bswap_16, bswap_32, bswap_64 - reverse order of bytes

       These  functions  return  a value in which the order of the bytes in their 2-, 4-, or 8-byte arguments is
       reversed.

       These functions always succeed.

       The program below swaps the bytes of the 8-byte integer  supplied  as  its  command-line  argument.   The
       following shell session demonstrates the use of the program:

           $ ./a.out0x0123456789abcdef
           0x123456789abcdef ==> 0xefcdab8967452301

   Programsource

       #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("%#" PRIx64 " ==> %#" PRIx64 "\n", x, bswap_64(x));

           exit(EXIT_SUCCESS);
       }

       Standard C library (libc, -lc)

       bswap_16, bswap_32, bswap_64 - reverse order of bytes

       These functions return the value of their argument with the bytes reversed.

byteorder(3), endian(3)

Linux man-pages 6.9.1                              2024-06-15                                           bswap(3)

       GNU.

#include<byteswap.h>uint16_tbswap_16(uint16_tx);uint32_tbswap_32(uint32_tx);uint64_tbswap_64(uint64_tx);