After the above two statements execute, all subsequent commands that operate on the specific file can refer to it as fNum. The FreeFile() returns the next available file number, and unless this number is assigned to a file, FreeFile() returns the same number if called again. Each time you call FreeFile() to get a new file number, you must use it as the following example shows.

      fNum1 = FreeFile()
      Open "c:\mytestfile.txt" For Input As #fNum1
      fNum2 = FreeFile()
      Open "c:\yourtestfile.txt" For Input As #fNum2

The Open Statement 

      Dim numVal as Long, dateVal As Date
      Input #1, numVal, dateVal

You use the Line Input # statement to read from sequential files. The Line Input statement reads a single line of text from the file and assigns it to a string variable. It reads all the characters from the beginning of the file to the first new character. When you call it again, it returns the following characters, up to the next newline character. The new line characters are not part of the information stored to or read from the file, and they are used only as delimiters.

The file_number argument is the file's number, and strVar is the name of a variable where data read from the file will be stored. The following lines will read the first 2 text lines and assign them to the string variable textLine1 and textLine2.

      Line Input #fNum, textLine1
      Line Input #fNum, textLine2

The following lines write the same data as what the Print # statement will show you in the next example.

      Kill "C:\temp1.txt"
      Open "C:\temp1.txt" For Output As #1
      Write #1, "Poh Beng William", "Snr Planning Manager", 30
      Write #1, "Irene Zhang", "Planning Manager", 26
      Write #1, "Emily Seng", "Senior Planner", 25
      Write #1, "Josephine Kok", "Planner", 23

EOF() function accepts as an argument the number of an open file and returns True if the end of file has been reached. The LOF() function returns the length of the file, whose number is passed as an argument. The code below parses a text file, extract any lines containing the string called "PCBA", and add those lines to a listbox.

Private Sub CommandButton1_Click()
      Dim dText As String, sLine As String, Filename$
      Dim fNum As Integer

      Filename$ = "c:\vbautomation.110mb.dotcom\MyPartsList.txt"

      If Dir(Filename$) = "" Then Exit Sub
      fNum = FreeFile
       Open Filename$ For Input As #fNum

        While Not EOF(fNum)     ' returns True if it reaches end of file
        Line Input #fNum, sLine
        Debug.Print Seek(1), Left$(sLine, 5)       ' Seek statement sets the position for the next read/write operation.
             If (InStr(1, sLine, "PCBA") <> 0) Then
                    ListBox1.AddItem sLine
             End If
        Wend
        Close #fNum    ' this closes the file opened as fNum
End Sub

Opening and Reading a File

When you open a sequential file, you can't change its data. You can either read them, store them to another file, or overwrite the entire file with the new data. To do so, you must open the file for Input, read its data, then close the file. To overwrite the file, open it for Output, and save the data to it. When you open a file for Output, VisualBasic wipes out its entire contents, even if you don't write anything to it. if you don't want to overwrite an existing file but instead to append data to it, open it for Append.

The following statement opens a random-access file for reading from and writing to, using the record structure shown above:

Open "c:\CustomerList.txt" For Random As #1 Len=Len(Mrec)

Below example demonstrates opening and reading a text file, replaces the character ", one line at a time, and print the lines to range A1 in active sheet.

The Get statement is used read data from a file opened in binary mode. The syntax, as it applies to binary files is: 

varname = Input(number, [#] filenumber) 

where varname is the string variable into which the file data will be stored, number is the number of characters to be read, and filenumber is a valid filenumber identifying the file from which you want to read. 

The following table contains examples that contrast the Get statement and Input function as ways of reading data from a binary file: 

The filenumber is any valid filenumber as defined above. 

Byte position is the byte position within the file at which the writing begins. The byte position is "one-based", meaning the first byte position in the file is 1, the second position is 2, and so on. You can omit this entry, in which case the next byte following the last Get or Put statement is written. If you omit the byte position entry, you must still include the delimiting commas in the Put statement, for example: 

Put #intMyFile, , strData 

Varname is a string variable from which the data will be written. This string variable is often referred to as a "buffer" when processing binary files. It is important to note that the length, or size, of this string variable determines how many bytes of data will be written to the file. 

For example, the following statements cause 1 byte of data to file number "intMyFile": 

strCharacter = Mid$(strData, lngCurrentPos, 1)

Put #intMyFile, , strCharacter 

Recall that you can omit the "byte position" entry, in which case VB will "keep track" of where it is in the file. For example, the first time the above Put statement is executed, byte 1 will be written; the second time the above Put statement is executed, byte 2 will be written; and so on.