How to report the position of a given character inside a string

/*******************************************************************

  SAS: How to report the position of a given character inside a string

  e.g.: Here have a tring abc_de_fg_ac_ff, we want to get the position

  of '_' in the string. That is, we want to get 4, 7, 10, 13

  In the following two methods are given, the first one using macro. It

  works like this: First, count how many '_' are there in the string.

  Then scan data until find the first '_', report its position. Then from

  this position, scan the rest string for the second one. And so on.

  The second method using data step. Scan the string, when meets '_',

  then report its position. This is easier to understand and code.

*********************************************************************/

******************  Method One   ********************************;

%macro ss(str,dlm);

  %let stt=1;

  %let pos=0;

  %do i=1 %to %sysfunc(count(&str,%str(&dlm))) %by 1;

     %let pos=%eval(%index(%substr(&str,&stt),&dlm)+&stt-1);

        %let stt=%eval(&pos+1);

        %put &pos;

   %end;

%mend ss;

%ss(abc_de_fg_ac_ff,_)

*****************  Method Two **********************************;

data s1;

  str='abc_de_fg_ac_ff';

run;

data s2;

  set s1;

  do i = 1 to length(str);

    if substr(str,i,1)="_" then put  i;

  end;

run;