exporting PATH not working in a bash shell on linux

Question

For example, I type to the following command:

         # PATH=$PATH:/var/test
         # echo $PATH
           ........./var/test       // working
         # export PATH

Next, I open another bash shell session to test if the export works by typing the following command:

         # echo $PATH
          ........      // not working as in I don't see /var/test path

Answer 1

you have set the PATH environment variable only for your current bash session. You need to add the line PATH=$PATH:/var/test into ~/.bashrc so that it works for any bash shell.

Just run the following command to put it into your rc(run commands) file (rc files contain startup information for a command(initialization)):
echo "PATH=$PATH:/var/test" >> ~/.bashrc

More info: https://en.wikipedia.org/wiki/Run_commands
https://superuser.com/questions/789448/choosing-between-bashrc-profile-bash-profile-etc

exporting a variable makes it available only in child processes spwaned/started from that bash shell.
As an example:

$ export var=abcd
$ sh
$ echo "$var"
abcd
$ exit
$ echo "$var"
abcd
$

sh is the child process of bash hence it gets the value of var, since you open a new bash which is a different process altogether it does get the PATH value.