SED: Delete first N lines of a file

# Remove the first 10 lines and write to a new file:
sed '1,10d' your_file.txt > output_file.txt

# to edit the file in place, use the -i option:
sed -i '1,10d' your_file.txt

# to make a backup of the original file:
sed -i.bak '1,10d' your_file.txt

# On MAcOS (BSD) the behaviour differs - an empty string is required after -i:
sed -i '' '1,10d' your_file.txt

# or to backup (notice the space after -1 and before .bak)
sed -i .bak '1,10d' your_file.txt

# One-liner to process all files in a directory, checking for OS type, and making backups:
find . -type f -exec bash -c '
  if [[ "$OSTYPE" == "darwin"* ]]; then 
    sed -i .bak "1,10d" "$0"; 
  else 
    sed -i.bak "1,10d" "$0"; 
  fi
' {} \;