User lists

Hi everybody
I searching for a cgi or other script that extracts the userid of the
passwd file because I need to get a list of users in a special group to
give to them access to squid, i put the same group to them.
user1:x:455:150:name:/home:/dev/null
user2:x:456:150:name:/home:/dev/null
I was traing with grep and cat but i can´t get the excat lenght of the
uid for each one.

Thanks in advance.

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+-------------------------------------------------------------------+
| Gustavo Palacios (Mr.)           <gpalacios@petroecuador.com.ec>
| Network Administrator            <webmaster@petroecuador.com.ec>
| PETROECUADOR
| Empresa Estatal Petróleos del Ecuador
| P.O. Box 17-11-5007, Quito, Ecuador
| Phone: +593 (2) 563060, [Direct: +593 (2) 562502]
| Fax:   +593 (2) 503571
| Cell:  +593 (09) 844118
| WWW => http://www.petroecuador.com.ec
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