例：2文字目が p のユーザを探す
-bash-2.05b$ grep '^.p' /etc/passwd lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin operator:x:11:0:operator:/root:/sbin/nologin apache:x:48:48:Apache:/home/httpd:/bin/false -bash-2.05b$