topic Re: Infinite Loop Question in SAS Programming

Infinite Loop Question

MrBruce — Fri, 11 Nov 2016 20:37:06 GMT

Hi, I have one question on infinite loop. There are two programs, which are shown below.

Why does program A work fine but program B generates infinite loop? thanks.

Program A:

filename qtr1 ('c:\sasuser\month1.dat''c:\sasuser\month2.dat'

'c:\sasuser\month3.dat');

data work.firstqtr;

infile qtr1;

input Flight $ Origin $ Dest $

Date : date9. RevCargo : comma15.;

run;

Program B:

data work.quarter;

do Month = 9, 10, 11;

nextfile="c:\sasuser\month"

!!compress(put(Month,2.)!!".dat",' ');

do until (lastobs);

infile temp filevar=nextfile end=lastobs;

input Flight $ Origin $ Dest $ Date : date9.

RevCargo : comma15.;

output;

end;

run;

Re: Infinite Loop Question

jefreytag — Fri, 11 Nov 2016 21:09:06 GMT

!!compress(put(Month,2.)!!".dat",' ');

Don't you mean

||put(Month,2.)||".dat";

You used exclamation marks. Why do you take the compress function?

Re: Infinite Loop Question

Peter_C — Fri, 11 Nov 2016 21:54:16 GMT

More than one issue:
On windows I think filevar needs to provide a variable holding a single path (and a filename that could hold global chars*? ).
Is the default length of NEXTFILE wide enough to hold the required path\file name ?
I expect you need to reset the value of LASTOBS to zero as it will be retained.

Re: Infinite Loop Question

Tom — Fri, 11 Nov 2016 23:06:00 GMT

Is this a test?

SAS normally stops a data step when it reads past the end of the input data set or text file.

Run this little example to see what I mean.

data _null_;
   put 'BEFORE INPUT' _n_= ;
   input  ;
   put 'AFTER INPUT' _n_ = ;
cards;
1
2
3
;

In your second data step the conditions on your DO loops prevent it from reading past the end of the data. So on iteration 1 it does DO MONTH=9,10,11 and then on iteration 2 it does it again, ad infinitum. Add a STOP statement before the RUN statement.