Difference between LET/SET

[#1]

Hello !

I always confuse myself about using LET or SET or none of them.

Say that I want to create a NEW variable ? Do I use LET or SET ?

What about assigning a value to a variable ? Do I use LET/SET or nothing ?

Thanks !

[Anonymous]

It is very simple:

using SET you are adding string value to a variable
SET Variable1='4+5';
variable value is '4+5'

using LET you are adding an expression result to a variable
LET Variable1=4+5;
variable value is 9

Rgds,
Artjoms

[#3]

Hi Jabalite ,

The set statement is used for defining script variables. These can be used for substituting strings, paths, drives, etc.

The let statement, in opposition to the set statement, evaluates the expression on the right side of the ' =' before it is assigned to the macro variable.

Set x=3+4;

Let y=3+4

z=$(y)+1;

$(x) will be evaluated as ' 3+4 '

$(y) will be evaluated as ' 7 '

$(z) will be evaluated as ' 8 '

Regards,

Poorva

[#4]

Thanks to you all !

Now I understand :

SET is like a # DEFINE in C

and

LET is the typical assignment operator !

Thanks !

[#5]

Ops...

I'm confused again...

I have a situation here where several CSV files are available on a folder. I want to pick the LAST file name on the path. Cause the file path has the YEAR/MONTH on it's composition. An example of file name is 'FPCDA_200911.CSV' where 200911 is the year/month of the file.

So I need to pick the last YEAR/MONTH file available on that folder.

Here's how I coded it :

LET LASTFILE='';

FOR EACH AFILENAME IN FILELIST R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\*.QVD;
 IF '$(AFILENAME)' > '$(LASTFILE)' THEN
 SET LASTFILE=$(AFILENAME);
 END IF
NEXT

LET FILENAMETOBEREAD=$(LASTFILE);

LOAD
...
FROM $(FILENAMETOBEREAD)

But now I'm not sure if this is the appropriate coding for that ..

Can you help me ?

Once more, thank you !

[#6]

Ops...

I'm confused again...

I have a situation here where several CSV files are available on a folder. I want to pick the LAST file name on the path. Cause the file path has the YEAR/MONTH on it's composition. An example of file name is 'FPCDA_200911.CSV' where 200911 is the year/month of the file.

So I need to pick the last YEAR/MONTH file available on that folder.

Here's how I coded it :

LET LASTFILE='';

FOR EACH AFILENAME IN FILELIST R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\*.QVD;
 IF '$(AFILENAME)' > '$(LASTFILE)' THEN
 SET LASTFILE=$(AFILENAME);
 END IF
NEXT

LET FILENAMETOBEREAD=$(LASTFILE);

LOAD
...
FROM $(FILENAMETOBEREAD)

But now I'm not sure if this is the appropriate coding for that ..

Can you help me ?

Once more, thank you !

[#7]

I'm still confused....

I don't understand why the code below does not work.

Say that I have a folder with several CSV files on it. The file names are comprised of a prefix plus YEAR/MONTH of the file. Like this file names list :

R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200901.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200902.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200903.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200904.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200905.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200906.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200907.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200908.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200909.CSV
R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\FPCDA_200910.CSV

Notice that '200910' is the YEAR/MONTH of the file.

I need to discover the last YEAR/MONTH file on that folder, to read THAT file.

I coded like this :

LET LASTFILE='';

FOR EACH FILE_NAME IN FILELIST R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\*.QVD;
 IF '$(FILE_NAME)' > '$(LASTFILE)' THEN
 LET LASTFILE=$(FILE_NAME);
 END IF
NEXT

LOAD
...
FROM $(LASTFILE)

I dont know why that code does not work...

Thanks !

[Anonymous]

What kind of files are you loading then? 'Cause in directory you have CSV file, but in FOR EACH statement you mentioned QVD extension.
First of all it is very important to follow the sintax, then everything will be fine

Secondly, it is hard to compare strings, that's why I involved one more variable var2 which value is number (year and month)

This script is working (tested):

LET var1=0;

For Each File in Filelist ('R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\*.CSV')
 LET var2 = Left(Right('$(File)',10),6);
 If '$(var2)' > '$(var1)' Then
 SET LastFile = '$(File)';
 LET var1 = '$(var2)';
 End If
Next File

Load *
FROM [$(LastFile)] (ansi, txt, delimiter is ',', embedded labels, msq); // for CSV files
//FROM [$(LastFile)] (qvd); // for QVD files

Case you have QVD files change CSV extension to QVD in "For Each..." line, uncomment From line for QVD and comment line for CSV.

Good luck!

Rgds,
Artjoms

[#9]

Ops ! Sorry !

The fact is that we have an Unisys mainframe and all tables are downloaded from it as CSV. Right after downloading them, I convert them all to QVD. So, on that folder I have a QVD for each CSV file. That's automatic. Whenever I extract a table from the mainframe this thing happens. I've built this infrastructure already.

As for the string comparison, I understand that it is boring.

However, I wanna a more "generic" code cause there are several filename formats. Sometimes it's YYYYMM, others are YYYYMMDD and yet on others we have simply a number (counter) amongst the file name.

But I'm STILL confused with SET/LET !!!!!!!!!!!!!!!!

You used

SET LASTFILE=

Why not 'LET' in this case as well ?

Funny, I'm a skilled programmer ! Never got messed up by such a silly thing !

But thanks again !

[Anonymous]

I used SET LastFile, 'cause I need to assign a simple string to a variable value ('$(File) - is a string)

Probably you have to compare file creation date and time to get latest (last) file. For this QV has a function FileTime

Try this...

Let var1=0;

For Each File in Filelist ('R:\USR\CPD\PRO\GT\01\EB\DADOS\FP\FPCDA\*.QVD')
 If FileTime('$(File)') > '$(var1)' Then
 SET LastFile = '$(File)';
 LET var1=FileTime('$(File)');
 End If
Next File

Load *
FROM [$(LastFile)] (qvd);