03-31-2011
The unix cksum utility does use 32-bit CRC's -- it calculates them the same way ethernet checksums are. But there's more than one way to calculate a 32-bit CRC and more than one way to print one -- hexadecimal ff, hexadecimal FF, and decimal 255 are all the same number but different strings -- and your system's endian may differ too. You can't compare cksum's output string against anything but cksum's output string unless you get the implementation
exactly right.
If your system is Tru64, that's a weird one that does some other sort of CRC.
You'll find a normal implementation
here in cksum.c.
Last edited by Corona688; 03-31-2011 at 02:33 PM..
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sum(1) General Commands Manual sum(1)
NAME
sum - print checksum and block or byte count of file(s)
SYNOPSIS
[file ...]
Remarks
is obsolescent and should not be used in new applications that are intended to be portable between systems. Use instead (see cksum(1)).
DESCRIPTION
calculates and prints to standard output a checksum for each named file, and also prints the size of the file in 512 byte blocks, rounded
up.
The default algorithm is a 16-bit sum of the bytes in which overflow is ignored. Alternate algorithms can be selected with the and
options.
Standard input is used if no file names are given.
is typically used to verify data integrity when copying files between systems.
Options
recognizes the following options:
Use an alternate algorithm in which the 16-bit sum is right rotated
with each byte in computing the checksum.
Use the 32-bit cyclical redundancy check (CRC) algorithm used by
RETURN VALUE
returns the following values upon completion:
All files were processed successfully.
One or more files could not be read or some other error occurred.
If an inaccessible file is encountered, continues processing any remaining files, but the final exit status is affected.
DIAGNOSTICS
Read error conditions are indistinguishable from end of file on most devices; check the block or byte count.
WARNINGS
This command is likely to be withdrawn from X/Open standards. Applications using this command might not be portable to other vendors'
platforms. The usage of cksum(1) is recommended.
SEE ALSO
cksum(1), wc(1).
STANDARDS CONFORMANCE
sum(1)