Squid on FreeBSD
Pre-Built Binary Packages
FreeBSD 12.2 ships squid-4.14 as a pre-built package, and squid-4.15 in the ports collection.
It also carries squid-5.0.5 under the name "squid-devel"
To install the binary package:
pkg add squid
The general build instructions should be all you need.
However, if you wish to integrate patching of Squid with patching of your other FreeBSD packages, it might be easiest to install Squid from the Ports collection. As of FreeBSD 12.2, the available ports are:
/usr/ports/www/squid3 - Squid 3.5.28
/usr/ports/www/squid3 - Squid 4.10
To install squid-4:
cd /usr/ports/www/squid make install clean
The FreeBSD packages and ports install squid in the following locations:
/usr/local/sbin - binaries (squid, squidclient, etc)
/usr/local/etc/squid - configurations (squid.conf, mime.conf, error pages)
/usr/local/etc/rc.d/squid - daemon control script
ERROR: Could not send signal N to process NN: (3) No such process
FreeBSD contains additional security settings to prevent users sending fatal or other signals to other users applications.
Unfortunately this catches Squid in the middle. Since the administrative process of Squid normally runs as root and the child worker process runs as some other non-privileged user (by default: nobody). The root administrative process is unable to send signals such as shutdown or reconfigure to its own child.