Monday, February 27, 2017

Hack 4.14 Running System Commands from a SAS Program


SAS Programming Professionals,

Did you know that you can execute Windows operating system commands from within a SAS Data step?

You can do this by using the CALL SYSTEM call routine.  Unlike its blunt cousin the X statement, CALL SYSTEM can be executed conditionally within a DATA step.  This makes it much more flexible and useful.  Here is an example:

/* Rename directory on Mondays*/
data _null_;

if weekday(today()) = 2 then do;

      call system("rename c:\temp\mikedir mikedir_old");
      call system("md c:\temp\mikedir");

end;

run;

ods rtf file="c:\temp\mikedir\classlist.rtf";

proc print noobs data=sashelp.class;
title1 "List of Subjects in Weight/Height Study";
run;

ods rtf close;

In the example, the DATA _NULL_ step houses the CALL SYSTEM call routines.  They are only executed when the current day of the week is Monday.  When they are executed, the first CALL SYSTEM sends a command to Windows to rename the MIKEDIR directory to MIKEDIR_OLD.  The second CALL SYSTEM sends a command to Windows to create a new directory named MIKEDIR.  The subsequent PROC PRINT creates an RTF file in the new MIKEDIR directory.

Obviously, the Windows system commands must be syntactically correct for the CALL SYSTEM call routine to work properly.  Here is one of the many online sources for looking up Windows system commands:


The previously mentioned X command executes unconditionally.  That means that if we were to replace both CALL SYSTEM’s with X commands in the program above, they would executed no matter what day of the week it is.  They just barge right in.  That is why I prefer the CALL SYSTEM call routine for shelling out operating system commands from within my SAS programs.

Best of luck in all your SAS endeavors!

---MMMMIIIIKKKKEEEE
(aka Michael A. Raithel)
Author of the new cult classic for computer programmers:  It Only Hurts When I Hit <ENTER>
Print edition:  http://tinyurl.com/z8bzx2e 
Kindle edition: http://tinyurl.com/zypgqa7 

The hack above is an excerpt from the book:  Did You Know That?  Essential Hacks for Clever SAS Programmers

Monday, February 20, 2017

Hack 4.13 Reversing Character Strings with the REVERSE Function


SAS Programming Professionals,

Did you know that: the REVERSE function can be very useful and also a lot of fun to use?

The REVERSE function can be used to return a character string in reverse order.  For instance, consider the following example:

data testit;

x = "SAS";
Y = reverse(x);

put "x= " x;
put "y= " y;

run;

As you can see from the log:

1    data testit;
2
3    x = "SAS";
4    Y = reverse(x);
5
6    put "x= " x;
7    put "y= " y;
8
9    run;

x= SAS
y= SAS

… Y is the exact reverse of X!

A more practical application of this can be found when you need to pluck out the last node in something, such as a full-path file name.  Here is an example from a SAS program that I use to get the name of previously executed SAS programs from the LOGFILE variable in LOGPARSE SAS data sets:

/**********************************/
/* Determine the SAS program name */
/**********************************/
logtemp = reverse(strip(logfile));

r = index(logtemp,"\");

substr(logtemp,r,length(logtemp) - r + 1) = " ";

SASprogram = tranwrd(strip(reverse(logtemp)),"log","sas");


In the example, I know that logfile has the full path name of a SAS log, such as:  "c:\production\fy02\bigprog.log".  If the name of the log is "bigprog.log", then the program that was executed must be "bigprog.sas".  That is what I want to capture in variable SASprogram.

So, the snippet of code first reverses LOGFILE, then looks for the first "/", which was originally the last "/", but is now the first one since the full path has been reversed.  It turns the rest of the contents of LOGTEMP into blanks.  Then, it sets SASprogram equal to the strip-ed, reverse (again) of LOGTEMP while translating "log" into "sas".  Neat, clean, and effective!

Best of luck in all your SAS endeavors!

---MMMMIIIIKKKKEEEE
(aka Michael A. Raithel)
Author of the new cult classic for computer programmers:  It Only Hurts When I Hit <ENTER>
Print edition:  http://tinyurl.com/z8bzx2e 
Kindle edition: http://tinyurl.com/zypgqa7 

The hack above is an excerpt from the book:  Did You Know That?  Essential Hacks for Clever SAS Programmers

Monday, February 13, 2017

Hack 4.12 Renaming Files and Directories from A DATA Step


SAS Programming Professionals,

Did you know that you can rename SAS data sets, SAS catalog entries, as well as OS directories and files in directory-based operating systems from inside of a SAS DATA step? 

The RENAME function lets you do exactly that!  It is great for SAS purists who do not want to use the X command or the CALL SYSTEM routine to “shell out” to the operating system to rename files and/or directories.  And, if you have PROC DATASET phobia, you can use the RENAME function to rename SAS files.

Here is a simple example:

data _null_;

rc = rename('c:\temp\test.pdf', 'c:\temp\old.pdf', 'file');

put "*****************";

put "the return code is: " rc;

put "*****************";

run;

The example above renames “test.pdf” to “old.pdf” in a DATA step.  The nice thing about the RENAME function that differentiates it from the X command or the CALL SYSTEM routine is that you get a return code that you can query to make sure that your rename worked.

Intrigued?  Well, then read more about it in the SAS online documentation on support.sas.com

Best of luck in all your SAS endeavors!


---MMMMIIIIKKKKEEEE
(aka Michael A. Raithel)
Author of the new cult classic for computer programmers:  It Only Hurts When I Hit <ENTER>
Print edition:  http://tinyurl.com/z8bzx2e 
Kindle edition: http://tinyurl.com/zypgqa7 

The hack above is an excerpt from the book:  Did You Know That?  Essential Hacks for Clever SAS Programmers

Monday, February 6, 2017

Hack 4.11 Removing Leading and Trailing Blanks with the STRIP Function


SAS Programming Professionals,

Did you know that there is a function that will effortlessly strip off leading and trailing blanks from a character variable?

The aptly named STRIP function allows you to do just that and is a great replacement for the old TRIM(LEFT(character-variable)) construct many programmers used to use.

Here is an example of using the STRIP function:

data cars;
set  sashelp.cars;

car_statement = "The " || strip(make) ||
                   " " || strip(model)||
              " is a " || strip(type) ||
              ".";

run;

proc print noobs data=cars;                    
      var car_statement;
run;

Which produces, in part:

The Acura MDX is a SUV.
The Acura RSX Type S 2dr is a Sedan.
The Acura TSX 4dr is a Sedan.
The Acura TL 4dr is a Sedan.
The Acura 3.5 RL 4dr is a Sedan.
The Acura 3.5 RL w/Navigation 4dr is a Sedan.
The Acura NSX coupe 2dr manual S is a Sports.
The Audi A4 1.8T 4dr is a Sedan.
The Audi A41.8T convertible 2dr is a Sedan.

In the example, we are constructing variable CAR_STATEMENT by concatenating string constants and concatenating the variables MAKE (13 characters in length), MODEL (40 characters in length) and TYPE (8 characters length).  Without the STRIP function, there would be big gaps in CAR_STATEMENT because many of the MAKEs, MODELs, and TYPEs are not 13, 40, and 8 characters long, respectively.

Best of luck in all your SAS endeavors!

---MMMMIIIIKKKKEEEE
(aka Michael A. Raithel)
Author of the new cult classic for computer programmers:  It Only Hurts When I Hit <ENTER>
Print edition:  http://tinyurl.com/z8bzx2e 
Kindle edition: http://tinyurl.com/zypgqa7 

The hack above is an excerpt from the book:  Did You Know That?  Essential Hacks for Clever SAS Programmers