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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: Portable way of reading str[4] as uint32_t
Date: Thu, 02 Apr 2020 19:09:07 -0700
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Spiros Bousbouras <spibou@gmail.com> writes:

> On Mon, 30 Mar 2020 23:28:33 -0700 (PDT)
> wyniijj@gmail.com wrote:
>
>> Richard Damon
>>
>>> On 3/30/20 2:42 PM, wyniijj@gmail.com wrote:
>>>
>>>> I'd like to read the value a.value in the following program as
>>>> 0x78563412 in a portable way, none of hton or ntoh is useful.
>>>> How should I do?
>>>>
>>>> #include <stdio.h>
>>>> #include <arpa/inet.h>
>>>>
>>>> int main()
>>>> {
>>>>  union {
>>>>    char str[4];
>>>>    uint32_t value;
>>>>  } a;
>>>>
>>>>  a.str[0]=0x12;
>>>>  a.str[1]=0x34;
>>>>  a.str[2]=0x56;
>>>>  a.str[3]=0x78;
>>>>
>>>>  printf("host= %08x\n",a.value);
>>>>  printf("hton= %08x\n",htonl(a.value));
>>>>  printf("ntoh= %08x\n",ntohl(a.value));
>>>>  return 0;
>>>> }

[...]

> I note also that to have  uint32_t  you need
> #include <stdint.h>

Actually not, because <arpa/inet.h> was already #include'd.
See for example the man page for htonl().