Random Files Generator

Whilst doing some house keeping on some old VBScript files the other day I came across one for creating test files. I’ve blogged previously about creating test files using my MTF utility and whilst it or fsutil can be very useful, this script filled a particular niche. It was created as part of a test suite of scripts it creates multiple files of a specific size filled with random printable content.

The script below shows an example of how to use the GenerateFiles function, which is the heart of the script. The function takes a set of five parameters.

  1. The number of files to be produced.
  2. The directory in which the files are to be written (including trailing slash).
  3. The file extension for the files to be written (no “.” required).
  4. The number of characters to be written to the file (1 character -> 1 byte).
  5. The fast processing flag (TRUE/FALSE).

Hopefully most of the parameters are self explanatory, but the last one is worth a bit more explanation.

When fast processing is enabled, the same basic content will be used for each file that is produced. It will be identical in each file save for the first few characters which will give the name of the file (without the file extension) followed by a space. When fast processing is disabled, the content in each file will be randomly generated independently for each file.

The file names used for the files are numeric starting at zero. The script knows how many files to produce and so prefixes each file name with the requisite number of zeros so that they order numerically in the file system when sorting by name.

e.g. if 100 files with a file extension of “txt” were being created, the file names would be 00.txt, 01,txt, …, 98.txt and 99.txt.

As a final note, the RANDOM_CHARACTERS string (see FileContent function) is used to generate the content for the files so if there are any specific character sets you want to use (e.g. just numbers, no upper case characters, no symbols) you can tailor it to suit your own needs.

Option Explicit

Const OUTPUT_FOLDER = "C:\Users\sylumer\Scripts\vbs\ManyTestFiles\Output\"
Const NO_OF_FILES = 5
'One character will stored as one byte of information
Const FILE_EXTENSION = "txt"
'Const FAST = True
Const FAST = False


Function GenerateFiles(p_intNoOfFiles, p_strOuputDirectory, p_strFileExtension, p_intCharactersInEachFile, p_strFastProcessing)
    Dim objFSO, intCounter, fhOutputFile, strFileName, strFileContent, strFileStaticContent

    Set objFSO = CreateObject("Scripting.FileSystemObject")
    'If speed is require rather than total randomness, we'll save some text to add on after the file ID
    If p_strFastProcessing then
        strFileStaticContent = FileContent(p_intCharactersInEachFile - Len(p_intNoOfFiles - 1) - 1)
    End if

    'Create the files using a numeric ID (starting at zero)
    For intCounter = 0 to (p_intNoOfFiles - 1)
        'Generate the next file name
        strFileName = p_strOuputDirectory & ExpandNumber(intCounter, p_intNoOfFiles - 1) & "." & p_strFileExtension
        'Write the appropriate quantity of content to file
        Set fhOutputFile = objFSO.CreateTextFile(strFileName, true)
        If p_strFastProcessing then
            'Using the same random content in each file (with a prefix relating to the file ID
            strFileContent = ExpandNumber(intCounter, p_intNoOfFiles - 1) & " " & strFileStaticContent
            'Generating unique random content for each file 
            strFileContent = FileContent(p_intCharactersInEachFile)
        End If

    'Notify user of completion
    MsgBox p_intNoOfFiles & " files generated in" & vbCrLf & """" & OUTPUT_FOLDER & """", vbInformation, "Generation Complete"
End Function

'Pad a number to a specified number of characters by prefixing with zeros.
Function ExpandNumber(p_strNum, p_strBase)
    ExpandNumber = p_strNum
    While Len(ExpandNumber) < Len(p_strBase)
        ExpandNumber = "0" & ExpandNumber
End Function

'Generate a string of random printable characters to a specified length.
Function FileContent(p_intLength)
    Const RANDOM_CHARACTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMONPQRSTUVWXYZ1234567890!!?$%^&*()_+-={}[];'#:@~,./<>?\|`?

    Dim intCounter
    For intCounter = 1 To p_intLength
        FileContent = FileContent & Mid(RANDOM_CHARACTERS, Int(Rnd() * Len(RANDOM_CHARACTERS) + 1), 1)
End Function
Author: Stephen Millard
Tags: | scripting | vbs |

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