9.12. 網路位址函式及運算子

Table 9.36shows the operators available for thecidrandinettypes. The operators<<,<<=,>>,>>=, and&&test for subnet inclusion. They consider only the network parts of the two addresses (ignoring any host part) and determine whether one network is identical to or a subnet of the other.

**Table 9.36. **cidrandinetOperators

Operator	Description	Example
<	is less than	inet '192.168.1.5' < inet '192.168.1.6'
<=	is less than or equal	inet '192.168.1.5' <= inet '192.168.1.5'
=	equals	inet '192.168.1.5' = inet '192.168.1.5'
>=	is greater or equal	inet '192.168.1.5' >= inet '192.168.1.5'
>	is greater than	inet '192.168.1.5' > inet '192.168.1.4'
<>	is not equal	inet '192.168.1.5' <> inet '192.168.1.4'
<<	is contained by	inet '192.168.1.5' << inet '192.168.1/24'
<<=	is contained by or equals	inet '192.168.1/24' <<= inet '192.168.1/24'
>>	contains	inet '192.168.1/24' >> inet '192.168.1.5'
>>=	contains or equals	inet '192.168.1/24' >>= inet '192.168.1/24'
&&	contains or is contained by	inet '192.168.1/24' && inet '192.168.1.80/28'
~	bitwise NOT	~ inet '192.168.1.6'
&	bitwise AND	inet '192.168.1.6' & inet '0.0.0.255'
`	`	bitwise OR	`inet '192.168.1.6'	inet '0.0.0.255'`
+	addition	inet '192.168.1.6' + 25
-	subtraction	inet '192.168.1.43' - 36
-	subtraction	inet '192.168.1.43' - inet '192.168.1.19'

Table 9.37shows the functions available for use with thecidrandinettypes. Theabbrev,host, andtextfunctions are primarily intended to offer alternative display formats.

**Table 9.37. **cidrandinetFunctions

Function	Return Type	Description	Example	Result
abbrev(inet)	text	abbreviated display format as text	abbrev(inet '10.1.0.0/16')	10.1.0.0/16
abbrev(cidr)	text	abbreviated display format as text	abbrev(cidr '10.1.0.0/16')	10.1/16
broadcast(inet)	inet	broadcast address for network	broadcast('192.168.1.5/24')	192.168.1.255/24
family(inet)	int	extract family of address;4for IPv4,6for IPv6	family('::1')	6
host(inet)	text	extract IP address as text	host('192.168.1.5/24')	192.168.1.5
hostmask(inet)	inet	construct host mask for network	hostmask('192.168.23.20/30')	0.0.0.3
masklen(inet)	int	extract netmask length	masklen('192.168.1.5/24')	24
netmask(inet)	inet	construct netmask for network	netmask('192.168.1.5/24')	255.255.255.0
network(inet)	cidr	extract network part of address	network('192.168.1.5/24')	192.168.1.0/24
set_masklen(inet,int)	inet	set netmask length forinetvalue	set_masklen('192.168.1.5/24', 16)	192.168.1.5/16
set_masklen(cidr,int)	cidr	set netmask length forcidrvalue	set_masklen('192.168.1.0/24'::cidr, 16)	192.168.0.0/16
text(inet)	text	extract IP address and netmask length as text	text(inet '192.168.1.5')	192.168.1.5/32
inet_same_family(inet,inet)	boolean	are the addresses from the same family?	inet_same_family('192.168.1.5/24', '::1')	false
inet_merge(inet,inet)	cidr	the smallest network which includes both of the given networks	inet_merge('192.168.1.5/24', '192.168.2.5/24')	192.168.0.0/22

Anycidrvalue can be cast toinetimplicitly or explicitly; therefore, the functions shown above as operating oninetalso work oncidrvalues. (Where there are separate functions forinetandcidr, it is because the behavior should be different for the two cases.) Also, it is permitted to cast aninetvalue tocidr. When this is done, any bits to the right of the netmask are silently zeroed to create a validcidrvalue. In addition, you can cast a text value toinetorcidrusing normal casting syntax: for example,inet(expression)orcolname::cidr.

Table 9.38shows the functions available for use with themacaddrtype. The functiontrunc(macaddr)returns a MAC address with the last 3 bytes set to zero. This can be used to associate the remaining prefix with a manufacturer.

**Table 9.38. **macaddrFunctions

Function	Return Type	Description	Example	Result
trunc(macaddr)	macaddr	set last 3 bytes to zero	trunc(macaddr '12:34:56:78:90:ab')	12:34:56:00:00:00

Themacaddrtype also supports the standard relational operators (>,<=, etc.) for lexicographical ordering, and the bitwise arithmetic operators (~,&and|) for NOT, AND and OR.

Table 9.39shows the functions available for use with themacaddr8type. The functiontrunc(macaddr8)returns a MAC address with the last 5 bytes set to zero. This can be used to associate the remaining prefix with a manufacturer.

**Table 9.39. **macaddr8Functions

Function	Return Type	Description	Example	Result
trunc(macaddr8)	macaddr8	set last 5 bytes to zero	trunc(macaddr8 '12:34:56:78:90:ab:cd:ef')	12:34:56:00:00:00:00:00
macaddr8_set7bit(macaddr8)	macaddr8	set 7th bit to one, also known as modified EUI-64, for inclusion in an IPv6 address	macaddr8_set7bit(macaddr8 '00:34:56:ab:cd:ef')	02:34:56:ff:fe:ab:cd:ef

Themacaddr8type also supports the standard relational operators (>,<=, etc.) for ordering, and the bitwise arithmetic operators (~,&and|) for NOT, AND and OR.