Date: Thu, 8 Jun 2023 23:37:39 -0400 From: Paul Procacci <pprocacci@gmail.com> To: Aryeh Friedman <aryeh.friedman@gmail.com> Cc: "Dr. Nikolaus Klepp" <dr.klepp@gmx.at>, questions@freebsd.org, freebsd-java@freebsd.org Subject: Re: Slightly OT: non-buffered stdin in Java Message-ID: <CAFbbPuh7NuHgTTm6iQ%2BsGWPpct7dYMBZDw80CbZrt7T_SRGSmQ@mail.gmail.com> In-Reply-To: <CAGBxaXkF2AwM8oXwDwWWkiaBO_Kpe-QAxXi9HekEuQLkqY3Bwg@mail.gmail.com> References: <CAGBxaX=muu6JbMsdZbop7mYa-LetXPHvO8_=kMZtF%2BzSAdiBYA@mail.gmail.com> <202306082039.36831.dr.klepp@gmx.at> <CAGBxaXnq%2BU9C7=Vepc4Poq8LaZCo8DnkPpMH5UT70dUsKrG3bw@mail.gmail.com> <202306090036.42118.dr.klepp@gmx.at> <CAGBxaXnVM=P%2B2r4o0UuEnOzhE6S9TTWbXyWFk2XGYqCsCdG44A@mail.gmail.com> <CAFbbPuhvy=rtBU0iSJzyrxWdPYamXeFcGdBkUPYEvkLt46UyBA@mail.gmail.com> <CAGBxaXm6hP9YUCtbV2Cumvn=LWy7TgYctLA-tZU=GSrP8hg9Jw@mail.gmail.com> <CAFbbPugCnZWvPXCmicmNP_Z0e3xhxqESNSFeSLM-HAxBn913Kw@mail.gmail.com> <CAGBxaXkF2AwM8oXwDwWWkiaBO_Kpe-QAxXi9HekEuQLkqY3Bwg@mail.gmail.com>
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--000000000000f1007605fdaa17df Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, Jun 8, 2023 at 11:36=E2=80=AFPM Aryeh Friedman <aryeh.friedman@gmai= l.com> wrote: > On Thu, Jun 8, 2023 at 11:23=E2=80=AFPM Paul Procacci <pprocacci@gmail.co= m> wrote: > > > > > > > > On Thu, Jun 8, 2023 at 10:55=E2=80=AFPM Aryeh Friedman <aryeh.friedman@= gmail.com> > wrote: > >> > >> On Thu, Jun 8, 2023 at 10:32=E2=80=AFPM Paul Procacci <pprocacci@gmail= .com> > wrote: > >> > > >> > > >> > > >> > On Thu, Jun 8, 2023 at 9:22=E2=80=AFPM Aryeh Friedman < > aryeh.friedman@gmail.com> wrote: > >> >> > >> >> On Thu, Jun 8, 2023 at 6:37=E2=80=AFPM Dr. Nikolaus Klepp <dr.klepp= @gmx.at> > wrote: > >> >> > > >> >> > Anno domini 2023 Thu, 8 Jun 17:22:38 -0400 > >> >> > Aryeh Friedman scripsit: > >> >> > > On Thu, Jun 8, 2023 at 2:39=E2=80=AFPM Dr. Nikolaus Klepp < > dr.klepp@gmx.at> wrote: > >> >> > > > > >> >> > > > Anno domini 2023 Thu, 8 Jun 14:01:19 -0400 > >> >> > > > Aryeh Friedman scripsit: > >> >> > > > > Under Java stdin (System.in) is a buffered stream not sent > to the > >> >> > > > > application until return is pressed. But, Java can read fr= om > >> >> > > > > files/sockets and other generic InputStreams unbuffered. > So I was > >> >> > > > > wondering if there is a command that will make stdin go to = a > file so > >> >> > > > > that Java can open that file and read it unbuffered? > >> >> > > > > > >> >> > > > > I know I can do something like cat ->file but that makes it > hard to > >> >> > > > > sync stdout and stderr (both are unbuffered in Java) with > the file > >> >> > > > > version of stdin > >> >> > > > > > >> >> > > > > >> >> > > > "stdbuf" might be what you look for: > >> >> > > > > >> >> > > > https://man.freebsd.org/cgi/man.cgi?query=3Dstdbuf > >> >> > > > >> >> > > Will likely need to play with it more but stdbuf -i 0 -o 0 cat > -|cat > >> >> > > didn't produce the expected immediate echo I still had to hit > return > >> >> > > > >> >> > > >> >> > Your console is linebuffered, so "cat" receives lines. IIRC "cat" > disables linebuffer on input by itself, so you should use someting else f= or > testing. > >> >> > > >> >> > Nik > >> >> > > >> >> > >> >> I am pretty convinced by the following test it is not working as > advertised: > >> >> > >> >> aryehl@neomarx:~/Desktop % cat foo.c > >> >> #include <stdio.h> > >> >> #include <fcntl.h> > >> >> #include <unistd.h> > >> >> > >> >> int main() > >> >> { > >> >> int in=3Dfcntl(STDIN_FILENO, F_DUPFD, 0); > >> >> int out=3Dfcntl(STDOUT_FILENO, F_DUPFD, 0); > >> >> char c=3D0; > >> >> > >> >> do { > >> >> read(in,&c,1); > >> >> write(out,&c,1); > >> >> } while(c!=3DEOF); > >> >> } > >> >> aryehl@neomarx:~/Desktop % !cc > >> >> cc foo.c > >> >> aryehl@neomarx:~/Desktop % stdbuf -i 0 -o 0 ./a.out > >> >> this is not echoing! > >> >> this is not echoing! > >> >> neither is this > >> >> neither is this > >> >> ^C > >> >> aryehl@neomarx:~/Desktop % > >> >> > >> >> -- > >> >> Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org > >> >> > >> > > >> > stdbuf only works for stdio buffering of which read(2) and write(2) > aren't. > >> > >> I also tried it with System.in.read() in Java and it was also buffered > >> but according to the openjdk source it appears that this is on > >> purpose. > >> > >> > >> > >> -- > >> Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org > > > > > > > > When you just `./a.out` you're being bitten by the tty. > > You can manipulate that terminal to do what you want. Start reading > termios(4). > > > > Without a tty you will only get a character at a time with the followin= g: > > > > #include <unistd.h> > > > > int main(int argc, char **argv) > > { > > char ch; > > for(;;){ > > ssize_t r =3D read(0,&ch,1); > > if(!r) break; > > write(1, &ch, 1); > > } > > _exit(0); > > } > > Please see the whole context the goal is to make it so I can type at > the command line into a java program and have instantaneous > presentation of any characters I enter to Java > > > > -- > Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org > So take what I said and apply it to java. A quick google search: https://github.com/nyholku/purejavacomm/blob/master/src/jtermios/Termios.ja= va ~Paul --=20 __________________ :(){ :|:& };: --000000000000f1007605fdaa17df Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div><div dir=3D"ltr"><br></div><br><div class=3D"gmail_qu= ote"><div dir=3D"ltr" class=3D"gmail_attr">On Thu, Jun 8, 2023 at 11:36=E2= =80=AFPM Aryeh Friedman <<a href=3D"mailto:aryeh.friedman@gmail.com">ary= eh.friedman@gmail.com</a>> wrote:<br></div><blockquote class=3D"gmail_qu= ote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,20= 4);padding-left:1ex">On Thu, Jun 8, 2023 at 11:23=E2=80=AFPM Paul Procacci = <<a href=3D"mailto:pprocacci@gmail.com" target=3D"_blank">pprocacci@gmai= l.com</a>> wrote:<br> ><br> ><br> ><br> > On Thu, Jun 8, 2023 at 10:55=E2=80=AFPM Aryeh Friedman <<a href=3D"= mailto:aryeh.friedman@gmail.com" target=3D"_blank">aryeh.friedman@gmail.com= </a>> wrote:<br> >><br> >> On Thu, Jun 8, 2023 at 10:32=E2=80=AFPM Paul Procacci <<a href= =3D"mailto:pprocacci@gmail.com" target=3D"_blank">pprocacci@gmail.com</a>&g= t; wrote:<br> >> ><br> >> ><br> >> ><br> >> > On Thu, Jun 8, 2023 at 9:22=E2=80=AFPM Aryeh Friedman <<a = href=3D"mailto:aryeh.friedman@gmail.com" target=3D"_blank">aryeh.friedman@g= mail.com</a>> wrote:<br> >> >><br> >> >> On Thu, Jun 8, 2023 at 6:37=E2=80=AFPM Dr. Nikolaus Klepp= <<a href=3D"mailto:dr.klepp@gmx.at" target=3D"_blank">dr.klepp@gmx.at</= a>> wrote:<br> >> >> ><br> >> >> > Anno domini 2023 Thu, 8 Jun 17:22:38 -0400<br> >> >> >=C2=A0 Aryeh Friedman scripsit:<br> >> >> > > On Thu, Jun 8, 2023 at 2:39=E2=80=AFPM Dr. Niko= laus Klepp <<a href=3D"mailto:dr.klepp@gmx.at" target=3D"_blank">dr.klep= p@gmx.at</a>> wrote:<br> >> >> > > ><br> >> >> > > > Anno domini 2023 Thu, 8 Jun 14:01:19 -0400= <br> >> >> > > >=C2=A0 Aryeh Friedman scripsit:<br> >> >> > > > > Under Java stdin (System.in) is a buf= fered stream not sent to the<br> >> >> > > > > application until return is pressed.= =C2=A0 But, Java can read from<br> >> >> > > > > files/sockets and other generic Input= Streams unbuffered.=C2=A0 =C2=A0So I was<br> >> >> > > > > wondering if there is a command that = will make stdin go to a file so<br> >> >> > > > > that Java can open that file and read= it unbuffered?<br> >> >> > > > ><br> >> >> > > > > I know I can do something like cat -&= gt;file but that makes it hard to<br> >> >> > > > > sync stdout and stderr (both are unbu= ffered in Java) with the file<br> >> >> > > > > version of stdin<br> >> >> > > > ><br> >> >> > > ><br> >> >> > > > "stdbuf" might be what you look = for:<br> >> >> > > ><br> >> >> > > > <a href=3D"https://man.freebsd.org/cgi/man= .cgi?query=3Dstdbuf" rel=3D"noreferrer" target=3D"_blank">https://man.freeb= sd.org/cgi/man.cgi?query=3Dstdbuf</a><br> >> >> > ><br> >> >> > > Will likely need to play with it more but stdbu= f -i 0 -o 0 cat -|cat<br> >> >> > > didn't produce the expected immediate echo = I still had to hit return<br> >> >> > ><br> >> >> ><br> >> >> > Your console is linebuffered, so "cat" rec= eives lines. IIRC "cat" disables linebuffer on input by itself, s= o you should use someting else for testing.<br> >> >> ><br> >> >> > Nik<br> >> >> ><br> >> >><br> >> >> I am pretty convinced by the following test it is not wor= king as advertised:<br> >> >><br> >> >> aryehl@neomarx:~/Desktop % cat foo.c<br> >> >> #include <stdio.h><br> >> >> #include <fcntl.h><br> >> >> #include <unistd.h><br> >> >><br> >> >> int main()<br> >> >> {<br> >> >>=C2=A0 =C2=A0 =C2=A0int in=3Dfcntl(STDIN_FILENO, F_DUPFD, = 0);<br> >> >>=C2=A0 =C2=A0 =C2=A0int out=3Dfcntl(STDOUT_FILENO, F_DUPFD= , 0);<br> >> >>=C2=A0 =C2=A0 =C2=A0char c=3D0;<br> >> >><br> >> >>=C2=A0 =C2=A0 =C2=A0do {<br> >> >>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0read(in,&c,1);<br> >> >>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0write(out,&c,1);<br> >> >>=C2=A0 =C2=A0 =C2=A0} while(c!=3DEOF);<br> >> >> }<br> >> >> aryehl@neomarx:~/Desktop % !cc<br> >> >> cc foo.c<br> >> >> aryehl@neomarx:~/Desktop % stdbuf -i 0 -o 0 ./a.out<br> >> >> this is not echoing!<br> >> >> this is not echoing!<br> >> >> neither is this<br> >> >> neither is this<br> >> >> ^C<br> >> >> aryehl@neomarx:~/Desktop %<br> >> >><br> >> >> --<br> >> >> Aryeh M. Friedman, Lead Developer, <a href=3D"http://www.= PetiteCloud.org" rel=3D"noreferrer" target=3D"_blank">http://www.PetiteClou= d.org</a><br> >> >><br> >> ><br> >> > stdbuf only works for stdio buffering of which read(2) and wr= ite(2) aren't.<br> >><br> >> I also tried it with System.in.read() in Java and it was also buff= ered<br> >> but according to the openjdk source it appears that this is on<br> >> purpose.<br> >><br> >><br> >><br> >> --<br> >> Aryeh M. Friedman, Lead Developer, <a href=3D"http://www.PetiteClo= ud.org" rel=3D"noreferrer" target=3D"_blank">http://www.PetiteCloud.org</a>= <br> ><br> ><br> ><br> > When you just `./a.out` you're being bitten by the tty.<br> > You can manipulate that terminal to do what you want.=C2=A0 Start read= ing termios(4).<br> ><br> > Without a tty you will only get a character at a time with the followi= ng:<br> ><br> > #include <unistd.h><br> ><br> > int main(int argc, char **argv)<br> > {<br> >=C2=A0 =C2=A0char ch;<br> >=C2=A0 =C2=A0for(;;){<br> >=C2=A0 =C2=A0 =C2=A0ssize_t r =3D read(0,&ch,1);<br> >=C2=A0 =C2=A0 =C2=A0if(!r) break;<br> >=C2=A0 =C2=A0 =C2=A0write(1, &ch, 1);<br> >=C2=A0 =C2=A0}<br> >=C2=A0 =C2=A0_exit(0);<br> > }<br> <br> Please see the whole context the goal is to make it so I can type at<br> the command line into a java program and have instantaneous<br> presentation of any characters I enter to Java<br> <br> <br> <br> -- <br> Aryeh M. Friedman, Lead Developer, <a href=3D"http://www.PetiteCloud.org" r= el=3D"noreferrer" target=3D"_blank">http://www.PetiteCloud.org</a><br>; </blockquote></div><br clear=3D"all"><br></div><div>So take what I said and= apply it to java.</div><div><br></div><div>A quick google search:<br></div= ><div><a href=3D"https://github.com/nyholku/purejavacomm/blob/master/src/jt= ermios/Termios.java">https://github.com/nyholku/purejavacomm/blob/master/sr= c/jtermios/Termios.java</a><br></div><div><br></div><div>~Paul</div><div><b= r></div><div><span class=3D"gmail_signature_prefix">-- </span><br><div dir= =3D"ltr" class=3D"gmail_signature">__________________<br><br>:(){ :|:& = };:</div></div></div> --000000000000f1007605fdaa17df--
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