Macro XSET (from Fraktal SAS Programming)

What it does

This SAS Macro transfers the environment from the particular operating system to SAS Macro variables.

Code executed	Function performed
%MACRO xset(xvar);	Start Macro definition with name and positional parameter xvar
filename path pipe "set" lrecl = 2048;	Open source for text data of type pipe pointing to OS command
data ecotope / view = ecotope;
length xvar $256 xval $1024;	Declare variables xvar and xval by length in bytes
infile path dlm = '=';	Utilize data stream from data source path
input xvar $ xval $;	Define structure of data stream path with variables xvar and xval
xvar = upcase(translate(xvar,'_','(-)'));	Remove unwanted characters from variable xvar
%IF %LENGTH(&XVAR.) != 0 %THEN %DO;	Specify condition on macro parameter xvar for using code segment
if trim(xvar) = "%UPCASE(&XVAR.)";	Conditionally executed code
%END;	End condition on macro parameter xvar
run;
proc sql noprint;
select xvar
into :xvar_l separated by ' '
from ecotope
;
quit;
%GLOBAL &XVAR_L.;
data _NULL_;	Start datastep run group
set ecotope;
call symput(compress(xvar),compress(xval));	Transfer variable values to symbol table
run;	End data step run group
filename path clear;	Close source for text data
%MEND xset;	End Macro definition with name

The Macro first defines the OS command "SET" as text data source (SAS file reference) of type "PIPE" that delivers a dynamic two-column matrix with delimiter "=" upon reference to the fileref.
This fileref is then used to dynamically "populate" a "data step view" that serves as data source for subsequent processing.
From the left side of the matrix accessed the macro obtains the names of the OS environment variables and stores them as blank-separated list into a macro variable for use later on.
Finally a data step with name "_NULL_" is used to write the two-variable dataset delivered by the data step view into the global symbol table.