MPE/iX Intrinsics Reference Manual (32650-90905)

140 Chapter5
Command Definitions (FCONTROL - FLOCK)
FCONTROL
writer's ID. Each record read has a two-word header. The first word
indicates the type of record:
0 Data record
1 Open record
2 Close record
The second word contains the writer's ID number. If the record is a data
record, the data follows the header. Open and close records contain no
more information. If the
item value is 0, reading the writer's ID is
disabled. Only data is read to the reader's target area. The open and close
records are skipped and deleted by the file system when they come to the
head of the message queue, and the two-word header is transparent to the
reader.
Default: 0
47/U16 Nondestructive read:
Applicable only if
filenum specifies a message file.
If the
item value is 1, the next FREAD by this reader does not delete the
record. Subsequent FREAD calls are unaffected. When
item is specified as
0, the next FREAD deletes the record.
Default: 0
48/U16 Arm/disarm software interrupts:
Passes a value that arms/disarms the software interrupt mechanism (valid
only if
filenum specifies a message file). To arm the file's software
interrupt, pass the external procedure label (NM plabel) or the interrupt
procedure. To disarm the software interrupt, pass a value of zero.
51 Append mode:
Enables or disables append mode based on the value of the
item
parameter. Append mode is enabled if item is one (1) and disabled if item
is zero (0). Write operations append data at the end of a file while reads
and seeks may occur anywhere within the file when POSIX append mode
is enabled for that file.
Append
mode differs from opening a file for append access in several
ways:
1 Append
mode can be enabled and disabled while a file is
open. Append
access is established when opening a file
and cannot be changed dynamically for a file number.
2 Append
access is a process-local attribute affecting only
the access of the process which opened the file. Append
mode affects all processes sharing a logical record pointer.
(The MULTI and GMULTI options permits logical record
pointers to be shared.)
3 A file's logical record pointer can be manipulated through