bswap(3)

🌸 bswap — byte swap, but make it fashion 💅

okay bestie, gather round, because we're about to talk about the cutest little function family in bswap(3) — it lives in the Library Functions Manual and honestly? it's giving "small but mighty." ✨

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✨ NAME ✨

bswap_16, bswap_32, bswap_64 — byte swap 🦋

📚 LIBRARY 📚

Standard C library (libc, -lc) — yeah, the classic one, she's everywhere 👑

🎀 SYNOPSIS 🎀

#include <byteswap.h>

uint16_t bswap_16(uint16_t x);
uint32_t bswap_32(uint32_t x);
uint64_t bswap_64(uint64_t x);

💖 DESCRIPTION 💖

so here's the vibe: these functions take a value and return it with the byte order flipped. that's it, that's the whole personality. 🙈

• bswap_16 flips the bytes of a 2-byte argument
• bswap_32 flips the bytes of a 4-byte argument
• bswap_64 flips the bytes of an 8-byte argument

the way that endianness just... reverses? iconic behavior fr fr. byte order reversal is the moment 🌈

⭐ RETURN VALUE ⭐

each one hands back the value of its argument, bytes reversed. same energy, opposite direction. 🫶

💀 ERRORS 💀

ngl these functions always succeed. no errors, no drama, no errno, nothing. they simply do not miss. ✨

👑 STANDARDS 👑

GNU. periodt. 💅

🌸 EXAMPLES 🌸

okay so the program below swaps the bytes of the 8-byte integer you hand it as a command-line argument. here's a whole little shell session showing it off:

$ ./a.out 0x0123456789abcdef;
0x123456789abcdef ==> 0xefcdab8967452301

look at that glow-up. 😭 the bytes literally did a 180 and ate. 🔥

🧚 Program source 🧚

here's the source, verbatim, no notes:

#include <byteswap.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char *argv[])
{
    uint64_t x;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <num>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    x = strtoull(argv[1], NULL, 0);
    printf("%#w64x ==> %#w64x\n", x, bswap_64(x));

    exit(EXIT_SUCCESS);
}

🦋 SEE ALSO 🦋

• byteorder(3)
• endian(3)

bestie reminder: if you're out here flipping bytes without checking your endianness first, that's not main character energy, that's just chaos. do a vibe check on your platform, okay? 💜

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and that's the whole page, bestie!! 💖✨

this lil' rewrite came to you from Linux man-pages 6.20, dated 2026-08-10 — like, that's the source and version and date, cute right? 🎀 go forth and swap those bytes, you absolute legend. 👑🌸