Bash variables and types

Question

I'm making a script that validate an IP address. I do this:

read pool checkIp() { local ip=$1 local stat=1 if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then OIFS=$IFS IFS='.' ip=($ip) IFS=$OIFS [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]] stat=$? fi return $stat } checkIp $pool if [ $? -eq 0 ] then echo "valid" else echo "invalid" fi

The problem is that now the requirement is to valid that from the 2nd octet the input can contain the wildcard "*" (i think is better to use CIDR notation but is not the case), and now i can't use -le because if there is not a number, it fails.

I'd tried some forms but all conversions fails.

Not really into network addressing. Is “1.2.*.4” valid (my answer allows it), or as soon a “” is encountered the remaining pieces have to also be “”s? — manatwork
– manatwork, Commented Jan 30, 2013 at 14:23
Note that allowing 010.010.010.010 could cause confusion as most applications and library functions (gethostbyname, inet_addr...) consider it the same as 8.8.8.8 while some other the same as 10.10.10.10 (inet_pton). — Stéphane Chazelas
– Stéphane Chazelas, Commented Jan 30, 2013 at 15:27

Community · Accepted Answer · 2017-04-13 12:36:44Z

With a little additional rewrite. (As you use Bash-specific regular expression, just populate the BASH_REMATCH array instead of manipulating a word splitting.)

checkIp() { local ip="$1" if [[ "$ip" =~ ^([0-9]{1,3})\.([0-9]{1,3}|\*)\.([0-9]{1,3}|\*)\.([0-9]{1,3}|\*)$ ]]; then for ((i=1;i<=4;i++)); do [[ "${BASH_REMATCH[i]}" == '*' || "${BASH_REMATCH[i]}" -le 255 ]] || return 1 done return 0 fi return 1 }

Update according to owner's comment to disallow numbers after “*”:

checkIp() { local ip="$1" local asterisk='' if [[ "$ip" =~ ^([0-9]{1,3})\.([0-9]{1,3}|\*)\.([0-9]{1,3}|\*)\.([0-9]{1,3}|\*)$ ]]; then for ((i=1;i<=4;i++)); do [[ "${BASH_REMATCH[i]}" == '*' || ( ! "$asterisk" && "${BASH_REMATCH[i]}" -le 255 ) ]] || return 1 [[ "${BASH_REMATCH[i]}" == '*' ]] && asterisk='1' done return 0 fi return 1 }

Stéphane Chazelas · Accepted Answer · 2013-01-30 15:33:51Z

For the record, with zsh, you could write it:

[[ $ip = <0-255>.(<0-255>|"*").(<0-255>|"*").(<0-255>|"*") ]]

Note that it allows 000001.0000255.*.0, but not 0377.1.1.1 (even though 0377 as taken as an octal number is within range), because it only considers decimal numbers.

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