installed_for.sh

Light Bash utility to calculate elapsed time since OS installation.

Usage

Just execute the script: ./installed_for.sh

Compatible distributions

• Red Hat Enterprise Linux derivatives (CentOS, RHEL, Scientific Linux etc.) (using rpm -q basesystem)
• Fedora and derivatives (using rpm -q basesystem)
• Arch Linux based distributions (using /var/log/pacman.log)
• Debian based that utilize the /var/log/installer directory (using ls -lact --full-time /var/log/installer)

The list is far from complete and I am currently trying to find standard ways to determine installation dates avoiding workarounds.

All other distributions are currently (until a better method is found) supported using the filesystem creation date: ls -lact --full-time /etc

Implementation details

The script simply calculates the difference in seconds between current and installation datetime. There are some notable functions:

function displaytime $1 $2 $3

This function converts seconds (provided by $1 parameter) to the following format:

#a years #b days #c hours #d minutes #e seconds

However, it calculates leap years, for the shake of completeness, in order to convert correctly. To do so, $2(INSTALL_YEAR) and $3(CURRENT_YEAR) parameters are needed.