Using file name from data area for reading IFS file

The idea of this post came from a question I was asked. The questioner had a scenario where the name of an IFS file they needed read is in a data structure. They were unable to work out how to use the value from the data structure as the path name to read of the IFS file.

Let me start using ACS's "Run SQL Scripts", RSS, tool.

Before I can read a file in the IFS I need to create it. I can use the IFS_WRITE SQL procedure to do so:

01 CALL QSYS2.IFS_WRITE('/home/MyDirectory/test.txt', 02 'First line', 03 END_OF_LINE => 'CRLF')

Line 1: Call the IFS_WRITE SQL procedure. Passing to it three parameters first is the file path.

Line 2: Second parameter is the data that will be written to the IFS file.

Line 3: Finally, I need to give what I want the end of line character to be. In this case it is carriage return and line feed.

I can check that the file was created where I expected using the IFS_OBJECT_STATISTICS table function:

01 SELECT PATH_NAME 02 FROM TABLE(QSYS2.IFS_OBJECT_STATISTICS 03 ('/home/RPGPGM/','NO','*STMF'))

Line 1: I only want the path (file) name in my results.

Line 3: I am passing three parameters to the IFS_OBJECT_STATISTICS: directory name, I want no results from any subdirectories, and only stream files.

My result is:

PATH_NAME ----------------------------- /home/MyDirectory/test.txt

I know the file exists, what about its contents? I use the IFS_READ table function to read the file:

01 SELECT * 02 FROM TABLE(QSYS2.IFS_READ( 03 '/home/MyDirectory/test.txt', 04 MAXIMUM_LINE_LENGTH => 50))

Line 3: This is the path of the file I want to read.

Line 4: The maximum record length of this file is 50 characters, which is bigger than the string I wrote to the file but that does not cause an problem.

The results show that I what I expected was written to the file.

LINE_NUMBER LINE ----------- -------------------- 1 First line

I now need a data area, which I created with the following CL statement:

01 CRTDTAARA DTAARA(MYLIB/TESTDA) 02 TYPE(*CHAR) LEN(100) 03 VALUE('home/MyDirectory/test.txt')

I can retrieve the contents of the data structure using the DATA_AREA_INFO table function:

01 SELECT DATA_AREA_VALUE 02 FROM TABLE(QSYS2.DATA_AREA_INFO 03 ('TESTDA','MYLIB'))

The result confirms that I have the information I desire in the data area:

DATA_AREA_VALUE -------------------------------- /home/MyDirectory/test.txt

I need to thank Christian for the code below. He corrected my original SQL statement to retrieve the value from the data area and use it as the path name in IFS_READ:

01 SELECT * 02 FROM TABLE(QSYS2.IFS_READ( 03 (SELECT TRIM(DATA_AREA_VALUE) 04 FROM TABLE(QSYS2.DATA_AREA_INFO 05 ('TESTDA','MYLIB'))), 06 MAXIMUM_LINE_LENGTH => 50))

Line 3: The trim of the data area column is essential for the path name to be valid.

The result from the amended statement is:

LINE_NUMBER LINE ------------ ------------- 1 First line

Let me switch from RSS to RPG, and explain how I can take the above statements and accomplished this scenario.

Here is the code for my RPG program:

01 **free 02 dcl-s Line varchar(50) ; // Create/write file in IFS 03 exec sql CALL QSYS2.IFS_WRITE('/home/MyDirectory/test.txt', 04 'First line', 05 END_OF_LINE => 'CRLF') ; // Read file in IFS 06 exec sql SELECT LINE INTO :Line 07 FROM TABLE(QSYS2.IFS_READ( 08 (SELECT TRIM(DATA_AREA_VALUE) 09 FROM TABLE(QSYS2.DATA_AREA_INFO 10 ('TESTDA','RPGPGM1'))), 11 MAXIMUM_LINE_LENGTH => 50)) 12 LIMIT 1 ; 13 dsply SQLCOD ; 14 dsply Line ; 15 *inlr = *on ;

Line 2: I am defining the variable that will be used to retrieve the contents of the IFS file.

Lines 3 – 5: I am creating the file in the IFS, as I did above at the beginning of this post.

Lines 6 – 12: This is almost the same as the IFS_READ statement below. The only difference is on line 12.

Line 12: As the IFS_READ could return more than one row, I need to limit the results to one.

Line 13: If the IFS_READ failed for any reason the SQL code will not be zero.

Line 14: I want to display the value I retrieved from the IFS file.

After compiling the program I then called it, and the following was displayed:

DSPLY 0 DSPLY First line

The first DSPLY is zero, which shows that there were no issues with the IFS_READ.

The second is the contents of the file in the IFS.

 

This article was written for IBM i 7.5, and should work for some earlier releases too.