Using Stream and Record I/O Functions with iSeries Data
Management Files

This chapter describes how to open, write, read, and update:

• Text stream files
• Binary stream files

The American National Standards Institute (ANSI) defines a C language stream file as a sequence of data that is read and written one character at a time. All I/O operations in ANSI C are stream operations.

On the iSeries Data Management system, all files are made up of records. All I/O operations at the operating system level are carried out a record at a time, using data management operations.

The ILE C/C++ run-time library allows your program to process stream files as text stream files or as binary stream files. Text stream files process one character at a time. Binary stream files process one character at a time or one record at a time. Since the iSeries Data Management system carries out I/O operations one record at a time, the ILE C/C++ library simulates stream file processing with OS/400 records. Although the ILE C/C++ library logically handles I/O one character at a time, the actual I/O that is performed by the operating system is done one record at a time.

Note: Since the iSeries Data Management system carries out I/O operations one record at a time, using system commands such as OPNQRYF together with stream I/O operations on the same file may cause positioning problems in the file your program is processing.Do not mix the use of ILE C/C++ extensions for record I/O and stream file functions on the same file as unpredictable results can occur. Avoid using system commands that logically work with records instead of characters in programs that contain stream I/O operations.