How to detect CPU architecture/bitmode (32-bit or 64-bit) for Linux ?

cat /proc/cpuinfo | grep flags

you will find one of them with name "tm(transparent mode)" or
"rm(real mode)" or "lm(long mode)"

1. rm tells ,it is a 16 bit processor
2. tm tells, it is a 32 bit processor
3. lm tells, it is a 64 bit processor