Open System Services System Calls Reference Manual (G06.29+, H06.08+, J06.03+)

System Functions (n - p) PUT_WRITEX(2)
If the PUT_WRITEX() call is to an unstructured disk file, data
is transferred to the record location specified by the next-record
pointer. The next-record pointer is updated to point to the record
following the record written.
Number of bytes written
If an unstructured file is created with the odd unstructured attri-
bute (also known as ODDUNSTR) set, the number of bytes writ-
ten is exactly the number specified in write_count. If the odd
unstructured attribute is not set when the file is created, the
value of write_count is rounded up to an even value before the
PUT_WRITEX() is executed.
You set the odd unstructured attribute with the Guardian
FILE_CREATE_, FILE_CREATELIST_, or CREATE pro-
cedure, or with the File Utility Program (FUP) SET and
CREATE commands.
File pointers after an PUT_WRITEX() call
After a successful PUT_WRITEX() call to an unstructured file,
the file pointers have these values:
• Current-record pointer is the next-record pointer.
• Next-record pointer is the next-record pointer plus the
count written.
• End-of-file (EOF) pointer is the maximum of the EOF
pointer or the next-record pointer.
Use on files opened for nowait I/O
• If the buffer is in an extended data segment, you cannot
deallocate or reduce the size of the extended data seg-
ment before the I/O completes with a call to the Guar-
dian AWAITIOX procedure or is canceled by a call to
the PUT_CANCEL( ) function or the Guardian CAN-
CELREQ procedure.
• You must not modify the buffer before the I/O completes
with a call to the Guardian AWAITIOX procedure. This
restriction also applies to other processes that might be
sharing the segment. It is the application’s responsibil-
ity to ensure this.
• If you initiated the I/O with PUT_WRITE(), the I/O
must be completed with a call to the Guardian
AWAITIOX procedure.
• A selectable extended data segment containing the
buffer need not be in use at the time of the call to
AWAITIOX.
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