A bash script for trimming extra blank lines. Consecutive blank lines are collapsed into one. Multiple files can be given as arguments at once.

trim

#!/bin/bash

for file in "$@"; do
  TEMP=temp.$RANDOM

  sed "s/\s*$//" "$file" |   # Trim whitespace from ends of lines
  cat -s                 |   # Collapse consecutive blank lines into one
  tr  "\n" "\0"          |   # Replace new line characters with nulls
  sed "s/\x0*$//"        |   # Trim nulls from the end
  tr  "\0" "\n" > "$TEMP"    # Replace nulls with new line characters

  mv -f "$TEMP" "$file"
done