The predefined procedure associate associates
a logical file with an open physical file, and puts the current
position index at the first component.
Syntax
associate (logical_file, file_number, open_options) |
Parameters
Title not available (Associate Procedure )
- logical_file
The name of the logical file.
- file_number
The file number of the open physical file. The physical
file must have been opened with a direct call to an operating system
routine or a non-Pascal routine. You cannot call the associate
procedure with the file number of a closed file or a file that was
opened with the Pascal procedure append,
associate, open,
reset, or rewrite.
- open_options
One of the following options. It must be a string
literal:
Title not available (Associate Procedure )
- 'READ'
Associate with sequential access file with read-only
access.
- 'WRITE'
Associate with sequential access file with write-only
access.
- 'READ,DIRECT'
Associate with direct access file with read-only
access.
- 'WRITE,DIRECT'
Associate with direct access file with write-only
access.
- 'READ,WRITE,DIRECT'
Associate with direct access file with read-write
access.
- 'DIRECT'
Associate with direct access file with read-write
access (same as 'READ, WRITE, DIRECT' ).
- 'NOREWIND'
Associates with a file without changing the current
file position.
You must specify one of the above strings for open_options.
The system-dependent open options listed in Appendix A “MPE/iX Dependencies ” (for MPE/iX) and Appendix B “HP-UX Dependencies ” (for HP-UX) apply to the file-opening procedures
append, open,
reset, and rewrite.
Pascal ignores them when they are used with associate.
You cannot specify read access if the physical file is not
open for read access, or to specify write access if it is not open
for write access. If you associate a logical file with an empty
physical file, for read access, the next read causes an error.
Table 3-3 “Characteristics of Associate Procedure” summarizes the
characteristics of the predefined procedure associate.
Table 3-3 Characteristics of Associate Procedure
Type of File That it Can Open | Any. |
State in Which it Opens File | Specified in open_options. |
Manner in Which File Can Be Accessed | Either — Defined by characteristics
of physical file. |
Purpose for Which it Opens File | Input, output or both. |
Where it Puts Current Position Index | Before first component. |
Value of eof
for File * | False unless opened for write, in which
case eof returns true despite possible
old data after the current component. |
Erases Old file Contents | No. |
File Buffer Variables * | First component for a textfile that is
open for reading; undefined otherwise. |
Title not available (Associate Procedure )
For a nonempty file. For an empty file, every file-opening
procedure puts the current position index before the [nonexistent]
first component, eof returns true,
and the file buffer variable is undefined.
If the physical file is not empty, the first reference to
its file buffer variable loads its file buffer with its first component.
If the physical file is empty, the first reference to its file buffer
variable causes an error.
Figure 3-5 “Effect of Associate Procedure
on Open File” illustrates the
effect of the associate procedure on the open
file whose file number is file_num:
Condition of file:
After associate(examp_file,file_num,'READ'),
the file is open in the read-only state and looks like this:
Now examp_file is open in the read-only
state.
Example 1
This example applies to HP Pascal on the MPE/iX operating
system only. For a description of the MPE/iX intrinsic FOPEN, refer
to the MPE/iX Intrinsics Reference Manual.
List 1 Here.
Example 2
This example applies to HP Pascal on the HP-UX operating system
only. For descriptions of the HP-UX routines tmpnam
and open, refer
to the HP-UX Reference manual.
List 2 Here.
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