| UPDATE ... .
1. ... INPUT
2. ... OUTPUT
3. ... APPENDING
4. ... UPDATE
These additions are used to open the file for reading, writing, appending, or changing. In
Unicode programs, specification of the access type is obligatory.
The addition FOR INPUT opens the file for reading. By default, the file pointer is set at the start of the file. If the file specified does not exist, sy-subrc is set to 8.
In a Unicode program, it is not possible to obtain write access to a file that is open for reading. In a
non-Unicode program write access is also permitted.
The addition FOR OUPUT opens the file for writing. If
the specified file already exists, its content is deleted. If the file specified does not exist, it is created. Read access is also permitted.
The addition FOR APPENDING opens the file for appending.
If the file specified already exists, it is opened and the file pointer is set at the end of the file.
If the file specified does not exist, it is created. Attempted read access to a file opened with
FOR APPENDING with the statement
READ DATASET fails, and returns the value 4 for sy-subrc.
The addition FOR UPDATE opens the file for changes to
the existing content. By default, the file pointer is set to the start of the file. If the specified file does not exist, no file is opened and sy-subrc is set to 8.