Is there a way of getting the Canonical Time Zone name from a Linux shell script? for example, if my configured time zone is PDT, then I would like to get "America/Los_Angeles".
I know I could get from the symbolic link /etc/localtime if it were configured, but as it might not be configured in all servers I cannot rely on that one.
On the other hand, I can get the short time zone name with the command date +%Z, but I still need the canonical name.
Is there a way to either get the canonical name of the current time zone or transform the time zone gotten with the date +%Z command, even if the symbolic link /etc/localtime is not set?
This is more complicated than it sounds. Most linux distributions do it differently so there is no 100% reliable way to get the Olson TZ name.
Below is the heuristic that I have used in the past:
- First check /etc/timezone, if it exists use it.
- Next check if /etc/localtime is a symlink to the timezone database
- Otherwise find a file in /usr/share/zoneinfo with the same content
as the file /etc/localtime
Untested example code:
if [ -f /etc/timezone ]; then
OLSONTZ=`cat /etc/timezone`
elif [ -h /etc/localtime ]; then
OLSONTZ=`readlink /etc/localtime | sed "s/\/usr\/share\/zoneinfo\///"`
else
checksum=`md5sum /etc/localtime | cut -d' ' -f1`
OLSONTZ=`find /usr/share/zoneinfo/ -type f -exec md5sum {} \; | grep "^$checksum" | sed "s/.*\/usr\/share\/zoneinfo\///" | head -n 1`
fi
echo $OLSONTZ
Note that this quick example does not handle the case where multiple TZ names match the given file (when looking in /usr/share/zoneinfo). Disambiguating the appropriate TZ name will depend on your application.
-nick
