On Thu, 21 Jun 2018 00:56:04 +0200
Tomasz Rola <rto...@ceti.pl> wrote:
> On Thu, Jun 21, 2018 at 12:44:14AM +0200, Tomasz Rola wrote:
> [...]
> > => (591 60): cat nread
> > #!/bin/sh
> >
> > # nread n - read up to n bytes from stdio, put them on to stdout
> >
> > N=$1
> >
> > dd bs=512 count=$((N / 512)) iflag=fullblock 2>/dev/null
> > dd bs=1 count=$((N % 512)) iflag=fullblock 2>/dev/null
>
> Craps. I have consulted OpenBSD's manpage for dd and there is no
> mention of iflag. So this will not work on OpenBSD. I will have to
> rethink this, sorry.
>
Untested...
int main(int argc, char* argv[]){
long l = atod(argv[1]);
while(l--){
if (c = getc(STDIN) != EOF)
putc(c, STDOUT);
else
break;
}
return 0;
}
I haven't tested it so it might not be exactly right, and of course
error handling would need to be added, but you know what I mean. IIRC
getc() and putc() are very well buffered so it will be fast. In my
youth I wrote similar functions using low level read() and write() and
doing my own buffering, and those things were *really* fast, but I
think that's overkill in this century.
As far as finding command line tools that do it, if that's becoming
hard to do, why not just write a 10 line program?
--
SteveT
Steve Litt
June 2018 featured book: Twenty Eight Tales of Troubleshooting
http://www.troubleshooters.com/28
