FOPEN_ program instruction FOPEN_ program instruction Syntax FOPEN_ (lun, record_len, mode ) file_spec Function Open a disk file for read-only, read-write, read-write-append, or read-directory, as indicated by the last letter of the instruction name. The forms of FOPEN_ are: l FOPENA l FOPEND l FOPENR l FOPENW See the Details section for descriptions of each instruction. Usage Considerations A logical unit must be attached before an open operation will succeed. No more than 60 disk files and 160 network files can be open by the entire system at any time. That includes files opened by all of the program tasks and by the system monitor (for example, for an FCOPY command).
Parameters lun Real-valued expression defining the logical unit number of the disk device to be accessed. (See the ATTACH instruction for a description of unit numbers.) record_len Optional real-valued expression defining the length of records to be read and written. If the record length is omitted or is zero, variable-length records are processed. In this case, random access of records cannot be done. If the record length is nonzero, it specifies the length (in characters) of fixed-length records to be processed. Random access is allowed with fixed-length records. mode Optional real-valued expression defining how read access is to be done.
The value specified is interpreted as a sequence of bit flags as eV+Language Reference Guide, v2.x, 18319-000 Rev A Page 247