Apple - Installing .pkg with terminal ?

/usr/sbin/installer

The installer command is used to install Mac OS X installer packages to a specified domain or volume. The installer command installs a single package per invocation, which is specified with the -package parameter ( -pkg is accepted as a synonym). It may be either a single package or a metapackage. In the case of the metapackage, the packages which are part of the default install will be installed unless disqualified by a package's check tool(s).

See man installer for the full functionality. Often

sudo installer -pkg /path/to/package.pkg -target /

is all that's needed. Here / is the mount point of Macintosh HD volume. -target accepts path like "/Volumes/Macintosh HD", or /dev/disk0 also.

Just in case it's needed; if you want to installer a .pkg without root access:

installer -pkg myapp.pkg -target CurrentUserHomeDirectory

will install the package in ~/Applications.

Install all .pkg files from the current folder to /Applications:

for f in *.pkg ; 
    do sudo installer -verbose -pkg "$f" -target /
done

As an alternative you can install the packages to your home folder with -target ~. They will end up in /Users/<your_account>/Applications unless a specific path is predefined in the installer.

^{If you need to see what exactly a pkg installer script contains and what pre- and post-install scripts will be run then check out SuspiciousPackage (freeware), and use quick preview from Finder when a .pkg file is selected. Pressing spacebar in Finder with the selected file should work too.}