How can I read the USER list?

The following code will traverse the USER list.

BEG READ 0SA USER      HOLD 0      KEY IS
SET      0SA USER ID            =  0SA USER ID
SET      0SA USER NAM           =  0SA USER NAM
END READ 0SA USER

When you enter the BEG READ into the ILF editor, it will give you a message "WARNING - File not found", which you can ignore (option 88).

Be very careful what you do with these techniques, as THEY ARE NOT SUPPORTED BY APPX SOFTWARE, and may change without notice.