mf__getuniquefileref_8sas_source.html

/**

  @file

  @brief Assigns and returns an unused fileref

  @details  Using the native approach for assigning filerefs fails as some

  procedures (such as proc http) do not recognise the temporary names (starting

  with a hash), returning a message such as:


  > ERROR 22-322: Expecting a name.


  This macro works by attempting a random fileref (with a prefix), seeing if it

  is already assigned, and if not - returning the fileref.


  If your process can accept filerefs with the hash (#) prefix, then set

  `prefix=0` to revert to the native approach - which is significantly faster

  when there are a lot of filerefs in a session.


  Use as follows:


      %let fileref1=%mf_getuniquefileref();

      %let fileref2=%mf_getuniquefileref(prefix=0);

      %put &fileref1 &fileref2;


  which returns filerefs similar to:


> _7432233 #LN00070


  @param [in] prefix= (_) first part of fileref. Remember that filerefs can only

    be 8 characters, so a 7 letter prefix would mean `maxtries` should be 10.

    if using zero (0) as the prefix, a native assignment is used.

  @param [in] maxtries= (1000) the last part of the libref. Must be an integer.

  @param [in] lrecl= (32767) Provide a default lrecl with which to initialise

    the generated fileref.


  @version 9.2

  @author Allan Bowe

**/


%macro mf_getuniquefileref(prefix=_,maxtries=1000,lrecl=32767);

  %local rc fname;

  %if &prefix=0 %then %do;

    %let rc=%sysfunc(filename(fname,,temp,lrecl=&lrecl));

    %if &rc %then %put %sysfunc(sysmsg());

    &fname

  %end;

  %else %do;

    %local x len;

    %let len=%eval(8-%length(&prefix));

    %let x=0;

    %do x=0 %to &maxtries;

      %let fname=&prefix%substr(%sysfunc(ranuni(0)),3,&len);

      %if %sysfunc(fileref(&fname)) > 0 %then %do;

        %let rc=%sysfunc(filename(fname,,temp,lrecl=&lrecl));

        %if &rc %then %put %sysfunc(sysmsg());

        &fname

        %return;

      %end;

    %end;

    %put unable to find available fileref after &maxtries attempts;

  %end;

%mend mf_getuniquefileref;