regex - domain name regular expression not matching -

i have shell script @ /www/cgi-bin/test can access on network @ http://192.168.1.1/cgi-bin/test.

i attempting parse query string, should d=domain.com, , validate against regular expression:

#!/bin/sh  echo "content-type: text/html" echo ""  domain=${query_string#d=}  if [[ ! $domain =~ [a-za-z0-9-]+(\.[a-za-z0-9-]+)*(\.[a-za-z]{2,}) ]];     exit fi  echo "validation success!" 

when didn't work, tried using regex stole here:

if [[ ! $domain =~ \     ^(([a-za-z](-?[a-za-z0-9])*)\.)*[a-za-z](-?[a-za-z0-9])+\.[a-za-z]{2,}$ \ ]];     exit fi 

i can't regex match either. in both cases, tried escaping curly braces (\{2,\}) according advanced bash-scripting guide, didn't make difference.

in case it's relevant, platform i'm on openwrt 12.09.

edit: realized shell script might not support bash's [[ ... =~ ... ]] syntax. unfortunately openwrt doesn't ship bash.

if don't have bash, and/or cannot replace shebang #!/bin/bash, [[ expression might not work, or pattern substitution ${query_string#pattern} might not work.

in case, can use awk hit 2 birds 1 stone:

if ! echo $query_string | awk '$0 !~ /^d=[a-za-z0-9-]+(\.[a-za-z0-9-]+)*(\.[a-za-z]{2,})$/ {exit 1}';     exit 1 fi 

or, if pattern substitution works, , regex doesn't can use expr instead of awk:

domain=${query_string#d=} if ! expr $domain : '[a-za-z0-9-]\{1,\}\(\.[a-za-z0-9-]\{1,\}\)*\(\.[a-za-z]\{2,\}\)$' >/dev/null;     exit 1 fi 

in both cases, used bit more strict pattern d= in query_string. in both cases, careful end pattern $, otherwise things domain.com- pass.