Using Fastsum Command Line Edition

This page is designed to introduce you to using FastSum Command Line Edition – the message digest utility.

FastSum generates, stores and verifies message digests (digital signatures) using the MD5 algorithm. This program can be useful for file comparison, and detection of file corruption and tampering. This page contains the following chapters:

Using Command Line Syntax
Using FastSum to Create a CD\DVD That Can be Verified in Future

Using Command Line Syntax

FSUM [Path] [File | /T:Type] [/C:File] [/V] [/O] [/R]


Specifies path to the source files and may address to a single file, folder or folder with included files mask that can be enumerated through semicolon.

Note: Paths that contain spaces must be enclosed within quotation marks.


FSUM "D:\My Docs\Report"

Calculates checksums and prints it on the screen.

FSUM "D:\My Docs\Report\*.xls;*.doc"

Same as above but calculates only .xls and .doc files.


Specifies the path to the file where checksums will be stored or taken from, depending on the mode.

If the path is specified as relative (like \Docs\March) it will be transformed into absolute, considering the current path (C:\Users\Docs\March). If this parameter is not defined in calculation mode checksums are printed on the screen. In verification mode FastSum is trying to find the checksum file with the current folder name. In case of success our software loads previously computed values from this file and then verifies the files listed in a checksum file.

Note: /T:Type parameter helps to process a lot of files in typical cases (See below).


FSUM "D:\My Docs\Report\march.xls" march.md5

Results will be written to the march.md5 in current folder.

FSUM "D:\My Docs\Report\march.xls" "D:\My Docs\Report\march.md5"

All paths are absolute.


It is a parameter-helper that defines the position of checksum files, for most typical cases, so that you do not have to type it all by hand.

The File parameter takes up a different meaning and allows setting custom extension of checksum files. Type parameter can be one of the following values:

E - Creates checksum files for each file and creates file names by combining the source file name and checksum file extension (MyDocument.doc.md5 for MyDocument.doc). You can define custom extension for checksum files by using File option:

FSUM c:\temp .lst /t:e

Replaces the default .md5 extension with the .lst

R - Creates a list of all files and their digital signatures in one file placing it in the path root.

- Generates one file for each folder. This mode is a compromise between speed and convenience.

You can define custom extensions or different filenames for checksum files by using File option, see the table below:

  /T:E (Each) /T:R (One per root) /T:F (One per folder)
Custom extention (.md5)
Custom filename (checksums.md5)

Note: During scanning and files list formation processes, before checksum calculation, FastSum ignores files with .md5 extension to preclude their repeated calculation. Therefore, we highly recommend to not changing the default extension.


FSUM "D:\My Docs\Report" /T:E

Calculates and stores checksums for each file.


Creates a list of changed files where each string is an absolute file path. This parameter is very useful for transmitting checksum verification results to another software program and is used only with /V ption.

Note: The list is created only when any files have changed. If the file already exists it will be overwritten without any warning and it is independent from the /O option.


Verifies the checksums that have been stored during the last check and writes the result to the standard output.


Overwrites the existing checksum files or asks for a permission to do it on the fly in case of no – /O specification while detecting a large amount of file-candidates for overwriting.


Recursively scans all subfolders within a directory specified by Path parameter.


Marks checksum files with hidden attribute.


Info parameter includes additional information into the checksum file. Any combination of the following attributes is acceptable for this parameter. D - Date, T - Time, U - User, H - Host, R - Root path, E - Errors.

Example: /I:DTUHRE


Using FastSum to Create a CD\DVD That Can be Verified in Future

Before you burn the disc:

  • Copy all your files that you want to burn on a disk to one folder, for example: d:\cd
  • Run Command Prompt by typing “cmd” in Run dialog from the Start menu or chousing the Command Prompt from Accessories.
  • Type fsum d:\cd /t:r /r in the Command Prompt.

When FastSum has calculated the checksums it creates a specific list on: d:\cd\cd.md5. Now you can burn the contents of the folder on your disk. When you want to check the integrity of the disk, let us assume that it is disk W:\, type fsum w:\ w:\cd.md5 /r /v

Free Download! The two integrity checkers based on cryptographic approved MD5 checksum algorithm in the one package!