Windows filepath converted to Linux filepath

There would be a way to do both replacements at once using sed, but it's not necessary.

Here's how I would solve this problem:

1. Put filenames in array
2. Iterate over array

filenames=(
  'C:\Users\abcd\Downloads\testingFile.log'
  # ... add more here ...
)

for f in "${filenames[@]}"; do
  f="${f/C://c}"
  f="${f//\\//}"
  echo "$f"
done

If you want to put the output into an array instead of printing, replace the echo line with an assignment:

  filenames_out+=( "$f" )

If it's something you want to do many times, then why not create a little shell function?

win2lin () { f="${1/C://c}"; printf '%s\n' "${f//\\//}"; }

$ file='C:\Users\abcd\Downloads\testingFile.log'
$ win2lin "$file"
/c/Users/abcd/Downloads/testingFile.log
$ 
$ file='C:\Users\pqrs\Documents\foobar'
$ win2lin "$file"
/c/Users/pqrs/Documents/foobar

You would be able to achieve this in one line using sed

file="$(echo "$file" | sed -r -e 's|^C:|/c|' -e 's|\\|/|g')"

Note the two patterns must remain separate nonetheless as the matches are replaced by different substitutions.