1. Working with the IFS from RPG.
What is the IFS?
What is a Stream File?
Why would I want to do that with RPG?
Integrated Files System – anything not related in the traditional iSeries world i.e. qsys.lib
Could be things on the I, could be things on other servers that follow the PC or Unix world of file structure
Every Object is a stream file in that world. Program, data files, text files

2. File Systems Available on the i
/QSYS.LIB – Traditional File Ssystem
/QDLS – Document Library System – MS Dos like
/QOpenSys – The Open Systems File System
/ - Root file system – Windows
Other File systems i.e. /QNTC any other server connected to your lan
QDLS – everything must fit the 8.3 naming convention – no spaces
/QNTC same as \\Server\ in the PC world
WrkFlr – gets you in the structure starting at /QDSL

3. Traits of these “non” traditional file systems
Folder – Subfolder and a hierarchy of folders or directories
Files are all stream files
Not fixed length
Everything is a stream file – Programs, data, pictures,
Even folders or directories are just another stream file
No defined fields
Stream of Characters
XML, comma separated, JSON, Text
Another reason to not call DB2 files but call them tables.

4. IBM – Unix Type API to access the IFS
Written for C Programmers
C style for data types – c type strings
Return type typically integer (10i 0)
Return value indicates if the call was successful
-1 error
Anything else success
Can be called as a function in RPG
Scot Klements tools are are RPG entry point to access the IFS,
Unix type API’s to work with IFS,
Unix / C style. These API are written to be accessed from C., or a Unix Environment
What Scott has provided is RPG code – nothing really executable but that allows us access to these API’s

5. IFSIO_H Include source member from Scott Klement
Includes constants, data structures and prototypes
Access to the API’s for working with stream files
Lots of prototypes – we are going to look at open, write and read.
Many more functions available – we could spend all day.
85 page tutorial that I will have a link to at the end.

6. ErrNo_H Mostly error number constants – descriptive names
Several prototypes all dealing with errors.
Separate because these values are also used in other areas besides the IFS API’s

7. Open D open PR 10I 0 ExtProc('open')
D filename * value options(*string)
D openflags I 0 value
D mode U 0 value options(*nopass)
D ccsid U 0 value options(*nopass)
D txtcreatid U 0 value options(*nopass)
Mode is access rights

8. D* Flags for use in open() D*
D* More than one can be used -- add them together.
D* Reading Only
D O_RDONLY C
D* Writing Only
D O_WRONLY C
D* Reading & Writing
D O_RDWR C
D* Create File if not exist
D O_CREAT C
D* Exclusively create
D O_EXCL C
D* Assign a CCSID
D O_CCSID C
D* Truncate File to 0 bytes
D O_TRUNC C
D* Append to File
D O_APPEND C
D* Synchronous write
D O_SYNC C
D* Sync write, data only
D O_DSYNC C
D* Sync read
D O_RSYNC C
D* No controlling terminal
D O_NOCTTY C
D* Share with readers only
D O_SHARE_RDONLY C
D* Share with writers only
D O_SHARE_WRONLY C
D* Share with read & write
D O_SHARE_RDWR C
D* Share with nobody.
D O_SHARE_NONE C
D* Assign a code page
D O_CODEPAGE C
D* Open in text-mode
D O_TEXTDATA C
D* Allow text translation

9. D* No controlling terminal D O_NOCTTY C 32768
D* Append to File
D O_APPEND C
D* Synchronous write
D O_SYNC C
D* Sync write, data only
D O_DSYNC C
D* Sync read
D O_RSYNC C
D* No controlling terminal
D O_NOCTTY C
D* Share with readers only
D O_SHARE_RDONLY C
D* Share with writers only
D O_SHARE_WRONLY C
D* Share with read & write
D O_SHARE_RDWR C
D* Share with nobody.
D O_SHARE_NONE C
D* Assign a code page
D O_CODEPAGE C
D* Open in text-mode
D O_TEXTDATA C
D* Allow text translation

10. D* Share with writers only D O_SHARE_WRONLY C 131072
D* Share with read & write
D O_SHARE_RDWR C
D* Share with nobody.
D O_SHARE_NONE C
D* Assign a code page
D O_CODEPAGE C
D* Open in text-mode
D O_TEXTDATA C
D* Allow text translation

11. P*--------------------------------------------------
P* Procedure name: openXML
P* Purpose: Open the file and returns FD
P* Returns: File Description
P* Parameter: fileName => The file that is to be created
P openXML B export
D openXML PI I 0
D fileName A
D* Local fields
D retField S I 0
D Error s p 0
// Error Handling parameters
d Message s a

12. FullFileName = FileName; retField = -1;
d ErrorB ds qualified
/FREE
ErrorFound = *OFF;
FullFileName = FileName;
retField = -1;
retField = open(%trim(fileName) :
O_CREAT+O_TRUNC+O_WRONLY+O_CCSID + O_TEXTDATA + O_TEXT_CREAT : S_IRWXU + S_IRWXG + S_IRWXO :
819 :
0 );
if RetField = -1;
Error = ErrNo();
ErrorFound = *ON;
Qp0zLprintf('--> Error Opening File: %s'+LF:%editc(Error:'X'));
Qp0zLprintf(' File Name: %s' + LF:%Trim(FullFileName));
Return value – flag for other calls
-1 error
In order to call errno or strerror, you must bind to the
* QC2LE binding directory. See ERRNO_H for the definitions
* used to access errno. *

13. D*--------------------------------------------------------------------
D* Read From a File D*
D* ssize_t read(int handle, void *buffer, size_t bytes);
D read PR I 0 ExtProc('read')
D handle i 0 value
D buffer * value
D bytes U 0 value

14. D*--------------------------------------------------------------------
D* Read From a File D*
D* ssize_t read(int handle, void *buffer, size_t bytes);
D read PR I 0 ExtProc('read')
D handle i 0 value
D buffer * value
D bytes U 0 value

15. D*--------------------------------------------------------------------
D* Close a file D*
D* int close(int fildes)
D closef PR I 0 ExtProc('close')
D handle I 0 value

16. P*--------------------------------------------------
P* Procedure name: writeXML
P* Purpose: Write out the lines to the file
P* Returns:
P* Parameter: fd => File Description to write to
P* Parameter: code => Key word that tells the procedure what to do
P* Parameter: tag => The xml tag to use
P* Parameter: data => The data to write out
P writeXML B EXPORT
D writeXML PI
D fd I 0 VALUE
D code A VALUE
D tag A VALUE
D data A VALUE
D attribute a value options(*nopass)

17. WHEN code = 'MIMIC' and %parms() = 4; mydata = %trim(data) + crlf;
SELECT;
WHEN code = 'MIMIC' and %parms() = 4;
mydata = %trim(data) + crlf;
callp write(fd: %addr(mydata): %len(%trim(mydata)));
WHEN code = 'MIMIC' and %parms() = 5;
mydata = %subst(Data : 1 : %len(%trim(Data)) - 1) + ' ' +
%trim(Attribute) + %subst(Data: %len(%trim(Data)) : 1) + crlf;
'</' + %trim(tag) + '>' + crlf;
callp write(fd:%addr(mydata):%len(%trim(mydata)));
ENDSL;

18. WHEN code = 'INFO' and %parms() = 4;
Data = XMLScrubStr(data:'N');
Data = XMLFixData(data:BadFound);
mydata = '<' + %trim(tag) + '>' + %trim(data) +
'</' + %trim(tag) + '>' + crlf;
callp write(fd:%addr(mydata):%len(%trim(mydata)));
WHEN code = 'INFO' and %parms() = 5;
mydata = '<' + %trim(tag) + ' ' + %trim(attribute) + '>' +
%trim(data) +
Endsl;

19. Error Handling If Retfield <> -1 Error = ErrNo();
ErrorFound = *ON;
Qp0zLprintf('--> Error Opening File: %s'+LF:%editc(Error:'X'));
Qp0zLprintf(' File Name: %s' + LF:%Trim(FullFileName));
Endif;

20. Other Functions Available
Checking Existance and Permissions
Retrieve Stream File Stats
Deleting Files
Renaming Files
Random File Positioning
Record position – create file where all records the same length
Reading / Writing / Updating record
Reading / creating / removing folders
Error Handling ErrNo_H

21. Other Resources