# Check this environment variable with echo $PATH. This problem is usually a matter of the environment variable PATH being incorrect.
[root@localhost ~]# echo $PATH

# Use the whereis command to see, where this command is located.
[root@localhost ~]# whereis man

# Use that address directly, or add that path to PATH. There are two ways to add the PATH environment variable.
# Method 1: PATH disappears when the terminal is closed.
[root@localhost ~]# export PATH=/usr/local/webserver/mysql/bin:$PATH
# Method 2: Change PATH by editing /etc/profile, you can also change .bashrc in your home directory (i.e. ~/.bashrc).
[root@localhost ~]# vim /etc/profile
[root@localhost ~]# export PATH="/usr/local/webserver/mysql/bin:$PATH"
[root@localhost ~]# source /etc/profile