|
open
+-(BOTH-| Write Options |--+ +-SHARED-----+
>>-open--+--------------------------+--+------------+----------->
+-(READ--------------------+ +-SHAREREAD--+
+-(WRITE-| Write Options |-+ +-SHAREWRITE-+
+-----------------------------------+
V |
>----+-------------------------------+-+--+---+----------------><
+-NOBUFFER----------------------+ +-)-+
+-BINARY--+-------------------+-+
+-RECLENGTH--length-+
[Write Options:]
+-------------+
V +-APPEND--+ |
|----+---------+-+----------------------------------------------|
+-REPLACE-+
Opens the stream and returns
READY:. If the method is unsuccessful, it
returns an error message string in the same form that the
[description] method uses.
For most error conditions, the additional information is in the form of
a numeric return code. This return code is the value of
ERRNO,
which is set whenever one of the file system primitives returns with a
-1.
By default, [open]
opens the stream for both reading and writing data, for
example: 'open BOTH'. To specify that the
stream be only opened for input or output,
specify READ or WRITE.
The options for the
[open] method are:
| READ |
Opens the stream for input only.
|
| WRITE |
Opens the stream for output only.
|
| BOTH |
Opens the stream for both input and output. (This is the
default.) The stream maintains separate read and write pointers.
|
| APPEND |
Positions the write pointer at the end of the stream.
(This is the default.)
The write pointer cannot be moved anywhere within the extent of the file as
it existed when the file was opened.
|
| REPLACE |
Sets the write pointer to the beginning of the stream
and truncates
the file. In other words, this option deletes all data that was in the stream
when opened.
|
| SHARED |
Enables another process to work with the stream in a shared mode. (This
is the default.) This mode must be compatible with the shared mode (SHARED,
SHAREREAD, or SHAREWRITE) used by the process that opened the stream.
|
| SHAREREAD |
Enables another process to read the stream in a shared mode.
|
| SHAREWRITE |
Enables another process to write the stream in a shared mode.
|
| NOBUFFER |
Turns off buffering of the stream. All data written to the stream is
flushed immediately to the operating system for writing. This option can have
a severe impact on output performance. Use it only when data integrity is
a concern, or to force interleaved output to a stream to appear in the exact
order in which it was written.
|
| BINARY |
Opens the stream in binary mode. This means that line-end
characters are ignored; they are treated like any other byte of data. This is
for processing binary record data using the line
operations.
Note
Specifying the BINARY option for a stream that
does not exist but is opened for writing also requires the RECLENGTH option
to be specified. Omitting the RECLENGTH option in this case raises an error
condition.
|
| RECLENGTH
[length]
|
Allows the specification of an exact length for each line
in a stream.
This allows line operations on binary-mode streams to operate on individual
fixed-length records. Without this option, line operations on binary-mode
files operate on the entire file (for example, as if you specified the
RECLENGTH option with a length equal to that
of the file). The
[length]
must be
1 or greater.
|
Stream object - OPEN method
stream_name~open
stream_name~open("write")
stream_name~open("read")
|