#! /usr/bin/env bash
#
# Given one or more filenames, output the first line of each file and return 0.
# If a filename does not correspond to a regular file, or if this script
# lacks read permission to the file, then output a blank line.
#
# first-line <file> ...

for fname in "$@"; do
    [ -s "$fname" ] && head -n 1 "$fname" 2>/dev/null || echo
done