Accessing Files Programmer's Guide (32650-90885)
Chapter 2 19
Creating A File
The HPFOPEN Intrinsic
Aborting NOWAIT I/O
Occasionally, after a process has started a NOWAIT I/O with FREAD or FWRITE, something
occurs that causes completion of that I/O to be no longer needed. Perhaps the process is
"shutting down" and does not want to wait for the I/O (that is, to issue IOWAIT or
IODONTWAIT).
MPE/iX lets the process abort NOWAIT I/Os that have not yet completed by using
FCONTROL with a control code of 43. A condition code of CCE is returned if the I/O was
aborted; in this case, nothing more needs to be done. CCG is returned if the I/O has already
completed; in this case, IODONTWAIT or IOWAIT must be called to clear it. CCL and FSERR
79, No NOWAIT I/O pending for special file are returned if there was nothing to
abort.
Limitations
Currently, MPE/iX does not support NOWAIT I/O to message files across a network. In
most cases, this is not an important limitation, because it is rare that both readers and
writers to the same message file need to use NOWAIT I/O. If the file is made local to the
accessor that needs NOWAIT I/O, the other accessor can then do WAIT I/O across the
network.
More information on these intrinsics is found in the MPE/iX Intrinsics Reference Manual.
For detailed information about WAIT and NOWAIT, consult the Interprocess
Communications Programmers' Guide.
The following lists the optional parameters you can use to specify a file's physical
characteristics, as well as the default values for each.
Itemnum/
Mnemonic Item Description
0 End of option list:
There is no corresponding
item
. The absence of an
itemnum
after the last
itemnum
,
item
pair is equivalent to specifying this option.
2/CA Formal designator:
Passes a formal file designator that is interpreted according to
MPE-escaped semantics (unless another syntax has been chosen via item
41). The first charater is interpreted as a delimiter, and all subsequent
characters, up to the next occurrence of the delimiter, comprise the formal
designator. The file name must be terminated by a nonalphanumeric
character other than a period (.), a slash (/), a hyphen (-), and an
underscore (_). Use of matched starting and ending name delimiters (a
quoted name) alleviates the need for a terminating character other than
the quote characters.
The file referred to by
formaldesig
can be either an MPE file (i.e., one
that uses MPE syntax) or it can follow HFS syntax. If
formaldesig
follows
MPE syntax, the file name can include password, group, and account
specifications. The file name can backreference a file equation and
optionally be preceded by an asterisk. If
formaldesig
follows HFS syntax,