head -c 50 file

cat ${file} | cut -c1-50

cut -c1-50 < "$file"

dd status=none bs=1 count=50 if=${filename}

grep -om1 "^.{50}" ${filename}

(IFS= read -r line <${filename}; echo ${line:0:50})

sed -e 's/^(.{50}).*/1/' yourfile