Find and replace string in directory names

This is not a job for find, since there is no recursion involved.

for x in */C/populate.sh; do
  mkdir -- "${x%%/*}$suffix"
  mkdir -- "${x%%/*}$suffix/C"
  cp -p -- "$x" "./${x%%/*}$suffix/C"
done

Remove the -p option to cp if you don't want to preserve the files' modification time.

To generate a random suffix, BSD/Linux mktemp is as portable as it gets.

suffix=$(mktemp -u tmp_XXXXX)

If you want something vaguely random-looking and POSIX-compliant, this gives a string that changes every second and varies from location to location; you can't really do better with only POSIX tools:

suffix=$({ hostname; pwd; date; } |
         cksum | uuencode -m /dev/stdin | awk 'NR==2 {print substr($0,3,5)}')

If you put this code in a makefile, remember to:

• double all $ signs;
• put all the code on one line, using ; instead to separate shell instructions (you can use backslash+newline+tab to put a line break in the makefile, but that sequence is removed to build the shell command);
• start the shell snippet with set -e, so that it aborts if there is any error.

find . -depth -print0 | perl -0lne '
  if ("$_/" =~ m{/Caches(/.*)}s && $1 !~ m{/Snapshots/}) {rmdir $_ or unlink $_}'

If your find doesn't support -print0, you can replace it with -exec printf '%s\0' {} +.

The idea is to print the list of files NUL-terminated (as 0 is the only byte that can't occur in a file path) and use perl's -n with -0 option to run some code for each of those filenames (with $_ set to the filename).

With -depth, files are printed before their parent directory. We remove only files or directories (assuming they are empty which is why it's important to process the list in depth order) if their path contains /Caches/ not followed by /Snapshosts/.