bswap - Man Page

reverse order of bytes


    #include <byteswap.h>

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


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.


These functions always succeed.

Conforming to

These functions are GNU extensions.


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.out 0x0123456789abcdef
0x123456789abcdef ==> 0xefcdab8967452301

Program source

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

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

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

    x = strtoull(argv[1], NULL, 0);
    printf("%#" PRIx64 " ==> %#" PRIx64 "\n", x, bswap_64(x));


See Also

byteorder(3), endian(3)


This page is part of release 5.13 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at

Referenced By

byteorder(3), endian(3).

The man pages bswap_16(3), bswap_32(3) and bswap_64(3) are aliases of bswap(3).

2021-06-20 Linux Programmer's Manual