str1 + len) - 4;
    while (str1 < final_pos) {
        // if characters differ, or end of the second string is reached
        if (*((uint32_t *)str1) != *((uint32_t *)str2)) {
            break;
        }
        // move to the block of characters
        str1 += 4;
        str2 += 4;
    }
    final_pos += 4;
    while (str1 < final_pos) {
        if (*str1 != *str2 || *str1 == 0 || *str2 == 0) {
            return *str1 - *str2;
        }
        // move to the next pair of characters
        str1++;
        str2++;
    }
    return 0;
}
```

Is there any clear problem with the code that could make it a bad option for fast string comparisons. When I wrote it a couple of weeks ago, I didn't think there could be any problem with it, but this week I was watching a couple of videos about C programming and it was mentioned that casting an array of 4 uint8_t to a uint32_t could be a problem. I'm even using this function at work and haven't had a single problem or warning, but since I'm planning to make a youtube video about it, I want to guarantee that my code won't be a problem for other people.

On top of that I've made a couple of benchmarks on the performance to be sure it really is fast, so I've compared it to strncmp and an implementation by https://github.com/mgronhol, that I found here: https://mgronhol.github.io/fast-strcmp/, which got me the following results:

EDIT: reddit was not cooperating with me posting the results text in a well formatted way, so here's the link to the file:

https://github.com/BenjamimKrug/fast_string_comparison/blob/main/results.txt

As you can see, running on the STM32 and the ESP32, my algorithm runs faster by a little compared to the fast_compare function by mgronhol, but running on my PC, it's performing terribly. Does anyone know why that is?

You can find more info about the code in my github repository where I put everything related to this test: https://github.com/BenjamimKrug/fast_string_comparison

P.S.: Sorry if this is the wrong subreddit for this kind of thing, I was going to post it on r/programming, but after reading the rules, I saw that maybe it was best to post it here.

EDIT: fixed code formatting

The problem with the cast is that the pointers might be unaligned, potentially causing slowdowns or even crashes in the worst case when dereferenced. To fix that you need to check the alignment of both pointers at entry and work with the largest possible blocks whose alignment requirements match the least aligned string. Other than that, if I recall correctly the C standard allows casting between any pointer type and char or void pointers, so if you implement the aforementioned fix you should be fine. As for the performance of the code, heavily optimized strncmp implementations use compiler intrinsics that produce SIMD instructions. For example on a modern x86-64 CPU with AVX512 you can check whether two properly aligned 64 8-bit blocks are equal with a single instruction.

First you do const char *final_pos = (str1 + len) - 4; Then, to clean up any dangling characters, you do final_pos += 4; If the strings are not null-terminated, then you risk running past the end. Taking a size parameter implies that the strings don't need a terminator for your function to work properly, when in fact they do. In addition, if the string length is a multiple of four, you always compare the last four chars one byte at a time. This aren't major problems, but I feel there's a slightly better approach to handling the end pointer: Instead, try doing int remainder = len % 4; const char *final_pos = (str1 + len) - remainder; Then final_pos += remainder;

reddit.com › r/c_programming › this is a super noob question, but strcmp returns 0 if the strings are equal and "truthy" if they are not equal, like if(-1) is true? is there a different way to compare strings or do i just need to wrap my head around this?

r/C_Programming on Reddit: This is a super noob question, but strcmp returns 0 if the strings are equal and "truthy" if they are not equal, like if(-1) is true? Is there a different way to compare strings or do I just need to wrap my head around this?

October 16, 2023 -

I am an experienced dev, but have no C experience and i'm currently working through reverse engineering one of the flipper zero apps and this really caught me off guard

I'm very sorry if this has been explained before I'm just trying to wrap my head around it

strcmp returns 0 => the strings are equal 1 => the first string is "after" the second when sorted -1 => the first string is "before" the second when sorted It's not really a function to tell you if 2 strings are equal, it's to tell you which "order" the 2 strings are in. It just coincidentally is usable to tell you if 2 strings are equal, because if they are it returns 0 Anything non-zero means the strings aren't equal

It's a comparison function, not an equality function. C#'s String.Compare, Java's String.compareTo, Go's strings.Compare, etc. are equivalent. If you want a simple "streq" or something you can just wrap the strcmp call. bool streq(const char *l, const char *r) { return strcmp(l, r) == 0; }

docs.vultr.com › clang › standard-library › string-h › strcmp

C string.h strcmp() - Compare Two Strings | Vultr Docs

September 27, 2024 - The strcmp() function in C is a versatile and powerful tool for comparing two strings. Understanding the integer it returns enables the determination of not only the equality but also the lexical order of strings.

cplusplus.com › reference › string › string › compare

std::string::compare

Compares the value of the string object (or a substring) to the sequence of characters specified by its arguments. The compared string is the value of the string object or -if the signature used has a pos and a len parameters- the substring that begins at its character in position pos and spans ...

quora.com › Can-we-compare-two-strings-using-in-C

Can we compare two strings using == in C? - Quora

Answer (1 of 4): Answer on applies only on C strings (char array), not c++ string :- The answer to your question is no, we cannot compare two strings using == in C because a string in C language is an array of characters and the name of the ...