If for any reason you need to find where in the disk a command, you may use
which this command will search on the PATH and display the directory where the command is located.
You may also look for a list of commands instead of a simple command, lets see some examples: <p class="codigo">which ls</p>
The output is:
Now if you run:
This is the output in my PC, where I have opera installed.
But, you can also run which to look for a list of commands as I said before.
which ls opera
This might be the output:
For more information, see the man pages.