I saw this piece of code in my project:

%let num = test;
%let x=%sysfunc(trim(&num));

Why could not I write:

%let x= %trim(&num);

Why did I need to use sysfunc?

Under what circumstances can I call a function inside a macro without using sysfunc?


2 Answers 2


Without the sysfunc(), the expression will not be evaluated. You will not be assigning the value of the expression trim(&num) to the macrovariable, but rather the whole expression.

If you want to store the result of an expression, you need to execute that function with sysfunc()


  • $\begingroup$ Thanks. Why we need the % sign in front of sysfunc but not in front of trim? $\endgroup$
    – Victor
    Nov 14, 2015 at 4:00
  • $\begingroup$ The argument to sysfunc is the precise code that sysfunc should execute as though it were not in a macro - so it interprets trim correctly $\endgroup$
    – jamesmf
    Nov 14, 2015 at 15:12

The trim() function is part of the SAS Language. Without the %sysfunc() macro function, trim() can only be used within a data step or in a macro definition that gets called inside of a data step. You can't have it out in open code.

if %trim() existed, which it does not, it would work just fine the way you used it. But, there is no function named %trim() that is defined in the SAS macro language.

Doing what you want without %sysfunc(), would have to go something like:

data _NULL_;
    call symput("x", trim("&num."));

or if you want x to be a data set variable:

%let expr= trim("&num.");

DATA ds;
    x = &expr.;

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