std::strncmp(3)

✨ std::strncmp ✨

okay so bestie, welcome to the std::strncmp page from the C++ Standard Library 💅 this one lives in <cstring> and it's literally the girlie you call when you need to compare strings but like... only a little bit of them? no cap.

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🌸 SYNOPSIS 🌸

int strncmp( const char* lhs, const char* rhs, std::size_t count );

Defined in header <cstring>.

So what does she do? She compares at most count characters of two possibly null-terminated arrays. The comparison is done lexicographically, bestie. And here's the tea: characters following the null character are not compared — she stops there, periodt.

The sign of the result is the sign of the difference between the values of the first pair of characters (both interpreted as unsigned char) that differ in the arrays being compared. iykyk 🔥

⚠️ REAL TALK WARNING: The behavior is undefined when access occurs past the end of either array lhs or rhs. The behavior is also undefined when either lhs or rhs is the null pointer. Like... don't do that. Please. For me. 🙈

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🎀 PARAMETERS 🎀

• lhs, rhs — pointers to the possibly null-terminated arrays to compare 🫶
• count — maximum number of characters to compare ✨

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💖 RETURN VALUE 💖

• Negative value if lhs appears before rhs in lexicographical order 🌈
• Zero if lhs and rhs compare equal, or if count is zero ⭐
• Positive value if lhs appears after rhs in lexicographical order 👑

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🦋 NOTES 🦋

Heads up bestie: this function is not locale-sensitive, unlike std::strcoll and std::strxfrm. So she does her own thing, no outside opinions. 💅

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🌺 EXAMPLE 🌺

Run this code — go on, you know you want to ✨

#include <cstring>
#include <iostream>

void demo(const char* lhs, const char* rhs, int sz)
{
    const int rc = std::strncmp(lhs, rhs, sz);
    if (rc < 0)
        std::cout << "First " << sz << " chars of ["
                  << lhs << "] precede [" << rhs << "]\n";
    else if (rc > 0)
        std::cout << "First " << sz << " chars of ["
                  << lhs << "] follow [" << rhs << "]\n";
    else
        std::cout << "First " << sz << " chars of ["
                  << lhs << "] equal [" << rhs << "]\n";
}

int main()
{
    demo("Hello, world!", "Hello, everybody!", 13);
    demo("Hello, everybody!", "Hello, world!", 13);
    demo("Hello, everybody!", "Hello, world!", 7);
    demo("Hello, everybody!" + 12, "Hello, somebody!" + 11, 5);
}

Output: 👇

First 13 chars of [Hello, world!] follow [Hello, everybody!]
First 13 chars of [Hello, everybody!] precede [Hello, world!]
First 7 chars of [Hello, everybody!] equal [Hello, world!]
First 5 chars of [body!] equal [body!]

not the pointer arithmetic at the end slaying like that 😭🔥

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🧚 SEE ALSO 🧚

• strcmp — compares two strings (function) 🌸
• wcsncmp — compares a certain amount of characters from two wide strings (function) 💜
• memcmp — compares two buffers (function) 🍓
• strcoll — compares two strings in accordance to the current locale (function) 🌈
• C documentation for strncmp 📚

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okay that's the whole page bestie, you ate that 💅✨ sign-off time: this was served fresh from cppreference.com, vibes dated 2024.06.10, page std::strncmp(3) — go forth and compare responsibly 🫶👑