hello, It seems like your OS (Linux here) is buffering all successive open-write-close sequences together and lumping all data together that can be read with a single open-read-close sequence. Here is a trace of the system calls for both the writer (first) and the reader (second).

# this is the writer trace
# this sequence is repeated 4 times
open("tst.fifo", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3
fstat64(3, {st_mode=S_IFIFO|0644, st_size=0, ...}) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
fstat64(3, {st_mode=S_IFIFO|0644, st_size=0, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 
+-1, 0) = 0x40016000
write(3, "This is some silly,\n", 20)   = 20
close(3)                                = 0
munmap(0x40016000, 4096)                = 0
[download]

# this is the reader trace
# notice how we got all 82 bytes at one shot
write(1, "Opening pipe: ", 14)          = 14
open("tst.fifo", O_RDONLY|O_LARGEFILE)  = 3
fstat64(3, {st_mode=S_IFIFO|0644, st_size=0, ...}) = 0
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
write(1, "got pipe, reading:\n", 19)    = 19
fstat64(3, {st_mode=S_IFIFO|0644, st_size=0, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 
+-1, 0) = 0x40017000
read(3, "This is some silly,\nstuff to be "..., 4096) = 82
read(3, "", 4096)                       = 0
write(1, ": This is some silly,\n", 22) = 22
write(1, ": stuff to be sent\n", 19)    = 19
write(1, ": to the pipe where hopefully\n", 30) = 30
write(1, ": it will be read.\n", 19)    = 19
write(1, "Pipe done, closing: ", 20)    = 20
close(3)                                = 0
munmap(0x40017000, 4096)                = 0
write(1, "done.\n", 6)                  = 6
write(1, "Taking a long time... ", 22)  = 22
time([1009160476])                      = 1009160476
[download]

So, is this a bug? Dunno, since I'm not familiar with the POSIX specs on pipes.

Hope this helps.

Aziz,,,

Update:

From the pipe(4) man page:

       Under  Linux,  opening a FIFO for read and write will suc?
       ceed both in blocking and non-blocking mode. POSIX  leaves
       this  behaviour undefined. This can be used to open a FIFO
       for writing while there are no readers available.  A  pro?
       cess  that  uses  both  ends of the connection in order to
       communicate with itself should be very  careful  to  avoid
       deadlocks.
[download]

So, I guess under linux, the kernel choses to buffer the input when there are multiple succesive writes to a named pipe.

Hope this helps...

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