The SOURCEROOT function, in combination with FILEPATH, allows a program to locate other files within a routine source file's related directory tree.

For example, an IDL routine file named C:\myapp\abc.pro calls SOURCEROOT as in

    PRO ABC
    PRINT, SOURCEROOT()
    END
 

the resulting output will be the string "C:\myapp".

If data associated with the application are in C:\myapp\mydata, a data file in this directory can be located via

    IDL> datafile = FilePath('data.dat',$
    IDL>   ROOT=SourceRoot(), $
    IDL>   SUBDIR=['data'])
 

The programmer can distribute the application to another user who may install the original directory tree into "D:\app". No code modifications would be required for this user to successfully locate the data.dat file.

If the routine ABC were compiled and saved to an IDL SAVE file and distributed, the SOURCEROOT function will return the path to the SAVE file instead.