Thank Bo lan,
i have run the apt-get update but i haven't run apt-get upgrade or dist-upgrade. so i think i am still safe.
actually i was assuming that if there is a command to install update package specifically from test or sid like "apt-get install <package name>/<repository name>" in same way i though i could run some thing like "apt-get upgrade/stable" you know just thinking my way :P never mind............
actually few days back there is a package nethogs was up date in wheeze and old in squeeze. so instead of compiling from source i though i could install it from repo.
and what i did i just add the link to repository
deb
http://http.debian.net/debian wheezy main
deb-src
http://http.debian.net/debian wheezy main
and i then i did apt-get update
and finally apt-get install nethogs/wheezy and this works for me. but i didnt ran "apt-get upgrade or dist-upgrade"
however people on forums says it is not a right approach to install updates from wheezy, instead i should use testing and unstable repositories.
@Ralf
nope, this was not a typo. what i mean is, let say we have testing and unstable define in sourcelist, when we run the command apt-get upgrade or apt-get dist-upgrade it changes the OS from stable to sid
what i want to do is, i want some packages that are available in wheezy , Sid and unstable repositories, however they are very old in squeeze.
i also want to keep my system uptodate for any security patchs. with command apt-get upgrade and apt-get dist-upgrade
but if i run above commands while having entries of sid and unstable in sourcelist file it will upgrade my OS to unstable which i do not want.