Date: Thu, 8 Jun 2023 21:21:53 -0400 From: Aryeh Friedman <aryeh.friedman@gmail.com> To: "Dr. Nikolaus Klepp" <dr.klepp@gmx.at> Cc: questions@freebsd.org Subject: Re: Slightly OT: non-buffered stdin in Java Message-ID: <CAGBxaXnVM=P%2B2r4o0UuEnOzhE6S9TTWbXyWFk2XGYqCsCdG44A@mail.gmail.com> In-Reply-To: <202306090036.42118.dr.klepp@gmx.at> 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>
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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 from > > > > files/sockets and other generic InputStreams unbuffered. So I was > > > > wondering if there is a command that will make stdin go to a file s= o > > > > 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" disable= s linebuffer on input by itself, so you should use someting else for testin= g. > > 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 % --=20 Aryeh M. Friedman, Lead Developer, http://www.PetiteCloud.org
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