When running a command from terminal, how can I know the full path of the command?

Assuming I'm writing in Terminal: 'ctags', how can I know the full path of the command 'ctags?

$ type ctags
ctags is /usr/bin/ctags
$ type -p ctags
/usr/bin/ctags

The second form is useful for doing things like

$ file $(type -p ctags)
$ ls -l $(type -p ctags) 

and is often aliased to which.

If you don't want to rely on bash functionality and prefer an external command, /usr/bin/whereis serves a similar purpose:

The whereis utility checks the standard binary directories for the specified programs, printing out the paths of any it finds.

Because whereis doesn't use $PATH but rather the result of sysctl user.cs_path it may lead to different results.

Type the command as a parameter, for e.g. to find location of tar

ls -l $(which tar)

which in my case returns

lrwxr-xr-x  1 root  wheel  6 Jul 26  2012 /usr/bin/tar -> bsdtar