Function: locate-library

Show the precise file name of Emacs library LIBRARY.
LIBRARY should be a relative file name of the library, a string.
It can omit the suffix (a.k.a. file-name extension) if NOSUFFIX is
nil (which is the default, see below).
This command searches the directories in `load-path' like `M-x load-library'
to find the file that `M-x load-library RET LIBRARY RET' would load.
Optional second arg NOSUFFIX non-nil means don't add suffixes `load-suffixes'
to the specified name LIBRARY.

If the optional third arg PATH is specified, that list of directories
is used instead of `load-path'.

When called from a program, the file name is normally returned as a
string. When run interactively, the argument INTERACTIVE-CALL is t, and the file name is displayed in the echo area.