Simply add echo $i; before or after the command
pons@linpons:~/VanitySearch$ for i in `more tst.txt`; do echo $i;./VanitySearch -cp $i | grep Addr | grep P2PKH | awk '{ print $3 }'; done
5B3F38AF935A3640D158E871CE6E9666DB862636383386EE510F18CCC3BD72EB
12csaq6uhAtyhzUN8N4akVpat7GP6wB3ea
5B3F38AF935A3640D158E871CE6E9666DB862636383386EE510F18CCC3BD72EC
1PGVt2mWHgbULrx9pjWDPc2EKp2LWLT4fd
5B3F38AF935A3640D158E871CE6E9666DB862636383386EE510F18CCC3BD72ED
1DVjd5oZqCCYywtgL7FLbT3ZX4FFJK5nwc
or
pons@linpons:~/VanitySearch$ for i in `more tst.txt`; do ./VanitySearch -cp $i | grep Addr | grep P2PKH | awk '{ print $3 }';echo $i; done
12csaq6uhAtyhzUN8N4akVpat7GP6wB3ea
5B3F38AF935A3640D158E871CE6E9666DB862636383386EE510F18CCC3BD72EB
1PGVt2mWHgbULrx9pjWDPc2EKp2LWLT4fd
5B3F38AF935A3640D158E871CE6E9666DB862636383386EE510F18CCC3BD72EC
1DVjd5oZqCCYywtgL7FLbT3ZX4FFJK5nwc
5B3F38AF935A3640D158E871CE6E9666DB862636383386EE510F18CCC3BD72ED