Add a progressive identifier to file names with embedded ISO 8601 dates.

rename_files_iso8601_with_progressive_id.ps1

#
# rename a bunch of files as follows
#
#     YYYY-MM-DD_NAME.EXT ==> YYYY-MM-DD_nnnn_NAME.EXT
#
# where nnnn is a progressive identifier
#


# initialize the progressive identifier
$id = 0;

# for each file in the local path
Get-ChildItem -name |% {

  # old filename is in the form YYYY-MM-DD_NAME.EXT (e.g. 1982-04-26_foobar.txt)
  $old_filename = $_;

  # extract the date part (e.g., 1982-04-26)
  $trailing = $($old_filename.Substring(0, 10));

  # extract the suffix part (e.g.. foobar.txt);
  $leading = $_.Substring(11);

  # build up the new filename (e.g. 1982-04-26_0123_foobar.txt)
  $new_filename = "{0}_{1:0000}_{2}" -f $trailing, $id, $leading

  # rename the file
  move $old_filename $new_filename;
  
  $id += 1;
}