How do I get the real full package name (including the version) that would be installed if I ran apt-get install pseudo-package-name?

This is related to this previous question: Get the kernel version from lts package?

Example:

apt-get install linux-image-generic-lts-trusty

would install (as of right now on my 32-bit Trusty server):

linux-image-3.13.0-35-generic

I've tried the following, but none give me the answer. I'm trying to script this so I can just grab the linux-headers.

$ sudo apt-get install -qqs linux-image-generic-lts-trusty

Inst linux-image-generic-lts-trusty (3.13.0.35.42 Ubuntu:14.04/trusty-updates [i386])

Conf linux-image-generic-lts-trusty (3.13.0.35.42 Ubuntu:14.04/trusty-updates [i386])

$ apt-cache depends linux-image-generic-lts-trusty

linux-image-generic-lts-trusty

  Depends: linux-image-generic

$ apt-cache depends linux-image-generic

linux-image-generic

  Depends: linux-image-3.13.0-35-generic

  Depends: linux-image-extra-3.13.0-35-generic

  Depends: linux-firmware

$ apt-cache policy linux-image-generic-lts-trusty

linux-image-generic-lts-trusty:

  Installed: (none)

  Candidate: 3.13.0.35.42

  Version table:

     3.13.0.35.42 0

        500 http://us.archive.ubuntu.com/ubuntu/ trusty-updates/main i386 Packages

        500 http://security.ubuntu.com/ubuntu/ trusty-security/main i386 Packages

     3.13.0.24.28 0

        500 http://us.archive.ubuntu.com/ubuntu/ trusty/main i386 Packages

After some exploration of /var/lib/{apt,dpkg}, I relealized that there's not a generic, scriptable answer to this problem. So, similar to the answers below from @mchid and @muru, I did it like this:

#!/bin/bash



metapackage=linux-image-generic-lts-trusty

linux_package_version=$(apt-cache policy $metapackage |

    sed -nE '/Candidate:/ s,[^[:digit:]]*([[:digit:].]+).([[:digit:]]+).[[:digit:]]+,1-2,p')



apt-get download linux-headers-${linux_package_version}-generic linux-headers-${linux_package_version})