At a glance

A file descriptor is an abstract value, that contains all the necessary information for the handle of a file:

• A pointer to the file,

• the access rights to this file,

• the access conditions to the file (read, write or read/write),

• the current position in the file, etc.

Operation

It is possible to use one or more descriptors simultaneously or sequentially on one file in order to create multiple accesses (read, write or read/write) at the same position or at different positions (beginning, end, middle etc...).

A file descriptor is:

• Allocated (via OPEN_FILE, CREATE_FILE),

• used (via RD_FILE_TO_DATA, WR_DATA_TO_FILE, SEEK_FILE, GET_FILE_INFO),

• realesed (via CLOSE_FILE).

It is used to identify a transaction to a file and it is possible to have many transactions on the same file.

EFB instance

The EFB instance is considered as a tool that realize an action on a file in a given context. The instance is represented by the file descriptor.

With the same EFB instance, it is possible to work on many transactions sequentially through one or many file descriptors.

Via these file descriptors, it is posssible to work on the same file or on different files.