How to check dataset exist in libraries and run the following code

[SASuserlot]

I have like 30 libraries ( created by another macro as an initial setup). I am checking if my interested dataset exists in the library. How can I do this? The purpose of this code is, if this dataset exists then I want to run another macro/data step. I created the sample. Thank you for your suggestions, and sorry if any mistakes in my sample; I will correct them as I get suggestions.

** Just created the libraries, for example;

libname s1 'D:\New folder';
libname s2 'D:\New folder 1';

data s1.chk;
x='y';
run;


** if dataset 'chk' in 's1' or 's2' library then the 
the following code has to run; otherwise need a note
'No dataset exists';


*&lib is the library where the dataset existed;

data chk_&lib;
set &lib.chk;
flag ='Y';
run;

[Kurt_Bremser]

%if %sysfunc(exist(&lib..chk)) %then %do;

/* conditional code */

%end;

[SASuserlot]

Thank you @Kurt_Bremser . This code works. However, I have an extension question. I  have 30 libraries. Is there anyway &lib' created automatically by using like dictionary. tables or vcolumn ? otherwise, I have to run a macro for each library.

[andreas_lds]

What should happen if the dataset exists in both libraries?

[SASuserlot]

if data set is present in both libraries, then it should execute the following code and create the chk_s1, chk_s2 datasets.

data chk_&lib;
set &lib.chk;
flag ='Y';
run;