Remove BOM (Byte Order Mark) sequence from a file.

bom-killer.sh

#!/usr/bin/env sh

HELP_MESSAGE="Usage: $(basename "$0") <file>
Remove BOM (Byte Order Mark) sequence from a file.

Arguments:
  <file>        Input file to process

Options:
  -h, --help    Show this help message"

BOM_CHAR="$(printf '\357\273\277')"  # EF BB BF in octal

show_help() {
  echo "$HELP_MESSAGE"
  exit 0
}

remove_bom_from_file() {
  input_file="$1"
  output_file="${input_file%.*}-clean.${input_file##*.}"
  sed "1s/^$BOM_CHAR//" "$input_file" > "$output_file"
}

main() {
  [ "$1" = "-h" ] || [ "$1" = "--help" ] && show_help
  [ -z "$1" ] && { echo "Error: Missing input file"; show_help; }
  remove_bom_from_file "$1"
}

main "$@"