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Top Forums Shell Programming and Scripting Different ways to check a file Post 303010662 by rovf on Friday 5th of January 2018 03:12:58 AM
Old 01-05-2018
Since you are mentioning cksum, I assume that you mean the CRC checksum.

Look at this article for a Pure-Perl implementation:

Perl-only CRC32 function (without C code)

Make sure that you don't mix the CRC calculation by cksum and your Perl implementation. If you go for the Perl way, use this one consistently.
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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This command is likely to be withdrawn from X/Open standards.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)
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