Making Cat Command from Scratch with Assembly

[@edgeeffect]

It's nice to see somebody covering Assembly Language on KZbin with examples that actually DO SOMETHING... I'd rather you were doing MIPS and din't have an operating system, but I can't have EVERYTHING. ;)

[@YilmazDurmaz]

a practical demo to show how to use what you only read from books. nice!

[@jasdfff770]

Good video! One suggestion: a video comparing the assembly generated by a program made in C with the same program if you were to write it directly in assembly.

[@thesushifiend]

Very clever. I didn’t understand much but now I’d like to see an implementation of “dog”.

[@ZecaSamicas]

Even that assembly is getting more and more obsolete these days because of the learning curve. We can't ignore the fact that it has been not forgotten after all these decades, even with the new technology, in some rare cases, assembly is still the best choice (or C).

[@noelgallagher3646]

Assembly is not difficult just tedious. What I like is it does not give you a helping hand. Even c with a modern compiler helps you too much with optimisations. In this regard, you end up writing suboptimal code without realising since the compiler helped you

[@ZecaSamicas]

@@noelgallagher3646 Indeed Assembly can consume a lot of time, But after all, It'll probably be worth it

[@noelgallagher3646]

@@ZecaSamicas if your goal is to be a better programmer and understand what is happening on a low level then yes absolutely

[@edgeeffect]

ALL software is Open Source... IF you can read Assembly Language!

[@anukranan]

@@edgeeffect Read the hex, translate them opcodes

[@cangozpinar]

How can one fine the information used in this video such ad thr +16 bytes for the first arg ?

[@billybobjankens12]

The way someone can find this information is by searching through books, documents, and other things

[@smartnima]

Keep making this amazing content!

[@iAmVonexX]

i barely understood half of it but damn you know how to make videos simple but interesting

[@nirlichtman]

Thanks! What specifically did you not understand? I can help explain

[@iAmVonexX]

i might have exaggerated what i understood. i'm not a dev by any means so you would have to explain basically everything to me. and that might go beyond the scope of a youtube comment ^^

[@nirlichtman]

@@iAmVonexX 👍 if you want a more beginner friendly video that could help understand this a little better I would recommend my video explaining linux system calls

[@jasdfff770]

It would be nice a video explaining the function of each register. Nice work, by the way!!

[@JoaoCarlos-df1zw]

The real definition of blazing fast

[@darshangaikwad1392]

this is good make more stuff like this

[@ayoubelmhamdi7920]

viewing the registers names, doesn't mean we remember all of them, i think the better way, is to keep a small table on the right side, so we not be lose the context

[@nirlichtman]

That's a good idea, thanks for the feedback 👍

[@MarkVeltzer]

This is weird, I keep getting EINVAL on the call to sendfile.... I tried a version of C of this with simply open(2) and sendfile(2) and got -EINVAL too...

[@nirlichtman]

What kernel version and architecture are you using?

[@ibragimyouldachevcn3415]

@nirlichtman It appears that the occurrence of EINVAL is attributed to the fact that 'stdout' has the O_APPEND flag. Specifically, the error is described as follows: "EINVAL out_fd has the O_APPEND flag set. This is not currently supported by sendfile()."

[@AMith-lv2cv]

more of this masterpiece

[@tankman1301]

awesome!

[@codedsprit]

Here we gooo

[@Haydenz11]

A+

[@patriciaverso]

I can't seem to make this work. I don't know if the Kernel version has anything to do with it. I'm getting this as my strace. Do you think you could take a look? execve("./a.out", ["./a.out", "cat.asm"], 0x7ffdd1a38548 /* 85 vars */) = 0 open("cat.asm", O_RDONLY) = 3 sendfile(1, 3, NULL, 100) = -1 EINVAL (Invalid argument) ^C--- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} --- I also tried the sendfile syscall in C to check if that was faulty for some reason, but that worked.

[@nirlichtman]

Interesting and did you run the strace on the C code as well to see how sendfile was called? Also what is your setup - distro version and arch?