User Commands                                            cksum(1)



NAME
     cksum - write file checksums and sizes

SYNOPSIS
  /usr/bin/cksum
     /usr/bin/cksum [ options ] [file...]
 
  ksh93
     cksum [ options ] [file...]

DESCRIPTION
     The cksum command and ksh93 built-in command "cksum" lists
     the checksum, and for most methods the block count, for each
     file argument. The standard input is read if there are no
     file arguments.

     The default method is "cksum" which calculates and writes
     to standard output a cyclic redundancy check (CRC) for each
     input file, and also writes to standard output the number
     of octets in each file.

     For each file processed successfully the cksum method will 
     write in the following format:

          "%u %d %s\n" <checksum>, <# of octets>, <path name>
     Method names consist of a leading identifier and 0 or more
     options separated by -.

     The CRC used is based on the polynomial used for  CRC  error
     checking in the referenced Ethernet standard.

     The encoding for the CRC checksum is defined by the generat-
     ing polynomial:

     G(x) = x**32 + x**26 + x**23 + x**22+ x**16 + x**12 + x**11
     + x**10 + x**8 + x**7 + x**5 + x**4 + x**2 + x + 1

     Mathematically, the CRC value corresponding to a given  file
     is defined by the following procedure:
     1.  The n bits to be evaluated  are  considered  to  be  the
         coefficients  of  a mod 2 polynomial M(x) of degree n-1.
         These n bits are the bits from the file, with  the  most
         significant  bit  being  the most significant bit of the
         first octet of the file and the last bit being the least
         significant bit of the last octet, padded with zero bits
         (if necessary) to achieve an integral number of  octets,
         followed  by  one or more octets representing the length
         of the file as a binary value, least  significant  octet
         first.   The   smallest  number  of  octets  capable  of
         representing this integer is used.

     2.  M(x) is multiplied by x**32 (that is,  shifted  left  32
         bits)  and divided by G(x) using mod 2 division, produc-
         ing a remainder R(x) of degree < 31.

     3.  The coefficients of R(x) are considered to be  a  32-bit
         sequence.

     4.  The bit sequence is complemented and the result  is  the
         CRC.


     getconf PATH_RESOLVE determines how symbolic links are
     handled. This can be explicitly overridden by the --logical,
     --metaphysical, and --physical options below. PATH_RESOLVE
     can be one of:
       logical
             Follow all symbolic links.
       metaphysical
             Follow command argument symbolic links, otherwise
             don't follow.
       physical
             Don't follow symbolic links.

OPTIONS
     The following options are supported by /usr/bin/cksum
  -a, --all       List the checksum for all files. Use with
                  --total to list both individual and total
                  checksums and block counts.
  -b, --binary    Read files in binary mode. This is the
                  default.
  -B, --scale=scale
                  Block count scale (bytes per block) override
                  for methods that include size in the output.
                  The default is method specific.
  -c, --check     Each file is interpreted as the output from a
                  previous sum. If --header or --permissions was
                  specified in the previous sum then the
                  checksum method is automatically determined,
                  otherwise --method must be specified. The
                  listed checksum is compared with the current
                  value and a warning is issued for each file
                  that does not match. If file was generated by
                  --permissions then the file mode, user and
                  group are also checked. Empty lines, lines
                  starting with #<space>, or the line # are
                  ignored. Lines containing no blanks are
                  interpreted as [no]name[=value] options:
                    method=name
                          Checksum method to apply to subsequent
                          lines.
                    permissions
                          Subsequent lines were generated with
                          --permissions.
  -h, --header    Print the checksum method as the first output
                  line. Used with --check and --permissions.
  -l, --list      Each file is interpreted as a list of files,
                  one per line, that is checksummed.
  -p, --permissions
                  If --check is not specified then list the file
                  mode, user and group between the checksum and
                  path. User and group matching the caller are
                  output as -. If --check is specified then the
                  mode, user and group for each path in file are
                  updated if necessary to match those in file. A
                  warning is printed on the standard error for
                  each changed file.
  -R, --recursive Recursively checksum the contents of
                  directories.
  -t, --total     List only the total checksum and block count
                  of all files. --all --total lists each
                  checksum and the total. The total checksum and
                  block count may be different from the checksum
                  and block count of the catenation of all files
                  due to partial blocks that may occur when the
                  files are treated separately.
  -T, --text      Read files in text mode (i.e., treat \r\n as
                  \n).
  -w, --warn      Warn about invalid --check lines. On by
                  default; -w means --nowarn.
  -x, --method|algorithm=method
                 Specifies the checksum method to apply. Parenthesized method options are readonly implementation
                 details.
                   att|sys5|s5|default
                         The system 5 release 4 checksum. This is the default for sum when getconf UNIVERSE is att.
                         This is the only true sum; all of the other methods are order dependent.
                   ast4|32x4|tw
                         The ast 128 bit PRNG hash generated by catenating 4 separate 32 bit PNRG hashes. The block
                         count is not printed.
                   bsd|ucb
                         The BSD checksum.
                   crc   32 bit CRC (cyclic redundancy check).
                           polynomial=mask
                                 The 32 bit crc polynomial bitmask with implicit bit 32. The default value is
                                 0xedb88320.
                           done[=number]
                                 XOR the final crc value with number. 0xffffffff is used if number is omitted. The
                                 option value may be omitted. The default value is 0.
                           init[=number]
                                 The initial crc value. 0xffffffff is used if number is omitted. The option value may
                                 be omitted. The default value is 0.
                           rotate
                                 XOR each input character with the high order crc byte (instead of the low order).
                           size[=number]
                                 Include the total number of bytes in the crc. number, if specified, is first XOR'd
                                 into the size. The option value may be omitted. The default value is 0.
                   prng  32 bit PRNG (pseudo random number generator) hash.
                           mpy=number
                                 The 32 bit PRNG multiplier. The default value is 0x01000193.
                           add=number
                                 The 32 bit PRNG addend. The default value is 0.
                           init[=number]
                                 The PRNG initial value. 0xffffffff is used if number is omitted. The option value may
                                 be omitted. The default value is 0x811c9dc5.
                   md4|MD4
                         RFC1320 MD4 message digest. Cryptographically weak. The block count is not printed.
                           (version)
                                 md4 (solaris -lmd) 2005-07-26
                   md5|MD5
                         RFC1321 MD5 message digest. Cryptographically weak. The block count is not printed.
                           (version)
                                 md5 (solaris -lmd) 2005-07-26
                   sha1|SHA1|sha-1|SHA-1
                         RFC3174 / FIPS 180-1 SHA-1 secure hash algorithm 1. Cryptographically weak. The block count
                         is not printed.
                           (version)
                                 sha1 (solaris -lmd) 2005-07-26
                   sha256|sha-256|SHA256|SHA-256
                         FIPS 180-2 SHA256 secure hash algorithm. The block count is not printed.
                           (version)
                                 sha256 (solaris -lmd) 2005-07-26
                   sha384|sha-384|SHA384|SHA-384
                         FIPS 180-2 SHA384 secure hash algorithm. The block count is not printed.
                           (version)
                                 sha384 (solaris -lmd) 2005-07-26
                   sha512|sha-512|SHA512|SHA-512
                         FIPS 180-2 SHA512 secure hash algorithm. The block count is not printed.
                           (version)
                                 sha512 (solaris -lmd) 2005-07-26
                   posix|cksum|std|standard
                         The posix 1003.2-1992 32 bit crc checksum. This is the default cksum(1) method. Shorthand for
                         crc-0x04c11db7-rotate-done-size.
                   zip   The zip(1) crc. Shorthand for crc-0xedb88320-init-done.
                   fddi  The FDDI crc. Shorthand for crc-0xedb88320-size=0xcc55cc55.
                   fnv|fnv1
                         The Fowler-Noll-Vo 32 bit PRNG hash with non-zero initializer (FNV-1). Shorthand for
                         prng-0x01000193-init=0x811c9dc5.
                   ast|strsum
                         The ast strsum(3) PRNG hash. Shorthand for prng-0x63c63cd9-add=0x9c39c33d.
  -L, --logical|follow
                  Follow symbolic links when traversing
                  directories. The default is determined by
                  getconf PATH_RESOLVE.
  -H, --metaphysical
                  Follow command argument symbolic links,
                  otherwise don't follow symbolic links when
                  traversing directories. The default is
                  determined by getconf PATH_RESOLVE.
  -P, --physical  Don't follow symbolic links when traversing
                  directories. The default is determined by
                  getconf PATH_RESOLVE.
  -r, --bsd       Equivalent to --method=bsd --scale=512 for
                  compatibility with other sum(1)
                  implementations.
  -s, --sysv      Equivalent ti --method=sys5 for for
                  compatibility with other sum(1)
                  implementations.
  -S, --silent|status
                  No output for --check; 0 exit status means all
                  sums matched, non-0 means at least one sum
                  failed to match. Ignored for --permissions.
  --man, --html, --nroff
                  Prints builtin manual page in either plain
                  text, HTML or nroff format.
  --help          Prints basic help information
  --version       Prints version information


OPERANDS
     The following operand is supported:

     file     A path name of a file to be  checked.  If  no  file
              operands are specified, the standard input is used.



USAGE
     The cksum command is typically used  to  quickly  compare  a
     suspect  file against a trusted version of the same, such as
     to ensure that files transmitted  over  noisy  media  arrive
     intact.  However, the CRC comparison cannot be considered
     cryptographically secure. The chances of a damaged file
     producing  the  same CRC as the original are astronomically
     small; deliberate deception is difficult, but probably not
     impossible. In such cases a cryptographically stronger hash
     method (such as "sha512") is recommended.

     Although input files to cksum can be any type,  the  results
     need not be what would be expected on character special dev-
     ice files. Since this document does not  specify  the  block
     size  used  when doing input, checksums of character special
     files need not process all of the data in those files.

     The CRC algorithm is expressed in terms of a bitstream
     divided into octets. If a file is transmitted between two
     systems and undergoes any data transformation (such as
     moving  8-bit characters into 9-bit bytes or changing
     "Little Endian" byte ordering to "Big Endian"), identical
     CRC  values  cannot  be expected.  Implementations
     performing  such transformations may extend cksum to handle
     such situations.

     See largefile(5) for the  description  of  the  behavior  of
     cksum  when  encountering  files  greater than or equal to 2
     Gbyte ( 2**31 bytes).

ENVIRONMENT VARIABLES
     See environ(5) for descriptions of the following environment
     variables  that affect the execution of cksum: LANG, LC_ALL,
     LC_CTYPE, LC_MESSAGES, and NLSPATH.

EXIT STATUS
     The following exit values are returned:

     0        All files were processed successfully.

     >0       An error occurred.



ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcsu                     |
    |_____________________________|_____________________________|
    | Interface Stability         | Standard                    |
    |_____________________________|_____________________________|

    This command conforms to IEEE Std 1003.1-2008.

SEE ALSO
     digest(1), ksh93(1), sum(1), bart(1M), attributes(5),
     environ(5), largefile(5), standards(5),
     http://www.opengroup.org/onlinepubs/9699919799/utilities/cksum.html


SunOS 5.10           Last change: 1 Feb 1995                    3