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Right now I have these commands:

my_dir="$HOME/foo/bar"; rm -rf "$my_dir/WebstormProjects/"; rsync -r --exclude=".git" --exclude="node_modules" "$HOME/WebstormProjects/" "$my_dir/WebstormProjects/"

instead of removing everything in "$my_dir/WebstormProjects/" and then copying over, I am looking to use rsync such that it will only overwrite files in "$my_dir/WebstormProjects/" if the files in "$HOME/WebstormProjects/" are newer. So something like this:

my_dir="$HOME/foo/bar"; rsync -r --newer --exclude=".git" --exclude="node_modules" "$HOME/WebstormProjects/" "$my_dir/WebstormProjects/"

is it possible to copy files only if they are newer than the destination files?

I did some reading: https://www.tecmint.com/sync-new-changed-modified-files-rsync-linux/

it says:

By default, rsync only copies new or changed files from a source to destination...

I assume it does this by comparing relative file paths? Files with the same path/name are considered to be the same?

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  • Keep reading; rsync will compare timestamps as well as hashing the files. See serverfault.com/a/211083 Commented Aug 14, 2018 at 0:22

1 Answer 1

Reset to default
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This is the rsync default behavior. It checks file size and last modification size.

If you want it to use checksums instead, use the -c or --checksum option (same effect). The man page is here and describes the option, also of interest might be --size-only

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  • 2
    Yeah checksum seems like the more accurate approach since we usually care about file contents.. Commented Aug 14, 2018 at 3:55
  • @AlexanderMills Yes, it is more accurate. Just be aware that for large files it can get very slow (since it has to read and run a one-way hash on the ENTIRE file). If the size, name, and modified time of a file are all the same, the file has probably not updated. Unless you run into or really anticipate a problem with those causing issues you're probably just better off using rsync's sane defaults. Happy coding! Commented Aug 14, 2018 at 4:13
  • Ah yes, you are probably right Commented Aug 14, 2018 at 21:15
  • @alexmherrmann I believe that rsync checks the file size first. If the size has changed, then it skips the checksum hash, rightly assuming that the checksum has also changed. Commented Feb 4 at 19:52

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