Emacs part 26

外部コマンドは、
#! /bin/sh
hexdump -C ${1+"$@"} | head -1 | grep -q "^00000000 ef bb bf"
if [ "$?" = 0 ]; then
echo yes
else
echo no
fi
こんな感じで。

(shell-command-to-string (concat "/foo/bin/bar" (buffer-file-name)))