bash-4.1# which bin/hadoop
/usr/local/hadoop-2.7.0/bin/hadoop

bash-4.1# ls /bin/hadoop
ls: cannot access /bin/hadoop: No such file or directory
bash-4.1#

bash-4.1# which hadoop
which: no hadoop in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/java/default/bin)
bash-4.1#