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cksum(1)                         User Commands                        cksum(1)

       cksum - write file checksums and sizes

       /usr/bin/cksum [file...]

       The  cksum  command  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 writes in the
       following format:

       "%u %d %s\n" <checksum>, <# of octets>, <path name>

       If no file operand was specified, the path name and its  leading  space
       is omitted.

       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 generating  polyno‐

         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  coeffi‐
                  cients  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 capa‐
                  ble 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,  producing  a
                  remainder R(x) of degree ≤ 31.

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

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

       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.

       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, this comparison
       cannot be considered cryptographically secure. When compatibility  with
       existing  cksum  usage or values is not required, the digest(1) command
       is recommended instead, as it provides more  modern  and  secure  algo‐

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

       The 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 val‐
       ues cannot be expected. Implementations performing such transformations
       can extend cksum to handle such situations.

       See environ(7) for descriptions of the following environment  variables
       that  affect  the  execution  of cksum: LANG, LC_ALL, LC_CTYPE, LC_MES‐
       SAGES, and NLSPATH.

       The following exit values are returned:

       0      All files were processed successfully.

       > 0    An error occurred.

       See attributes(7) for descriptions of the following attributes:

       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE VALUE _ Availabilitysystem/core-os _ Interface StabilityCommit‐
       ted _ StandardSee standards(7).

       digest(1), sum(1), attributes(7), environ(7), standards(7), bart(8)

Oracle Solaris 11.4               28 Apr 2020                         cksum(1)
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