string compareto 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 - In C, strcmp() is a built-in library function used to compare two strings lexicographically.

Videos

Programming with C: Functions & Comparing Strings - YouTube

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

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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

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

String Comparison in C - Scaler Topics

January 11, 2024 - Comparing two strings or string comparison in C involves finding out if they are the same or not. This is done by using some built-in function or comparing the strings character by character to determine if they are equal.

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; }

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 ...

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

strcmp in C – How to Compare Strings in C

April 27, 2023 - The strcmp() function is part of the standard C library ( string.h ). Its primary purpose is to compare the characters of the two strings in sequence until it finds a mismatch or until the end of the strings is reached (that is, the null character ...

w3schools.com › c › ref_string_strcmp.php

C string strcmp() Function

For this comparison characters at the same position from both strings are compared one by one, starting from the left until one of them does not match or the end of a string has been reached.

quora.com › How-can-we-compare-two-strings-efficiently-in-C-or-C

How can we compare two strings efficiently in C or C++? - Quora

Answer (1 of 6): There is no way to compare strings efficiently. because they are strings. Is far better to compare 2 numbers than 2 strings. because when you compare numbers you ony need to compare 1 number. and such number can never be null. ...

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reddit.com › r/cpp_questions › simple comparison between std::string and c-string

r/cpp_questions on Reddit: simple comparison between std::string and c-string

August 26, 2023 -

Hello,

I am discussing with a person who believes that

std::string msg = "Hello";

if (msg == "Hello") { // UB?
   ...
}

According to the person, this line "if (msg == "Hello") {" is UB.

Have you seen this "operator==" as UB?

I have checked the C++ specification (from c++11), and it's acceptable. I checked the std::string implementation (GNU GCC 5 and the latest) and operator== calls std::string::compare and then "traits". Passing cstring in operator== is fine too...

Toolchain is ARM for 32bit architecture and std is c++11/14.

His arguments are based on Stackoverflow posts which are more than 10y ago...

Thank you

That person has probably misunderstood a post referring to comparing string literals. In C/C++ doing something like: char string[] = "test"; if (string == "test") { ... } Which isn't technically UB, but it certainly doesn't do what you're probably expecting. C/C++ have no built-in string comparator, what you're comparing here is the pointers, one being the pointer to a stack buffer of character and the other being a pointer to the raw string literal, which will not point to the same thing. What's UB as far as I know is this: const char* string = "test"; if (string == "test") { ... } If I remember correctly the standard doesn't specify that two identical string literals defined in your code can't be placed twice in the binary, so even if this check will pass on basically any compiler, it's still UB std::string does the right thing for you since it implements operator== between it and a null terminated string which does an actual comparison of the characters. Long story short, your friend is wrong.

As long as the c string is null terminated, it's fine.

TestMu AI Community

community.testmuai.com › ask a question

How should I compare strings correctly in C? - TestMu AI Community

June 19, 2025 - I’m building a simple C program that asks the user to input a word or character, stores it, and keeps printing it until the user types the same input again to exit. However, even when the user retypes the original input, the loop doesn’t stop. Am I using the wrong method for string comparison in C? I’m aware that using check != input may not be the correct approach, but I’m unsure how to properly handle this.

geeksforgeeks.org › c++ › stdstringcompare-in-c

std::string::compare() in C++ - GeeksforGeeks

May 6, 2025 - The string::compare() function in C++ is used to compare a string or the part of string with another string or substring. It is the member function of std::string class defined inside <string> header file.

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

C Language: strcmp function (String Compare)

In the C Language, the required header for the strcmp function is: ... /* Example using strcmp by TechOnTheNet.com */ #include <stdio.h> #include <string.h> int main(int argc, const char * argv[]) { /* Create a place to store our results */ int result; /* Create two arrays to hold our data */ char example1[50]; char example2[50]; /* Copy two strings into our data arrays */ strcpy(example1, "C programming at TechOnTheNet.com"); strcpy(example2, "C programming is fun"); /* Compare the two strings provided */ result = strcmp(example1, example2); /* If the two strings are the same say so */ if (result == 0) printf("Strings are the same\n"); /* If the first string is less than the second say so (This is because the 'a' in the word 'at' is less than the 'i' in the word 'is' */ if (result < 0) printf("Second string is less than the first\n"); return 0; }

digitalocean.com › community › tutorials › compare-strings-in-c-plus-plus

3 Ways to Compare Strings in C++ | DigitalOcean

April 22, 2024 - OutputString 1: String Match String 2: String Match Both the input strings are equal. strcmp(str_inp1, str_inp2) results in 0. The values of str_inp1 and str_inp2 are the same. C++ has a built-in compare() function to compare two strings.

en.cppreference.com › w › cpp › string › basic_string › compare.html

Then compare the sequences by calling Traits::compare(data1, data2, rlen). For standard strings this function performs character-by-character lexicographical comparison.

cplusplus.com › reference › cstring › 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.

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

String/Array Comparison (The GNU C Library)

Next: Collation Functions, Previous: Truncating Strings while Copying, Up: String and Array Utilities [Contents][Index] You can use the functions in this section to perform comparisons on the contents of strings and arrays. As well as checking for equality, these functions can also be used ...

Microsoft Learn

learn.microsoft.com › en-us › dotnet › csharp › how-to › compare-strings

How to compare strings - C# | Microsoft Learn

The strings are sorted using the List<T>.Sort method. This method needs a delegate that compares and orders two strings. The String.CompareTo method provides that comparison function.

docs.particle.io › reference › device-os › api › string-class › compareto

compareTo() - String class | Reference | Particle

The strings are compared character by character, using the ASCII values of the characters. That means, for example, that 'a' comes before 'b' but after 'A'. Numbers come before letters. String comparison only compares the 8-bit ASCII values. It does not compare UTF-8 encoded strings properly.

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

r/cprogramming 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

Two problems I can think of, off the top: Alignment. Some processors might want accesses to be aligned on certain boundaries, so the uint32_t access of an arbitrary string could be problematic. I think you're making an assumption that len is no larger than the size of the largest string. If someone were to pass in a "len" that was much larger than either string (e.g. both strings are in a buffer of a max size, and they pass in the max size), then you could easily walk off the end of the strings in the first loop, since you're not checking for the null terminator. And I just don't know if the semantics of strncmp requires that to not be true (that len can't be arbitrary). Since you'd be potentially comparing beyond the end of the string, you could say two equal strings aren't, since you're looking at characters past the null terminator.

Two thing impact performance: Number of instructions and data access. I am guessing this is a 32bit processor? Are you using DDR memory? Does your CPU have a data cache? If your CPU supports 32 bit read/writes, what you are doing makes sense. If your CPU has a data cache and DDR memory you can get down into cache line length to optimize for bursting. If you are coding for an ARM, consider using Neon intrinsics.

cplusplus.com › forum › beginner › 34698

Is there a string compareTo() ? - C++ Forum

If you're not familiar with this, imagine comparing 2 strings · Result will become a negative value since "Hello" comes before "Yo" in an alphabetic order. Comparing str2.compareTo(str1) would generate a positive value. Does this exists in C++? filipe (1165) str1 > str2 would evaluate to false.