%let ans=%ds_check(dsn, lib=WORK);

Trim a list of string elements to keep only those that actually define existing datasets in a given library.

%ds_check(dsn, _dslst_=, lib=WORK);

dsn : a dataset reference;
lib : (option) name of the input library; by default: empty, i.e. WORK is used.

ans : (option) the error code of the test, i.e.:
- -1 when the library does not exist,
- 0 if the dataset exists,
- 1 (error: "dsn does not exist") otherwise.
should not be used contemporaneously with the option _dslst_ below;
_dslst_ : (option) name of the macro variable used to store the elements from var that actually define existing variables/fields in dsn; incompatible with returned result ans above.

Let us consider a non-empty dataset:

%_dstest0;

%let ans=%ds_check(_dstest0, lib=WORK);

returns ans=0. Let us then generate some datasets in WORKing directory:

%_dstest1;
%_dstest2;
%_dstest5;

we can then also use the macro to retrieve those elements in a given list that actually correspond to existing datasets in WORK:

%let ds=;
%let ids= _dstest1 dummy1 _dstest2 dummy2 _dstest5;
%ds_check(&ids, _dslst_=ds, lib=WORK);

returns ods=_dstest1 _dstest2 _dstest5.

Run macro %_example_ds_check for examples.

As mentioned above, two types of outputs are possible: either the answer ans to the test when a result shall be returned (and _dslst_ is not passed), or an updated list of acceptable datasets (when _dslst_ is passed). The former case is useful when testing a single dataset existence in a library, the latter for triming a list of actual datasets. Contemporaneous use is impossible.
In short, the error code returned (when _dslst_ is not passed) is the evaluation of:

1 - %sysfunc(exist(&lib..&dsn, data));

The order of the variables in the output list matches that in the input list dsn.
When none of the string elements in dsn matches a dataset in lib, an empty list is set.