FileSystem module

The FileSystem module groups together the procedures and statements for working with files and directories on disk. Its members divide cleanly into two camps: pathname-based operations that act on something named in the filesystem (creating and deleting files and directories, querying their attributes, iterating over a directory listing), and file-number-based operations that act on a handle previously returned by the Open statement (reading, positioning, formatting, and tracking the channel).

ChDrive changes the current drive, ChDir changes the current directory on a given drive, and CurDir returns the path of the current drive — or of any other drive, if one is named. MkDir and RmDir create and remove directories.

ChDrive "D"
ChDir "D:\Projects"
Debug.Print CurDir              ' "D:\Projects"
MkDir "D:\Projects\Output"

Inspecting files and directories

Dir is the wildcard matcher: pass it a pathname containing * or ? and it returns the first matching name, then call it again with no arguments to step through subsequent matches until it returns "". FileLen returns the size of a file in bytes without opening it, and FileDateTime returns its last-modified timestamp. GetAttr and SetAttr read and write the VbFileAttribute flag bits — read-only, hidden, system, archive — and GetAttr also reports whether a name refers to a directory by setting the vbDirectory bit.

Dim Name As String
Name = Dir("C:\Logs\*.log")
Do While Name <> ""
    Debug.Print Name & vbTab & FileLen("C:\Logs\" & Name)
    Name = Dir
Loop

Copying and deleting

FileCopy copies one file to another, and Kill deletes files matching a wildcard pattern. Both operate by pathname and raise a run-time error when asked to act on a file the current process has open.

FileCopy "C:\Data\report.xlsx", "C:\Backup\report.xlsx"
Kill "C:\Backup\*.tmp"

Opening and tracking file numbers

The lower-level read/write statements — Open, Close, Get, Put, Print, Write, Input, and Line Input — work in terms of a file number in the range 1–511. FreeFile returns the next number that isn’t currently in use, sparing the caller from picking one by hand and racing other code to it. Once a file is open, FileAttr reports the access mode — Input, Output, Random, Append, or Binary — that the file number was opened with. Reset closes every file number currently open and flushes its buffers, and is most useful as a last-ditch cleanup before exit.

Dim N As Long
N = FreeFile
Open "C:\Data\report.txt" For Input As #N
' ... read ...
Close #N

Position within an open file

For an open file number, EOF returns True once a sequential read has run past the last record, LOF returns the file’s total length in bytes, and Loc returns the current read/write position. The unit of position depends on the open mode — record number for Random, byte offset for Binary, and the byte position divided by 128 for sequential modes — so the per-mode tables on each function’s page are the authoritative reference. Seek doubles as a function and a statement: the function returns the position of the next read or write (whereas Loc reports the position of the last), and the statement repositions the file pointer ahead of the next operation.

Dim N As Long, Line As String
N = FreeFile
Open "C:\Data\big.log" For Input As #N
Do While Not EOF(N)
    Line Input #N, Line
Loop
Close #N

Reading and formatting through open file numbers

Input and Input$ return a fixed number of characters read from a file number opened with Open, as a Variant or a String respectively; InputB and InputB$ are their byte-oriented counterparts, counting raw bytes rather than UTF-16 characters. They differ from the Input # statement in that they return every character they read — commas, newlines, quotation marks, leading spaces, and all — making them the right choice when the bytes on disk are not a stream of comma-delimited values.

Width sets the output line width on a sequential output channel: subsequent Print # wraps to a new line once the chosen number of characters has been written, or never wraps at all when Width is 0.

Members

  • ChDir – changes the current directory or folder
  • ChDrive – changes the current drive
  • CurDir – returns the current path
  • Dir – returns the name of a file, directory, folder, or volume label that matches a pattern
  • EOF – returns whether the end of a file opened for Random or sequential Input has been reached
  • FileAttr – returns the file mode for files opened with the Open statement
  • FileCopy – copies a file
  • FileDateTime – returns the date and time when a file was created or last modified
  • FileLen – returns the length of a file in bytes
  • FreeFile – returns the next file number available for use by the Open statement
  • GetAttr – returns the attributes of a file or directory
  • Input, Input$ – reads a fixed number of characters from an open sequential file
  • InputB, InputB$ – reads a fixed number of bytes from an open sequential file
  • Kill – deletes files from a disk
  • Loc – returns the current read/write position within an open file
  • LOF – returns the size, in bytes, of an open file
  • MkDir – creates a new directory or folder
  • Reset – closes all disk files opened by using the Open statement
  • RmDir – removes an existing directory or folder
  • Seek – returns or sets the read/write position within an open file
  • SetAttr – sets attribute information for a file
  • Width – sets the line width for a sequential output file