Opens a file for input or output.

Public Sub FileOpen( _
   ByVal FileNumber As Integer, _
   ByVal FileName As String, _
   ByVal Mode As OpenMode, _
   Optional ByVal Access As OpenAccess = OpenAccess.Default, _
   Optional ByVal Share As OpenShare = OpenShare.Default, _
   Optional ByVal RecordLength As Integer = -1 _
)

Parameters

FileNumber

Required. Any valid file number. Use the FreeFile function to obtain the next available file number.

FileName

Required. String expression that specifies a file name — may include directory or folder, and drive.

Mode

Required. Enum specifying the file mode: Append, Binary, Input, Output, or Random.

Access

Optional. Keyword specifying the operations permitted on the open file: Read, Write, or ReadWrite. Defaults to ReadWrite.

Share

Optional. Enum specifying the operations restricted on the open file by other processes: Shared, Lock Read, Lock Write, and Lock Read Write. Defaults to Shared.

RecordLength

Optional. Number less than or equal to 32,767 (bytes). For files opened for random access, this value is the record length. For sequential files, this value is the number of characters buffered.

Exceptions/Errors

Remarks

You must open a file before any I/O operation can be performed on it. FileOpen allocates a buffer for I/O to the file and determines the mode of access to use with the buffer.

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

The channel to open can be found using the FreeFile() function.

Example

This example illustrates various uses of the FileOpen function to enable input and output to a file.

The following code opens the file TESTFILE in Input mode.

FileOpen(1, "TESTFILE", OpenMode.Input)
' Close before reopening in another mode.
FileClose(1)

This example opens the file in Binary mode for writing operations only.

FileOpen(1, "TESTFILE", OpenMode.Binary,OpenAccess.Write)
' Close before reopening in another mode.
FileClose(1)

The following example opens the file in Random mode. The file contains records of the structure Person.

Structure Person
   <VBFixedString(30)> Dim Name As String
   Dim ID As Integer
End Structure
' Count 30 for the string, plus 4 for the integer.
FileOpen(1, "TESTFILE", OpenMode.Random, , , 34)
' Close before reopening in another mode.
FileClose(1)

This code example opens the file in Output mode; any process can read or write to file.

FileOpen(1, "TESTFILE", OpenMode.Output, OpenShare.Shared)
' Close before reopening in another mode.
FileClose(1)

This code example opens the file in Binary mode for reading; other processes can't read file.

FileOpen(1, "TESTFILE", OpenMode.Binary, OpenAccess.Read, _
   OpenShare.LockRead)

See Also

FileClose Function | FreeFile Function | File Access with Visual Basic Run-Time Functions | ArgumentException | IOException