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I use OS X and have several checksum files that are generated from different external harddisks.

If the checksum files are in the same location as the files to check then I can simply run eg.:

shasum -c sums.sha1

But in my case sums.sha1 is located in ~/Desktop/sums.sha1 and the files to verify are in /Volumes/fr-ubb-1 (external drive, read only).

I understand that it's not possible to pass a location parameter to shasum. What's the best practice to run the verification of my checksum file with files in a different location?

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Run it from the directory containing the files to check, and give it the full path to the checksum file:

cd /Volumes/fr-ubb-1
shasum -c ~/Desktop/sums.sha1

This works with most (perhaps all) checksum verification tools, not just shasum.

  • It does not, unfortunately, work with md5 on macOS as it has no verification capability (that I can see). – Kusalananda Oct 4 '17 at 10:23
  • @Kusalananda isn’t there an md5sum on macOS? At least some macOS users have it but I don’t know whether it came with the OS or was installed separately. – Stephen Kitt Oct 4 '17 at 11:22
  • That's from GNU coreutils, which obviously can be installed on macOS, but isn't by default. md5 is the BSD variation on the same theme. md5 supports -c on other BSD systems (NetBSD and OpenBSD, but it means something else on FreeBSD). My guess is that macOS is using an older version of it. – Kusalananda Oct 4 '17 at 11:22
  • @Kusalananda OK, thanks for the clarification. I’m not familiar with modern BSD, but yes, macOS does tend to have old versions of the BSD tools... – Stephen Kitt Oct 4 '17 at 11:26
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Or modify the content of the sums.md5 to include absolute path to files.

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