/usr/share/doc/bash/examples/functions/isvalidip is in bash-doc 4.3-6ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | # Thanks to Chris F. A. Johnson <c.f.a.johnson@rogers.com> for this one
is_validip()
{
case "$*" in
""|*[!0-9.]*|*[!0-9]) return 1 ;;
esac
local IFS=.
set -- $*
[ $# -eq 4 ] &&
[ ${1:-666} -le 255 ] && [ ${2:-666} -le 255 ] &&
[ ${3:-666} -le 255 ] && [ ${4:-666} -le 254 ]
}
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