WRKOBJ (Work with Objects) on the AS/400 is a lot like the DIR (directory) command on PC's.

To list all files in library MYLIB that start with "A":

WRKOBJ MYLIB/A* *FILE

To look through all libraries for the file named LOSTFIL:

WRKOBJ *ALL/LOSTFIL *FILE

To look through all libraries in your library list for a program named GLR100:

WRKOBJ GLR100 *PGM