Hi,
I want to know what is command to know which will tell wheather linux is 32 or 64 bit
If you have gcc installed then compile a trivial "Hello World" program with the "-m64" option, and see if it runs.
You can also try:
uname -m
, but this may only tell you your machine's architecture!
I am not an expert but the "getconf" command may be what you need:
getconf -a | grep FILESIZEBITS
PLEASE NOTE. I am retracting my answer above, because it's stupid. "getconf -a" does give some good info though all by itself, just not what you are looking for. 
uname -a
If its 64-bit linux, it shows x86_64 in the output of the above uname command. Otherwise its 32-bit .
Hope it helps.
Cheers, Bru.
Not true, what happens if it's 64 bit Linux running on DEC-Alpha, Power PC, Itanium, PA-RISC 2.0, ultra-sparc, MIPS, .... etc?