07-06-2009
Checksums verify the byte-by-byte content of files. Some are considered better than others.
You should use an already written routine, commonly available checksum or hashing command line utilities:
cksum
md5
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cksum(1) General Commands Manual cksum(1)
NAME
cksum - print file checksum and sizes
SYNOPSIS
[file ...]
DESCRIPTION
The command calculates and prints to standard output a checksum for each named file, the number of octets in the file and the filename.
uses a portable algorithm based on a 32-bit Cyclic Redundancy Check. This algorithm finds a broader spectrum of errors than the 16-bit
algorithms used by (see sum(1)). The CRC is the sum of the following expressions, where x is each byte of the file.
+ x^8 + x^7 + x^5 + x^4 + x^2 + x^1 + x^0 x26 + x23 + x22 + x16 + x12 + x11 + x10 + x7 + x5 + x4 + x2 + x1 + x0
The results of the calculation are truncated to a 32-bit value. The number of bytes in the file is also printed.
Standard input is used if no file names are given.
is typically used to verify data integrity when copying files between systems.
EXTERNAL INFLUENCES
Environment Variables
determines the locale to use for the locale categories when both and the corresponding environment variable (beginning with do not specify
a locale. If is not set or is set to the empty string, a default of "C" (see lang(5)) is used.
determines the locale for interpretation of sequences of bytes of text data as characters (e.g., single- verses multibyte characters in
arguments and input files).
determines the language in which messages are displayed.
If any internationalization variable contains an invalid setting, behaves as if all internationalization variables are set to "C". See
environ(5).
RETURN VALUE
Upon completion, returns one of the following values:
All files were processed successfully.
One or more files could not be read or another error occurred.
If an inaccessible file is encountered, continues processing any remaining files, but the final exit status is affected.
SEE ALSO
sum(1), wc(1).
STANDARDS CONFORMANCE
cksum(1)