#!/bin/bash
OUT=/tmp/outfile.txt
IN=/my_in_file.txt

sed $IN << SED_SCRIPT
    s/a/1/g
    s/test/full/g

SED_SCRIPT
> $OUT;

sed -f - "$IN" > "$OUT" << SED_SCRIPT
    s/a/1/g
    s/test/full/g
SED_SCRIPT

IN=my_in_file.txt
OUT=/dev/stdout

sed -s 's/A/B/' < $IN > $OUT
sed -s 's/A/B/' > $OUT < $IN

sed -s 's/in/out/' <<< input > $OUT