```sh
#!/bin/sh
IPFW=/usr/obj/usr/src/amd64.amd64/sbin/ipfw/ipfw.full
tbl_block=4
${IPFW} table $tbl_block create type addr or-flush
while read -r line
do ${IPFW} table $tbl_block atomic add $line
done <<-HEREDOC
45.143.220.228/32
68.64.211.117/32
68.64.211.117/32
45.143.220.229/32
HEREDOC
```
Yields:
```
added: 45.143.220.228/32 0
added: 68.64.211.117/32 0
exists: 68.64.211.117/32 0
ipfw.full: Adding record failed: record already exists
added: 45.143.220.229/32 0
```
as expected