thanks,
that is my fault.
it should be
while((n = read(fd,buf0,sizeof(buf0)-1)) > 0){
and
while((n = read(pfd[0],buf,sizeof(buf)-1)) > 0){
> 2017/04/02 16:34、Skip Tavakkolian <[email protected]> のメール：
>
> this is either a bug in devpipe or the documentation is misleading. the man
> page seems to say that the pair of fd's returned by pipe(2) are symmetrical,
> but it matters which fd of the pair is used for writing. if you switch
> around pfd[0] and pfd[1], it works as you'd expect.
>
> On Fri, Mar 31, 2017 at 5:29 PM arisawa <[email protected]> wrote:
> Hello,
>
> I was playing with an experimental code on pipe and met with a problem which
> I don’t understand.
>
> the program reads a file and writes it to one end of pipe and then reads it
> from another end of pipe.
> the buffer for writing pipe is named buf0, and for reading pipe is named buf.
> and I found the program does not finish unless sizeof(buf) > sizeof(buf0).
> is this a bug or feature of pipe?
>
> Kenji Arisawa
>
> === BEGIN a.c ===
> #include <u.h>
> #include <libc.h>
>
> char *argv0;
>
> void
> usage(void)
> {
> fprint(2,"usage: %s file\n",argv0);
> exits("usage");
> }
>
> void
> main(int argc, char *argv[])
> {
> int fd,pfd[2];
> char buf[256];
> char buf0[256];
> /* need to be sizeof(buf) > sizeof(buf0)
> * but this condition is very curious to me */
> int n;
> char *file;
> argv0 = argv[0];
> argc--;argv++;
> USED(argc);
> if(argv[0] == nil)
> usage();
> file = argv[0];
> fd = open(file,OREAD);
> if(fd < 0)
> sysfatal("no such file");
>
> if(pipe(pfd) < 0)
> sysfatal("pipe error");
> print("pfd: %d %d\n",pfd[0],pfd[1]);
>
> while((n = read(fd,buf0,sizeof(buf0))) > 0){
> print("read: %d %s\n",n,file);
> n = write(pfd[1],buf0,n);
> print("write: %d\n",n);
> }
> close(pfd[1]);
> while((n = read(pfd[0],buf,sizeof(buf))) > 0){
> buf[n] = 0;
> print("%d %s\n",n,buf);
> }
> print("%d\n",n);
>
> exits(nil);
> }
> === END a.c ===
