You could try

chardet <<<filename

The chardet program can try to guess the encoding of the stream on stdin, and <<< is the mean by which bash use a string as stdin, the same as

echo filename | chardet

For a whole directory content you can use

ls dir | chardet

EDIT

I forgot about the content, but is almost the same:

chardet <filename

or

cat filename | chardet

or for all the files in dir

cat dir/* | chardet