File: coreutils.info,  Node: md5sum invocation,  Prev: cksum invocation,  Up: Summarizing files

6.4 `md5sum': Print or check message-digests
============================================

`md5sum' computes a 128-bit checksum (or "fingerprint" or
"message-digest") for each specified FILE.  If a FILE is specified as
`-' or if no files are given `md5sum' computes the checksum for the
standard input.  `md5sum' can also determine whether a file and
checksum are consistent. Synopses:

     md5sum [OPTION]... [FILE]...
     md5sum [OPTION]... --check [FILE]

   For each FILE, `md5sum' outputs the MD5 checksum, a flag indicating
a binary or text input file, and the filename.  If FILE is omitted or
specified as `-', standard input is read.

   The program accepts the following options.  Also see *Note Common
options::.

`-b'
`--binary'
     Treat all input files as binary.  This option has no effect on Unix
     systems, since they don't distinguish between binary and text
     files.  This option is useful on systems that have different
     internal and external character representations.  On MS-DOS and
     MS-Windows, this is the default.

`-c'
`--check'
     Read filenames and checksum information from the single FILE (or
     from stdin if no FILE was specified) and report whether each named
     file and the corresponding checksum data are consistent.  The
     input to this mode of `md5sum' is usually the output of a prior,
     checksum-generating run of `md5sum'.  Each valid line of input
     consists of an MD5 checksum, a binary/text flag, and then a
     filename.  Binary files are marked with `*', text with ` '.  For
     each such line, `md5sum' reads the named file and computes its MD5
     checksum.  Then, if the computed message digest does not match the
     one on the line with the filename, the file is noted as having
     failed the test.  Otherwise, the file passes the test.  By
     default, for each valid line, one line is written to standard
     output indicating whether the named file passed the test.  After
     all checks have been performed, if there were any failures, a
     warning is issued to standard error.  Use the `--status' option to
     inhibit that output.  If any listed file cannot be opened or read,
     if any valid line has an MD5 checksum inconsistent with the
     associated file, or if no valid line is found, `md5sum' exits with
     nonzero status.  Otherwise, it exits successfully.

`--status'
     This option is useful only when verifying checksums.  When
     verifying checksums, don't generate the default one-line-per-file
     diagnostic and don't output the warning summarizing any failures.
     Failures to open or read a file still evoke individual diagnostics
     to standard error.  If all listed files are readable and are
     consistent with the associated MD5 checksums, exit successfully.
     Otherwise exit with a status code indicating there was a failure.

`-t'
`--text'
     Treat all input files as text files.  This is the reverse of
     `--binary'.

`-w'
`--warn'
     When verifying checksums, warn about improperly formatted MD5
     checksum lines.  This option is useful only if all but a few lines
     in the checked input are valid.


   An exit status of zero indicates success, and a nonzero value
indicates failure.