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

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.

 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.