Again, what file system is your ‘flat file’ in?

If it is a program-described ‘flat file’ in the /QSYS.LIB file system, or just a file with a single field in the record format, you can potentially get it done with some messy programming.

However, you would probably do best by doing all of the work in temporary database files. Once you have the records in database files the way you want them, you can simply convert them to .CSV format. The conversion could be as easy as a single CPYTOIMPF command.

It would be far easier doing it that way.

Tom

On AS/400s, that usually means that the file resides in the /root file system (or a similar file system).

If that isn’t what you intend, then please give a more complete description of the file. Especially, what file system does it reside in?

Tom

Generally, you don’t. That’s not how updating usually works for streamfiles.

There are two general methods.

1. Open the file for reading. Open a second temporary file for writing. Read the data from the first file and copy to the second file. When you reach a point where you want to insert or delete or modify, then output the data to the second file as you want the change to be. Continue reading from one and writing to the other until you process the entire input file. Close the two files. Delete or rename the first file. Rename the second file to the original name and set its appropriate ownership and authority.
2. Or read the entire file into memory. Make the updates in memory. When finished, copy your memory back out to the file.

Some of that helps to explain why many database files will have more fixed-length records and fields. The database management layer handles the parts about repositioning within the file, and it is far easier when each record has the same length. This type of data processing is far better suited for database files.

You can read and reposition in the file. See for example the lseek()–Set File Read/Write Offset API, but it’s almost certain you don’t want to use it for what you’re asking about.

Tom