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Full Discussion: Understanding a script for sum
Top Forums UNIX for Beginners Questions & Answers Understanding a script for sum Post 303015605 by uniran on Sunday 8th of April 2018 09:41:05 AM
Old 04-08-2018
Quote:
Originally Posted by RudiC
That obviously is a (bourne) shell function. As you don't mention your shell's version, bash assumed.

man bashSmilieuring expansion, the "multiword character" of $1 is lost, and the shell makes up this five item list: 8 8 8 9 9 across which the for loop iterates, resulting in 42 plus x's initial value. Be aware that the x=$1 assignment has nothing to do with the $1 that func() is called with; function get their own set of parameters when called.
And, remove the space in the let assignment.
Thank you, so the x=$1 assignment doesn't serve any noticeable purpose in this script ?

B.In truth, the for loop doesn't iterates just three times for $1 $2 $3 as defined but rather one time for each existed item,total of five iterations in this case ?
 

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LEARN ABOUT MOJAVE

sum

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 available.

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.

       -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								    sum(n)
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