Thanks to Jack Hamilton, Peter Crawford, and Babatunde Ashiru for pointing out that I needed to invoke the FWRITE function following the FPUT function. Jack won the race though (his post timestamped all of 17 minutes after mine); as people keep saying, SAS-L is marvelous.

Peter asked "why mixing scl and regular datastep file handling improves anything".

I turned to SCL because I want to change external file references *during* DATA step execution. My first choice was the FILEVAR option, but (a) it only permits changing the "physical" file name and I also want to change some other things (options) coded on the FILENAME statement and (b) it does not seem to work for the particular devices/methods I am using.

I can use straight SCL rather than mixing, but I suspected that performance would suffer. I experimented by generating a million records both ways (code shown below). I ran this repeatedly and the times varied on my desktop system, but the SCL always took roughly 35 percent longer. I can live with that. My initial tests suggest that mixing can work, but if it doesn't I'll just use SCL to do the I-O.

Here are the two data steps. The first one also serves as an example of the sequence of function calls which will open a file, write to it, and close it.

data _null_; * SCL; rcode1 = filename('scltime','scltime.txt'); file_id = fopen('scltime','O'); do i = 1 to 1000000; rcode2 = fput(file_id ,put(i,z7.)); rcode3 = fwrite(file_id); end; rcode4 = fclose(file_id ); rcode5 = filename('scltime',''); run;

data _null_; * Traditional input-output; file 'tiotime.txt'; do i = 1 to 1000000; put i z7.; end; run;