Environment Variable
 

i m new in linux so i want to ask about environment variable...i know about the file for individualk user we use to set environment variables..but on the command line how do we set them???for example i want to set ORACLE_SID=ORCL......how would i set it??? which command would i use??? on windows we just write
c:\set oracle_sid=orcl
u see that on windows its not case sensitive also...so are environment variables case sensitive on linux and which command do we use to set them and also tell me that which command do we use to see the newly set value and also that how do we add aother value to an existiung environment variable..for example if PATH=/usr/bin and i also want PATH=/abc..how willl i do that i could retain the old value and add the new value to PATH environment variable
Regards

in shell: export ORACLE_SID="value"

answer for PATH question

you have PATH set for example to "/bin"

and want to add same others values:

export PATH=$PATH:"/usr/bin":"/usr/local/bin"

I forgot,
to see values
echo $PATH