Open statement

Open filename$ [For mode] [Access access] As [#]filenumber

Opens a file for input and output operations.

You must open a file before any I/O operation can be performed on it. The Open statement has the following parameters:

filename

File name or path.

mode

Reserved word that specifies the file mode: Append, Binary, Input, Output.

access

Reserved word that specifies which operations are permitted on the open file: Read, Write.

filenumber

Integer expression with a value between 1 and 255, inclusive. When an Open statement is executed, filenumber is associated with the file as long as it is open. Other I/O statements can use the number to refer to the file.

If file doesn't exist, it is created when a file is opened for Append, Binary or Output modes.

The argument mode is a reserved word that specifies one of the following file modes.

Mode	Description
Input	Sequential input mode.
Output	Sequential output mode.

Append Sequential output mode. Append sets the file pointer to the end of the file. A Print # or Write # statement then extends (appends to) the file.

The argument access is a reserved word that specifies the operations that can be performed on the opened file. If the file is already opened by another process and the specified type of access is not allowed, the Open operation fails and a Permission denied error occurs. The Access clause works only if you are using a version of MS-DOS that supports networking (MS-DOS version 3.1 or later). If you use the Access clause with a version of MS-DOS that doesn't support networking, a feature unavailable error occurs. The argument access can be one of the following reserved words.

Access type	Description
Read	Opens the file for reading only.
Write	Opens the file for writing only.
Read Write	Opens the file for both reading and writing. This mode is valid only for Random and Binary files and files opened for Append mode.

Example

The following example writes data to a test file and reads it back.

Sub Main()
   Open "TESTFILE" For Output As #1   ' Open to write file.
   userData1$ = InputBox("Enter your own text here")
   userData2$ = InputBox("Enter more of your own text here")
   Write #1, "This is a test of the Write # statement."
   Write #1,userData1$, userData2
   Close #1
 
   Open "TESTFILE" for Input As #2   ' Open to read file.
   Do While Not EOF(2)
       Line Input #2, FileData   ' Read a line of data.
       PRint FileData   ' Construct message.
 
   Loop
   Close #2   ' Close all open files.
   MsgBox "Testing Print Statement"   ' Display message.
   Kill "TESTFILE"   ' Remove file from disk.
End Sub