[linux] Shell - How to find directory of some command?

I know that when you are on shell, the only commands that can be used are the ones that can be found on some directory set on PATH. Even I don't know how to see what dirs are on my PATH variable (and this is another good question that could be answered), what I'd like to know is:

I come to shell and write:

$ lshw

I want to know a command on shell that can tell me WHERE this command is located. In other words, where this "executable file" is located?

Something like:

$ location lshw
/usr/bin

Anyone?

An alternative to type -a is command -V

Since most of the times I am interested in the first result only, I also pipe from head. This way the screen will not flood with code in case of a bash function.

command -V lshw | head -n1

PATH is an environment variable, and can be displayed with the echo command:

echo $PATH

It's a list of paths separated by the colon character ':'

The which command tells you which file gets executed when you run a command:

which lshw

sometimes what you get is a path to a symlink; if you want to trace that link to where the actual executable lives, you can use readlink and feed it the output of which:

readlink -f $(which lshw)

The -f parameter instructs readlink to keep following the symlink recursively.

Here's an example from my machine:

$ which firefox
/usr/bin/firefox

$ readlink -f $(which firefox)
/usr/lib/firefox-3.6.3/firefox.sh

In the TENEX C Shell, tcsh, one can list a command's location(s), or if it is a built-in command, using the where command e.g.:

tcsh% where python
/usr/local/bin/python
/usr/bin/python

tcsh% where cd
cd is a shell built-in
/usr/bin/cd

~$ echo $PATH
/home/jack/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
~$ whereis lshw
lshw: /usr/bin/lshw /usr/share/man/man1/lshw.1.gz

Like this:

which lshw

To see all of the commands that match in your path:

which -a lshw 

The Korn shell, ksh, offers the whence built-in, which identifies other shell built-ins, macros, etc. The which command is more portable, however.