bswap(3) - BetterMan

bswap(3)

reverse order of bytes

distropkg manpages-dev@6.9.1-1dataset 2026-04-01T06:19:02Z+debian+ec4110e+mandoc:1.14.6-4

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
);

—

NAME

bswap_16, bswap_32, bswap_64 - reverse order of bytes

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

bash

#include <byteswap.h>

bash

uint16_t bswap_16(uint16_t \nx\n);\n
\nuint32_t bswap_32(uint32_t \nx\n);\n
\nuint64_t bswap_64(uint64_t \nx\n);

DESCRIPTION

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

RETURN VALUE

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

ERRORS

These functions always succeed.

STANDARDS

GNU.

EXAMPLES

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:

bash

$ \n./a.out 0x0123456789abcdef\n
0x123456789abcdef ==> 0xefcdab8967452301

Program source

bash

#include <byteswap.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
\n
    uint64_t x;
\n
    if (argc != 2) {
\n
        fprintf(stderr, "Usage: %s <num>\n", argv[0]);
\n
        exit(EXIT_FAILURE);
\n
    }
\n
    x = strtoull(argv[1], NULL, 0);
\n
    printf("%#" PRIx64 " ==> %#" PRIx64 "\n", x, bswap_64(x));
\n
    exit(EXIT_SUCCESS);
}