Trouble verifying md5 checksums created on Windows with Linux

Question

Verifiying checksums inside a file usually works like this using Linux and md5sum.

    md5sum -c file.md5

However, using it like this on a Windows file reveals errors, that took me a long while to figure out. The first error was easy: Windows uses backslash instead of slash and different line endings. This can be fixed!

    sed 's/\r$//' file.md5 | sed 's_\\_/_g' | md5sum -c

The first sed takes care of the line endings and the second one of the backslashes.
And while this does solve the major issue, it always ignores the first line of the file, saying unhelpfully at the very end:

md5sum: WARNING: 1 line is improperly formatted

Switching lines around doesn't change this. The first line of the file is always ignored.

Answer 1

I finally found the answer after noticing that copying the entire content into a new file does not produce this error.

So it turns out that in Windows the file has some binary characters in front that are not shown in a text editor, but are interpreted by md5sum.

So the solution is then to get rid of these:

 sed 's/\r$//' file.md5 | sed 's_\\_/_g' | sed -e '1s/^.//' | md5sum -c

The third sed removes the first binary blob, finally enabling me to check md5 files generated on Windows!

And because this has been a major ordeal that I didn't find much help online for, I've decided to share it with the world.