FileSystem.Seek Method

Definition

Namespace:

Microsoft.VisualBasic

Assembly:

Microsoft.VisualBasic.Core.dll

Returns a Long specifying the current read/write position in a file opened by using the FileOpen function, or sets the position for the next read/write operation in a file opened by using the FileOpen function. The My feature gives you better productivity and performance in file I/O operations than Seek. For more information, see FileSystem.

Overloads

Seek(Int32)	Returns a Long specifying the current read/write position in a file opened by using the FileOpen function, or sets the position for the next read/write operation in a file opened by using the FileOpen function. The My feature gives you better productivity and performance in file I/O operations than Seek. For more information, see FileSystem.
Seek(Int32, Int64)	Returns a Long specifying the current read/write position in a file opened by using the FileOpen function, or sets the position for the next read/write operation in a file opened by using the FileOpen function. The My feature gives you better productivity and performance in file I/O operations than Seek. For more information, see FileSystem.

Seek(Int32)

Source:

FileSystem.vb

Returns a Long specifying the current read/write position in a file opened by using the FileOpen function, or sets the position for the next read/write operation in a file opened by using the FileOpen function. The My feature gives you better productivity and performance in file I/O operations than Seek. For more information, see FileSystem.

public:
 static long Seek(int FileNumber);

public static long Seek (int FileNumber);

static member Seek : int -> int64

Public Function Seek (FileNumber As Integer) As Long

Parameters

FileNumber

Int32

Required. An Integer that contains a valid file number.

Returns

Int64

A Long specifying the current read/write position in a file opened by using the FileOpen function, or sets the position for the next read/write operation in a file opened by using the FileOpen function.

Exceptions

IOException

File mode is invalid.

Examples

This example uses the Seek function to return the current file position. The example assumes TestFile is a file that contains records of the structure Record.

Structure Record   ' Define user-defined type.
    Dim ID As Integer
    Dim Name As String
End Structure

For files opened in Random mode, Seek returns the number of next record.

FileOpen(1, "TESTFILE", OpenMode.Random)
Do While Not EOF(1)
    WriteLine(1, Seek(1))   ' Write record number.
    FileGet(1, MyRecord, -1)   ' Read next record.
Loop
FileClose(1)

For files opened in modes other than Random mode, Seek returns the byte position at which the next operation occurs. Assume TestFile is a file that contains several lines of text.

' Report character position at beginning of each line.
Dim TextLine As String
FileOpen(1, "TESTFILE", OpenMode.Input)   ' Open file for reading.
While Not EOF(1)
    ' Read next line.
    TextLine = LineInput(1)
    ' Position of next line.
    MsgBox(Seek(1))
End While
FileClose(1)

This example uses the Seek function to set the position for the next read or write in a file.

For files opened in modes other than Random mode, Seek sets the byte position at which the next operation occurs. Assume TestFile is a file that contains several lines of text.

Dim someText As String = "This is a test string."
' Open file for output.
FileOpen(1, "TESTFILE", OpenMode.Input)
' Move to the third character.
Seek(1, 3)
Input(1, someText)
Console.WriteLine(someText)
FileClose(1)

Remarks

Seek returns a value between 1 and 2,147,483,647 (equivalent to 2^31 - 1), inclusive.

The following describes the return values for each file access mode:

Mode	Return Value
Random	Number of the next record read or written
Binary, Input, Output, Append	Byte position at which the next operation occurs. The first byte in a file is at position 1, the second byte is at position 2, and so on.

See also

• FileGet
• Loc(Int32)
• FileOpen(Int32, String, OpenMode, OpenAccess, OpenShare, Int32)
• FilePut
• IOException
• Reading from Files in Visual Basic
• Writing to Files in Visual Basic

Seek(Int32, Int64)

Source:

FileSystem.vb

Returns a Long specifying the current read/write position in a file opened by using the FileOpen function, or sets the position for the next read/write operation in a file opened by using the FileOpen function. The My feature gives you better productivity and performance in file I/O operations than Seek. For more information, see FileSystem.

public:
 static void Seek(int FileNumber, long Position);

public static void Seek (int FileNumber, long Position);

static member Seek : int * int64 -> unit

Public Sub Seek (FileNumber As Integer, Position As Long)

Parameters

FileNumber

Int32

Required. An Integer that contains a valid file number.

Position

Int64

Required. Number in the range 1-2,147,483,647, inclusive, that indicates where the next read/write operation should occur.

Exceptions

IOException

File mode is invalid.

Examples

This example uses the Seek function to return the current file position. The example assumes TestFile is a file that contains records of the structure Record.

Structure Record   ' Define user-defined type.
    Dim ID As Integer
    Dim Name As String
End Structure

For files opened in Random mode, Seek returns the number of next record.

FileOpen(1, "TESTFILE", OpenMode.Random)
Do While Not EOF(1)
    WriteLine(1, Seek(1))   ' Write record number.
    FileGet(1, MyRecord, -1)   ' Read next record.
Loop
FileClose(1)

For files opened in modes other than Random mode, Seek returns the byte position at which the next operation occurs. Assume TestFile is a file that contains several lines of text.

' Report character position at beginning of each line.
Dim TextLine As String
FileOpen(1, "TESTFILE", OpenMode.Input)   ' Open file for reading.
While Not EOF(1)
    ' Read next line.
    TextLine = LineInput(1)
    ' Position of next line.
    MsgBox(Seek(1))
End While
FileClose(1)

This example uses the Seek function to set the position for the next read or write in a file.

For files opened in modes other than Random mode, Seek sets the byte position at which the next operation occurs. Assume TestFile is a file that contains several lines of text.

Dim someText As String = "This is a test string."
' Open file for output.
FileOpen(1, "TESTFILE", OpenMode.Input)
' Move to the third character.
Seek(1, 3)
Input(1, someText)
Console.WriteLine(someText)
FileClose(1)

Remarks

Seek returns a value between 1 and 2,147,483,647 (equivalent to 2^31 - 1), inclusive.

The following describes the return values for each file access mode:

Mode	Return Value
Random	Number of the next record read or written
Binary, Input, Output, Append	Byte position at which the next operation occurs. The first byte in a file is at position 1, the second byte is at position 2, and so on.

See also

• FileGet
• Loc(Int32)
• FileOpen(Int32, String, OpenMode, OpenAccess, OpenShare, Int32)
• FilePut
• IOException
• Reading from Files in Visual Basic
• Writing to Files in Visual Basic