How do I check the downloaded image of R to ensure it has not been tampered with or corrupted during the mirroring process?

When I recently downloaded the latest version of R to a new MacBook Pro, the web page at the CRAN at UC Berkeley for MAC OS said to "check开发者_StackOverflow社区 the MD5 checksum of the downloaded image to ensure that it has not been tampered with or corrupted during the mirroring process."

It says, "For example, type md5 R-2.13.0.pkg in the Terminal application to print the MD5 checksum for the R-2.13.0.pkg image."

The text in quotes I copied from: http://cran.cnr.berkeley.edu/ on June 27, 2011.

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1. Open up a Terminal Window (Hit Apple Key + Space, type Terminal, hit enter)
2. When the window is ready, type: md5

3. Find the R--2.13.0.pkg file you downloaded; drag it into the terminal window. This will simply copy the file path into terminal, so you will have something like:

   chris:~ chris$ md5 /Users/chris/Downloads/R-2.13.0.pkg
   

4) Hit return, you will get back something like:

chris:~ chris$ babd21ebbc9cbe05ff713aaaa694eff7

Now just check that number against the original, which can be found on the R website in super-tiny subscript below the download link