Você pode usar o squidclient:
squidclient -h localhost -p 3128 mgr:info
HTTP/1.0 200 OK
Server: squid/3.1.6
Mime-Version: 1.0
Date: Wed, 02 Mar 2011 06:51:49 GMT
Content-Type: text/plain
Expires: Wed, 02 Mar 2011 06:51:49 GMT
Last-Modified: Wed, 02 Mar 2011 06:51:49 GMT
X-Cache: MISS from localhost
X-Cache-Lookup: MISS from localhost:3128
Via: 1.0 localhost (squid/3.1.6)
Proxy-Connection: close
Squid Object Cache: Version 3.1.6
Start Time: Wed, 02 Mar 2011 06:50:08 GMT
Current Time: Wed, 02 Mar 2011 06:51:49 GMT
Connection information for squid:
Number of clients accessing cache: 1
Number of HTTP requests received: 1
Number of ICP messages received: 0
Number of ICP messages sent: 0
Number of queued ICP replies: 0
Number of HTCP messages received: 0
Number of HTCP messages sent: 0
Request failure ratio: 0.00
Average HTTP requests per minute since start: 0.6
Average ICP messages per minute since start: 0.0
Select loop called: 29980 times, 3.352 ms avg
...
Tente também mgr: refresh, mgr: counters, mgr: utilização, mgr: mem.