gethostid 的实现

最新推荐文章于 2024-12-19 21:17:05 发布

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最新推荐文章于 2024-12-19 21:17:05 发布

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分类专栏： C/c++ 文章标签： Linux

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本文提供了一种在不使用系统提供的gethostid函数的情况下，自行实现获取本地主机唯一标识符的方法。详细阐述了实现过程，包括使用gethostname、gethostbyname等函数来获取主机名和IP地址，并解释了该方法适用于哪些场景。

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static long gethostid(void)
{
   long result = 0;
    char name[1024];
    struct hostent *hent = NULL;
    char **p = NULL;
    struct in_addr in;
    if (gethostname(name, 1024) == 0)
    {
if ((hent = gethostbyname(name)) != NULL)
{
            p = hent->h_addr_list;
            if (p && *p)
            {
                (void) memcpy(&in.s_addr, *p, sizeof(in.s_addr));
                result = (long)in.s_addr;
            }
        }
    }
   return result;
}

gethostid

man page 上这样子描述

GETHOSTID(2) Linux Programmer's Manual GETHOSTID(2)

NAME
gethostid, sethostid - get or set the unique identifier of the current host

SYNOPSIS
#include <unistd.h>

long gethostid(void);
int sethostid(long hostid);

DESCRIPTION
Get or set a unique 32-bit identifier for the current machine. The 32-bit identifier is intended to be unique among all UNIX systems in existence. This
normally resembles the Internet address for the local machine, as returned by gethostbyname(3), and thus usually never needs to be set.

The sethostid() call is restricted to the superuser.

The hostid argument is stored in the file /etc/hostid.

RETURN VALUE
gethostid() returns the 32-bit identifier for the current host as set by sethostid(2).

CONFORMING TO
4.2BSD; these functions were dropped in 4.4BSD. SVr4 includes gethostid() but not sethostid(). POSIX.1-2001 specifies gethostid() but not sethostid().

FILES
/etc/hostid

EXAMPLE
id = gethostid ();

/* This is a no-op unless unsigned int is wider than 32 bits. */
id &= 0xffffffff;

SEE ALSO
hostid(1), gethostbyname(3)