(coreutils.info.gz) md5sum invocation

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(coreutils.info.gz) cksum invocation

(coreutils.info.gz) Summarizing files

(coreutils.info.gz) sha1sum invocation

 
 6.4 'md5sum': Print or check MD5 digests
 ========================================
 
 'md5sum' computes a 128-bit checksum (or "fingerprint" or
 "message-digest") for each specified FILE.
 
    Note: The MD5 digest is more reliable than a simple CRC (provided by
 the 'cksum' command) for detecting accidental file corruption, as the
 chances of accidentally having two files with identical MD5 are
 vanishingly small.  However, it should not be considered secure against
 malicious tampering: although finding a file with a given MD5
 fingerprint is considered infeasible at the moment, it is known how to
 modify certain files, including digital certificates, so that they
 appear valid when signed with an MD5 digest.  For more secure hashes,
 consider using SHA-2.   sha2 utilities.
 
    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.  Synopsis:
 
      md5sum [OPTION]... [FILE]...
 
    For each FILE, 'md5sum' outputs the MD5 checksum, a flag indicating
 binary or text input mode, and the file name.  If FILE contains a
 backslash or newline, the line is started with a backslash, and each
 problematic character in the file name is escaped with a backslash,
 making the output unambiguous even in the presence of arbitrary file
 names.  If FILE is omitted or specified as '-', standard input is read.
 
    The program accepts the following options.  Also see  Common
 options.
 
 '-b'
 '--binary'
      Treat each input file as binary, by reading it in binary mode and
      outputting a '*' flag.  This is the inverse of '--text'.  On
      systems like GNU that do not distinguish between binary and text
      files, this option merely flags each input mode as binary: the MD5
      checksum is unaffected.  This option is the default on systems like
      MS-DOS that distinguish between binary and text files, except for
      reading standard input when standard input is a terminal.
 
 '-c'
 '--check'
      Read file names and checksum information (not data) from each FILE
      (or from stdin if no FILE was specified) and report whether the
      checksums match the contents of the named files.  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 file
      name.  Binary mode is indicated with '*', text with ' ' (space).
      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 file name, 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.
 
 '--quiet'
      This option is useful only when verifying checksums.  When
      verifying checksums, don't generate an 'OK' message per
      successfully checked file.  Files that fail the verification are
      reported in the default one-line-per-file format.  If there is any
      checksum mismatch, print a warning summarizing the failures to
      standard error.
 
 '--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.
 
 '--tag'
      Output BSD style checksums, which indicate the checksum algorithm
      used.  As a GNU extension, file names with problematic characters
      are escaped as described above, with the same escaping indicator of
      '\' at the start of the line, being used.  The '--tag' option
      implies binary mode, and is disallowed with '--text' mode as
      supporting that would unnecessarily complicate the output format,
      while providing little benefit.
 
 '-t'
 '--text'
      Treat each input file as text, by reading it in text mode and
      outputting a ' ' flag.  This is the inverse of '--binary'.  This
      option is the default on systems like GNU that do not distinguish
      between binary and text files.  On other systems, it is the default
      for reading standard input when standard input is a terminal.  This
      mode is never defaulted to if '--tag' is used.
 
 '-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.
 
 '--strict'
      When verifying checksums, if one or more input line is invalid,
      exit nonzero after all warnings have been issued.
 
    An exit status of zero indicates success, and a nonzero value
 indicates failure.
 

Info Catalog

(coreutils.info.gz) cksum invocation

(coreutils.info.gz) Summarizing files

(coreutils.info.gz) sha1sum invocation