Edit: What I mean by context is:
* Are you looping in a macro?
* Do you need to create multiple files from a single data step?
* Can you supply the relevant code excerpts?
* Etc...
You still haven't added context, so this will be my last guess:
* get path to work directory ;
%let work=%sysfunc(pathname(work));
* create some dummy files ;
data _null_;
length file $200;
do i=1 to 5;
file=cats("&work","\foo",i,".txt");
file foo filevar=file;
put 'x';
end;
run;
* get list of files ;
%dirlist(dir=&work, filter=basename=:'foo' and ext='txt')
%let num=%nobs(dirlist);
* create more files ;
data _null_;
length file $200;
retain num #
do i=1 to 5;
num+1;
file=cats("&work","\foo",num,".txt");
file foo filevar=file;
put 'x';
end;
run;
https://github.com/scottbass/SAS/blob/master/Macro/dirlist.sas
https://github.com/scottbass/SAS/blob/master/Macro/nobs.sas
Adjust to suit. For example, you might need to parse dirlist --> filename to get max suffix.
Another approach is to just start a counter=1, use the fileexist function to check for existence of foo<counter>.txt, and increment counter until file does not exist. This should perform ok unless you had thousands of foo<counter>.txt files in your output directory.
Good luck!
Please post your question as a self-contained data step in the form of "have" (source) and "want" (desired results).
I won't contribute to your post if I can't cut-and-paste your syntactically correct code into SAS.
