


sum(n)               Cyclic Redundancy Checks              sum(n)


______________________________________________________________________________

NAME
       sum - Calculate a sum(1) compatible checksum

SYNOPSIS
       package require Tcl  8.2

       package require sum  ?1.1.0?

       ::crc::sum  ?-bsd  | -sysv? ?-format fmt? ?-chunksize size? [ -filename
       file | -channel chan | string ]

_________________________________________________________________

DESCRIPTION
       This package provides a Tcl-only implementation of the  sum(1)  command
       which  calculates a 16 bit checksum value from the input data.  The BSD
       sum algorithm is used by default but the SysV algorithm is also  avail-
       able.

COMMANDS
       ::crc::sum  ?-bsd  | -sysv? ?-format fmt? ?-chunksize size? [ -filename
       file | -channel chan | string ]
              The  command  takes  string data or a file name or a channel and
              returns a checksum value calculated using the sum(1)  algorithm.
              The  result  is formatted using the format(n) specifier provided
              or as an unsigned integer (%u) by default.


OPTIONS
       -sysv  The SysV algorithm is fairly naive. The byte values  are  summed
              and  any  overflow is discarded. The lowest 16 bits are returned
              as the checksum.  Input with  the  same  content  but  different
              ordering will give the same result.

       -bsd   This algorithm is similar to the SysV version but includes a bit
              rotation step which provides a dependency on the  order  of  the
              data values.

       -filename name
              Return a checksum for the file contents instead of for parameter
              data.

       -channel chan
              Return a checksum for the contents of the specified channel. The
              channel  must  be  open for reading and should be configured for
              binary translation. The channel will no be closed on completion.

       -chunksize size
              Set  the  block size used when reading data from either files or
              channels. This value defaults to 4096.





crc                           1.1.0                             1





sum(n)               Cyclic Redundancy Checks              sum(n)


       -format string
              Return the checksum using an alternative format template.


EXAMPLES
       % crc::sum "Hello, World!"
       37287



       % crc::sum -format 0x%X "Hello, World!"
       0x91A7



       % crc::sum -file sum.tcl
       13392


AUTHORS
       Pat Thoyts

BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will  undoubtedly  contain
       bugs and other problems.  Please report such in the category crc of the
       Tcllib  SF  Trackers  [http://sourceforge.net/tracker/?group_id=12883].
       Please  also  report any ideas for enhancements you may have for either
       package and/or documentation.

SEE ALSO
       cksum(n), crc32(n), sum(1)

KEYWORDS
       checksum, cksum, crc, crc32, cyclic redundancy check,  data  integrity,
       security, sum

CATEGORY
       Hashes, checksums, and encryption

COPYRIGHT
       Copyright (c) 2002, Pat Thoyts <patthoyts@users.sourceforge.net>
















crc                           1.1.0                             2


