How to Handle Strings in SAS - sas

Question

Why is it that sometimes we need to wrap the string value in single quotes, sometimes double quotes, sometimes no quotes? This is extremely frustrating when I have to go from one proc to another, especially if it involves changing a file name or url dynamically. What is the logic behind this hideous monstrosity?
%let Name01 = John Smith;
%let Name02 = 'John Smith';
%let Name03 = "John Smith";
All three work.
%let Folder = /97network/read/Regions/Northeast/;
%let FileName = SalesTarget.xlsx;
proc import
datafile = "&Folder.&FileName."
dbms = xlsx
out = SymList replace;
sheet="Sheet1";
run;
Here, &Folder.&FileName. must be in double quotes.
filename OutFile "/06specialty/ATam/AMZN.csv";
proc http url = &urlAddress. method = "get" out = OutFile;
run;
Finally, if I want to download stock prices from Yahoo Finance, url = may take the address in single quotes, or &urlAddress. in no quotes, but you cannot use double quotes. OutFile can be in single or double quotes, but not no quotes. Then in the out = clause, you have OutFile, not &OutFile.

Answer 1

SAS strings are very simple. They are enclosed in either single or double quote characters.
'Hello there'
"Good-bye"
If the enclosing character appears in the string it needs to be doubled up.
'I don''t know'
To your first example it is probably your operating system that is allowing filenames to include optional quotes. On Windows and Linux the qutoes can even be required in some situations when the path includes spaces or other characters that the command shell would normally interpret as delimiters in the command line.
Adding macro logic into the program is probably a large part of your confusion. First figure out what code works for the commands you are using and then you can try to generate that code using the macro processor.
Once you introduce macro logic you need to pay attention to whether your strings are using single or double quotes. There is big difference between how macro logic interacts with single and double quote characters. Strings that are bounded by single quote characters are ignored by the macro processors. So the macro trigger characters & and % are treated as normal characters. But strings that are bounded by double quote characters will be processed.
Your second example adds the complexity of working with URL syntax. URL strings use the & character for its own purpose so you need to take care to understand how SAS is going to see the code you type and whether or not the macro processor will attempt to interpret it to insure the desired string needed for the URL will be created.

Answer 2

SAS has 50 years of history and a lot of the code is legacy. SAS is backwards compatible. You can still run code 30 years old with no issues. There are lots of oddities, such as quotes, that are there...and will always be there. SAS is kind of a conglomeration of ~300 languages (every proc is unique plus multiple meta-languages).
Since SAS will never change, best to just ignore the oddities.
One other thing. SAS runs on lots of O/Ss so every nuance there has to be accommodated in a mostly neutral way.