/usr/bin/checkint is in netdiag 1.2-1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 | #!/bin/bash
echo "Active interfaces"
echo "-----------------"
/sbin/ifconfig | egrep "^[a-z]" | cut -d' ' -f1
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