Learn to read! Verses 15 through 44 are covered here, and he quotes them explicitly. I know your faith in Catholicism blinds you to certain things, but do at least make the attempt.
It just doesn't. So the quote you always post to "prove" St Augustine didn't believe the Eucharist really is His flesh and blood is misapplied. That's just a fact.
You read it again.
"12. “They said therefore unto Him, What shall we do, that we may work the works of God?” For He had said to them, “Labor not for the meat which perisheth, but for that which endureth unto eternal life.” “What shall we do?” they ask; by observing what, shall we be able to fulfill this precept? “Jesus answered and said unto them, This is the work of God, that ye believe on Him whom He has sent.” This is then to eat the meat, not that which perisheth, but that which endureth unto eternal life. To what purpose dost thou make ready teeth and stomach? Believe, and thou hast eaten already. Faith is indeed distinguished from works, even as the apostle says, “that a man is justified by faith without the works of the law:”13 there are works which appear good, without faith in Christ; but they are not good, because they are not referred to that end in which works are good; “for Christ is the end of the law for righteousness to every one that believeth.”14 For that reason, He willeth not to distinguish faith from work, but declared faith itself to be work. For it is that same faith that worketh by love.15 Nor did He say, This is your work; but, “This is the work of God, that ye believe on Him whom He has sent;” so that he who glories, may glory in the Lord. And because He invited them to faith, they, on the other hand, were still asking for signs by which they might believe. See if the Jews do not ask for signs. “They said therefore rate Him, What sign doest thou, that we may see and believe thee? what dost thou work?” Was it a trifle that they were fed with five loaves? They knew this indeed, but they preferred manna from heaven to this food. But the Lord Jesus declared Himself to be such an one, that He was superior to Moses. For Moses dared not say of Himself that He gave, “not the meat which perisheth, but that which endureth to eternal life.” Jesus promised something greater than Moses gave. By Moses indeed was promised a kingdom, and a land flowing with milk and honey, temporal peace, abundance of children, health of body, and all other things, temporal goods indeed, yet in figure spiritual; because in the Old Testament they were promised to the old man. They considered therefore the things promised by Moses, and they considered the things promised by Christ. The former promised a full belly on the earth, but of the meat which perisheth; the latter promised, “not the meat which perisheth, but that which endureth unto eternal life.” They gave attention to Him that promised the more, but just as if they did not yet see Him do greater things. They considered therefore what sort of works Moses had done, and they wished yet some greater works to be done by Him who promised them such great things. What, say they, doest thou, that we may believe thee? And that thou mayest know that they compared those former miracles with this and so judged these miracles which Jesus did as being less; “Our fathers,” say they, “did eat manna in the wilderness.” But what is manna? Perhaps ye despise it. “As it is written, He gave them manna to eat.” By Moses our fathers received bread from heaven, and Moses did not say to them, “Labor for the meat which perisheth not.” Thou promisest “meat which perisheth not, but which endureth to eternal life;” and yet thou workest not such works as Moses did. He gave, not barley loaves, but manna from heaven."
He (St Augustine) is talking here about John 6:28. This is wayyy before the discourse on the need for Jesus' flesh and blood for salvation.
He (St Augustine) is talking here about the need for faith first, because it is faith first in Jesus that truly sustains, ie brings life eternal. Not the food the Jews were seeking. They were seeking another miracle from Jesus not Him himself. This is what St Agustine was saying when he was saying "believe and ye have eaten already". He's saying that we shouldn't look to Jesus to fill our bellies (in other words as Someone who is some kind of heavenly ATM providing us things here on earth), rather He is the source of life itself therefore we must believe in Him first before anything else including seeking after any carnal need or desire.
He (St Augustine along with Jesus) goes on to say: (in the same Tractate)
13. “Then Jesus said unto them, Verily, verily, I say unto you, not Moses gave you bread from heaven, but my Father gave you bread from heaven. For the true bread is He that cometh down from heaven, and giveth life to the world.” The true bread then is He that giveth life to the world; and the same is the meat of which I have spoken a little before,-“Labor not for the meat which perisheth, but for that which endureth unto eernal life.” Therefore, both that manna signified this meat, and all those signs were signs of me. Ye have longed for signs of me; do ye despise Him that was signified? Not Moses then gave bread from heaven: God gives bread. But what bread? Manna, perhaps? No, but the bread which manna signified, namely, the Lord Jesus Himself. My Father giveth you the true bread. “For the bread of God is He that cometh down from heaven, and giveth life to the world Then said they unto Him, Lord, evermore give us this bread.” Like that Samaritan woman, to whom it was said, “Whoso drinketh of this water shall never thirst.” She, immediately understanding it in reference to the body, and wishing to be rid of want, said, “Give me, O Lord, of this water;” in the same manner also these said, “O Lord, give us this bread;” which may refresh us, and yet not fail."
Here we can already see St Augustine stressing the need for Jesus as a heavenly food. However, as has already been pointed out to you, Tractate 26 (starting from paragraph 15 onward) more fully develops this concept and indeed the belief he had that the Eucharist was indeed His flesh and blood.
Why don't you ever discuss those paragraphs, GPH, instead of accusing people of illiteracy? Here, I'll get you started:
20. “This is the bread that cometh down from heaven;” that by eating it we may live, since we cannot have eternal life from ourselves. Not,” saith He, “as your fathers did eat manna, and are dead: he that eateth this bread shall live forever.” That those fathers are dead, He would have to be understood as meaning, that they do not live forever. For even they who eat Christ shall certainly die temporally; but they live forever, because Christ is eternal life.
Talk about these (and the other paragraphs starting from 15) in Tractate 26. For once.
Tractate 26.