VB.NET Language in a Nutshell, Second Edition

Name

InputString Function

Class

Microsoft.VisualBasic.FileSystem

Syntax

InputString(filenumber, charcount)

filenumber (required; Integer)

Any valid file number

charcount (required; Integer)

Number of characters to read from file

Return Value

A String containing charcount characters

Description

Reads data from a file into a string variable

Rules at a Glance

• InputString should only be used with files opened in input (OpenMode.Input) or binary mode ( OpenMode.Binary).

• InputString begins reading from the current position of the file pointer.

• InputString returns all the characters it reads, regardless of their type. This include spaces, carriage returns, linefeeds, commas, end-of-file markers, unprintable characters, etc.

• Once the function finishes reading charcount characters, it also advances the file pointer charcount characters.

Example

If the file c:\data.txt contains the data:

abcdefghijklmnopq

the following code reads the characters, three at a time:

Dim fr As Integer = FreeFile(  )
Dim sLine As String
Dim i As Long
FileOpen(fr, "c:\data2.txt", OpenMode.Input)

For i = 1 To LOF(fr) \ 3
   sLine = InputString(fr, 3)
   Console.WriteLine(sLine)
Next

FileClose(fr)

Programming Tips and Gotchas

• InputString reads data written to a file using the Print, PrintLine, or FilePut functions.

• InputString always attempts to precisely read charcount characters from the file. If there are no charcount characters from the position of the file pointer to the end of the file, InputString attempts to read beyond the ...