Command: md5sum

  MD5SUM is a Public Domain program used for computing and checking
  cryptographic message digests (or check values) of files.  It was
  written with the Unix philosophy of reading from standard input and
  writing to standard output, and options can be delimited with "-"
  and "/" in this program version.


  md5sum [/TBV] [/C [file]] | [file...]
  md5sum [/?]


  /C           Check message digests (default is generate).
  /[-]V        Enable or disable verbose mode (default is off).
  /[-]L        Enable or disable LFN usage (default is enable if
  /[-]R[num]   Enable or diable recursing (default is off).
               num is a number from 1 to 9 and limits recursion
  /[-]S        Same as /[-]R=].
  /T           Read files in text mode.
  /B           Read files in binary mode (default; overrides /T).
  /M[:|=]mode  Select the digest mode (SHA or MD5).
  /?           Shows the help.
  The input for /C should be a list of message digests and file names
  that is printed on stdout by this program when it generates digests.
  Note that now, both '-' and '/' switches are accepted.
  When checking files, MD5SUM generates no output if the files match
  their fingerprints, unless you also specify the -v switch. If there
  is a problem, it will generate one or more of the following messages:
    MD5SUM.EXE: can't open filename
    MD5SUM.EXE: error reading filename
    MD5SUM.EXE: MD5 check failed for filename
    MD5SUM.EXE: _ of _ file(s) failed MD5 check
    MD5SUM.EXE: no files checked
  The argument for /M should be a digest mode, which could possible be
  SHA, CRC32, SHA256 or MD5, depending on how MD5SUM was compiled.


  If the MD5 message digest "fingerprint" of a file has not changed,
  this is a VERY good indication that the contents of the file has not
  changed. Even if you wanted to change a file in such a way that it
  still had the same MD5 "fingerprint," you probably couldn't do it
  without a lot of supercomputer time (and neither could a bad guy).
  This makes it useful for detection of forgeries, viruses, and just
  plain transmission errors. Note that this is much more powerful than
  a normal CRC, which is good at detecting some kinds of transmission
  errors, but can easily be forged. This is also useful for signing a
  collection of files with a digital signature (using PGP, a PEM
  implementation, or some kind of DSA implementation, for example),
  without having to individually sign each file. Simply create a text
  file with the "fingerprints" of each file you wish to sign, then sign
  that text file.

  To compute the MD5 fingerprint of a text file, simply type
    MD5SUM filename(s)
  "Wild cards" (like * and ?) ARE supported by this program, you can
  also put more than one file name on the command line. Since the
  program is assuming that this is a text file, line endings conventions
  may differ and still result in the same check value.
    MD5SUM filename(s)
  To see the file names displayed while computing "fingerprints,"
  include the -v option, like:
    MD5SUM -v filename(s)
  To write the output to a file instead of just displaying it on the
  screen, use redirection with the ">" character, like:
    MD5SUM -v filename(s) > md5file
  To append the output to an existing file, use two > characters, like:
    MD5SUM -v filename(s) >> md5file

  Sometimes it is nice to add comments to files containing MD5 finger-
  prints. To do this, just edit the files made using the above
  instructions to add in what you want to say. Lines that do not start
  with valid hexadecimal digits are ignored as comments.

  To check all of the files listed in check files as generated above to
  see if they have changed:
    MD5SUM -c md5file
  For a more verbose listing of results (listing file names followed by
  "OK" or "FAILED"), type:
    MD5SUM -cv md5file

  One way to prevent alteration of fingerprint files is to store several
  copies in different secure places, then compare them from time to time.
  Another way is to use a digital signature produced by PGP, some PEM
  implementation, or a DSS implementation. PGP is the most widely used
  digital signature program in the public sector right now.

  MD5SUM supports NLS (national language support).


  md5sum /M:MD5 /V c:\autoexec.bat
    Creates and shows an MD5 fingerprint of autoexec.bat (works with
    CRC32, SHA and SHA256).
  md5sum /M:SHA /R C:\*.* > D:\myhashes.txt
    Creates an SHA fingerprint of all files at C:\ and subdirectories
    and writes it to D:\myhashes.txt. Please note that edit supports
    only 64 KB size, so another editor maybe needed to open the file.
    If you use the same partition for "myhashes.txt" the hash value
    of this file maybe wrong.
  md5sum -cv d:\myhashes.txt
    Checks all listed files and reports files that failed. The amount
    of FAILS is shown at the end, but not path and filename as the
    list runs through very fast.
  md5sum -cv d:\myhashes.txt > report.txt
    Creates a file report.txt. You can open it with an editor and
    use the search function to find "FAILED" and with this path and
    filename of the modified file.

See also:


   Copyright © 2005 Blair Campbell, help version 2023 W. Spiegl.

  This file is derived from the FreeDOS Spec Command HOWTO.
  See the file H2Cpying for copying conditions.