isText

#!/bin/bash
isText() {
  if [[ -f "$1" ]] && file "$1" | grep -q 'text'; then
    return 0
  else
    return 1
  fi
}

# test
ls |
while read; do
  if isText "${REPLY}"; then
    echo "${REPLY} is text"
  else
    echo "${REPLY} isn't text"
  fi
done