Section 3.7: FILENAME -- Specify an External File Name

Rather than write the name of an external file in quotes as part of the INFILE 
statement in the DATA step, you can enter the FILENAME statement:

FILENAME <fileref> 'c:\project\data\myfile.dat';

For example,

OPTIONS formdlim=' ' nocenter ls=78 ps=55;
FILENAME fish "c:\project\data\fish.dat";

The word fish, defined in the FILENAME statement, appears in the INFILE statement 
in the next DATA step.

DATA fish;
INFILE fish missover lrecl=350 firstobs=4;
INPUT id $ a b c x y z;
....
RUN;


With a FILENAME specification, it is possible to compute how to write data to an 
external text file. Unlike delarative statements, FILE is an executable statement 
which can be invoked to choose which file to write to based on a condition. 
Here's an example:

FILENAME even 'c:\t\even.dat';
FILENAME odd  'c:\t\odd.dat';

DATA _null_;
DO n = 1 to 5, 7, 8, 11; /* 1 3 5 7 11 are written to odd.dat
                           2 4 8 are written to even.dat*/
    if mod(n,2) = 1 then FILE odd ;
    else                 FILE even;
PUT n;
END;
run;