On Linux you can set a temporary environment variable in a shell. The process differs depending on the type of shell (csh, bash, tcsh) you are using.
1.Start a shell and enter:
echo $SHELL
2.If you are running a bash or ksh shell, use export to set the environment variable, for example:
export lightmap_LICENSE=/Shared/lightmap/licenses/hdrlightstudio.lic
3.If you are running a csh or tcsh shell, use setenv to set the environment variable, for example:
setenv lightmap_LICENSE /Shared/lightmap/licenses/hdrlightstudio.lic
In the above example, the environment variable (lightmap_LICENSE) only exists in this shell. For a permanent solution for you as a user, you'll need to add the environment variable to your .cshrc, .tcshrc, .bashrc, .kshrc file in your home directory. For a permanent, system wide solution, then get your systems administrator to add it to /etc/profile.