/*
In programming statistical routines in SAS, one of the things you need as a programmer
is to grab the names of the variables in the dataset. SAS has some special functions
to do this that require using a do loop that looks at each column from left to write.
Once you loop through the names, you can write them out to a file. In this example, 
we simply write the names of the variables to a text file: c:\names.txt. Although
you could get the variable names other ways (proc contents, etc.), this serves as
a good illustration of looping and the special sysfunctions of SAS.
*/
*First we read in a test data set for you;
data mydata;
 input Y VAR1 VAR2 VAR3;
cards;
1	10	33	4
0	20	21	3
1	30	59	2
1	20	76	1
0	30	24	3
0	20	22	2
1	10	28	2
1	10	49	2
0	30	76	2
1	20	59	2
;


%macro getnames(dsn,myfile);
*reads data into another dataset for illustration purposes;
*dsn is the name of the dataset you pass in the macro;
*The 2nd thing you pass is what you want to call the output file;
data testdata;
 set &dsn;
 file &myfile;
run;

*The following line useful whenever you run a macro because it prints out all the steps.;
OPTIONS NOTES SOURCE SOURCE2 MPRINT MLOGIC MERROR SYMBOLGEN;

   %let dsid=%sysfunc(open(&dsn));
   %let cnt=(%sysfunc(attrn(&dsid,nvars)));
   %do i = 1 %to &cnt;
     %let myname=%sysfunc(varname(&dsid,&i));
    data _null_; /*_null_ means you only read the file, you don't save it */
         set &dsn end=last;
         file &myfile mod;
   if last then put "&myname";
   run;
   %end;
   %let rc=%sysfunc(close(&dsid));
%mend getnames;

%getnames(mydata,'c:\names.txt');