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I am running a script that copy a file from one location to other. In script I am calculating MD5sum using below command of original file and copied file and they are different:

echo -n "file" | md5sum

How come a same file have different MD5sum? Does copy command change something in Linux? I have also checked checksum using cksum filename and it is also coming different.

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    echo -n "file" | md5sum calculates the sum of the string "file", you want cat file | md5sum or just md5sum file Commented Jan 30, 2014 at 12:37

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echo -n "file" | md5sum

You are not calculating the checksum of the file, but of the filename. It is probably different because you are using two different paths (echo -n "/old/path/to/file" | md5sum vs. echo -n "/new/path/to/file" | md5sum).

To calculate the md5sum of the file, use this command:

md5sum file
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  • Thanks Martin.I have one more confusion that if a file is zipped into tgz then untar it. Then the both original and untar file will also have the same checksum or different? Commented Jan 30, 2014 at 12:34
  • If you compare the original file with the zipped tgz file - no, they will not have the same checksum. If you extract the tgz file and compare the extracted file with the original file - yes, they must have the same checksum. Commented Jan 30, 2014 at 12:37
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You can also use http://sourceforge.net/projects/crcsum/?source=directory which provides a cp and mv extended with checksum calculation & verification

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  • Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. Commented Oct 21, 2014 at 13:47

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