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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Create user-defined routines
Write a user-defined routineThis section outlines some implementation issues for C user-defined routines (UDRs). This section also describes the specific features and tasks of a C UDR.
Perform input and outputBecause a C UDR executes in the context of the database server, it must not use the standard input/output (I/O) calls such as scanf() and printf(). The DataBlade® API provides support for I/O on a generic stream and I/O on an operating-system file from a UDR.
Access to operating-system filesThe DataBlade® API provides file-access functions for access to operating-system files from within a C UDR. These functions provide file management that is similar to what operating-system file-access functions provide.
Open a fileThe mi_file_open() function is the constructor function for a file descriptor. Through the file descriptor, you access an operating-system file.
Call the operating-system open callTo open a file, the mi_file_open() function calls the open system call that your operating system supports.
Specify the open modeThe mi_file_open() function takes as its third argument the open mode in which to open the operating-system file. The open mode specifies the ownership of the file.

Specify the open mode

The mi_file_open() function takes as its third argument the open mode in which to open the operating-system file. The open mode specifies the ownership of the file.

The mi_file_open() function passes this open mode directly to the underlying operating-system call. The semantics for mode must match those that the underlying operating-system call supports.

For example, the mi_file_open() call in Sample call to open an operating-system file specifies an open mode of 0644:

Read/write for owner
Read-only for group
Read-only for general public

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