get_domainname.c

[詳解]

/*++
/* NAME
/*  get_domainname 3
/* SUMMARY
/*  network domain name lookup
/* SYNOPSIS
/*  #include <get_domainname.h>
/*
/*  const char *get_domainname()
/* DESCRIPTION
/*  get_domainname() returns the local domain name as obtained
/*  by stripping the hostname component from the result from
/*  get_hostname().  The result is the hostname when get_hostname()
/*  does not return a FQDN form ("foo"), or its result has only two
/*  components ("foo.com").
/* DIAGNOSTICS
/*  Fatal errors: no hostname, invalid hostname.
/* SEE ALSO
/*  get_hostname(3)
/* LICENSE
/* .ad
/* .fi
/*  The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*  Wietse Venema
/*  IBM T.J. Watson Research
/*  P.O. Box 704
/*  Yorktown Heights, NY 10598, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <string.h>

/* Utility library. */

#include "mymalloc.h"
#include "get_hostname.h"
#include "get_domainname.h"

/* Local stuff. */

static char *my_domain_name;

/* get_domainname - look up my domain name */

const char *get_domainname(void)
{
    const char *host;
    const char *dot;

    /*
     * Use the hostname when it is not a FQDN ("foo"), or when the hostname
     * actually is a domain name ("foo.com").
     */
    if (my_domain_name == 0) {
    host = get_hostname();
    if ((dot = strchr(host, '.')) == 0 || strchr(dot + 1, '.') == 0) {
        my_domain_name = mystrdup(host);
    } else {
        my_domain_name = mystrdup(dot + 1);
    }
    }
    return (my_domain_name);
}