Re: non-block reading from pipe stdout
On Tuesday, 3 October 2017 at 12:32:43 UTC, kdevel wrote: IMHO a program should sleep (consume 0 CPU time and 0 energy) if there is nothing to process. This is best accomplished by not polling on a file descriptor in order to check if data has arrived. If your program must yield() there's probably something wrong with the design. I would suggest you put all the filedescriptors into a fd_set an then select(3) on the set. Programs based on fibers can't sleep while wait data and it's not a design problem.
Re: non-block reading from pipe stdout
On Tuesday, 3 October 2017 at 12:20:09 UTC, Oleg B wrote:
while (!tryWait(pp.pid).terminated)
{
auto cnt = read(fd, buf.ptr, buf.length); //
C-style reading
if (cnt == -1 && errno == EAGAIN) // C-style error
checking
yield();
else if (cnt > 0)
{
doSomething(buf[0..cnt]);
yield();
}
}
IMHO a program should sleep (consume 0 CPU time and 0 energy) if
there is nothing to process. This is best accomplished by not
polling on a file descriptor in order to check if data has
arrived. If your program must yield() there's probably something
wrong with the design. I would suggest you put all the
filedescriptors into a fd_set an then select(3) on the set.
Re: non-block reading from pipe stdout
On Tuesday, 3 October 2017 at 10:45:21 UTC, kdevel wrote:
On Tuesday, 3 October 2017 at 00:22:28 UTC, Oleg B wrote:
but get error "Resource temporarily unavailable".
You get EAGAIN because there is no data available at the time
of reading.
From the manpage of read:
ERRORS
EAGAIN Non-blocking I/O has been selected using
O_NONBLOCK and no data
was immediately available for reading.
I found only one way: C-style
auto pp = pipeShell(updaterScriptCommand, Redirect.all,
null, Config.none, workDir);
import core.sys.posix.unistd : read;
import core.stdc.errno;
import core.sys.posix.fcntl;
int fd = pp.stdout.fileno;
int flags = fcntl(fd, F_GETFL, 0);
flags |= O_NONBLOCK;
fcntl(fd, F_SETFL, flags); // C-style setting file config
char[256] buf;
while (!tryWait(pp.pid).terminated)
{
auto cnt = read(fd, buf.ptr, buf.length); // C-style
reading
if (cnt == -1 && errno == EAGAIN) // C-style error
checking
yield();
else if (cnt > 0)
{
doSomething(buf[0..cnt]);
yield();
}
}
Re: non-block reading from pipe stdout
On Tuesday, 3 October 2017 at 11:36:28 UTC, Oleg B wrote: EAGAIN Non-blocking I/O has been selected using O_NONBLOCK and no data was immediately available for reading. And I can't check this without using exception handling? Your programm shall not read before data is available. Use core.sys.posix.sys.select to check if read would block on a blocking socket.
Re: non-block reading from pipe stdout
On Tuesday, 3 October 2017 at 10:45:21 UTC, kdevel wrote: On Tuesday, 3 October 2017 at 00:22:28 UTC, Oleg B wrote: but get error "Resource temporarily unavailable". You get EAGAIN because there is no data available at the time of reading. From the manpage of read: ERRORS EAGAIN Non-blocking I/O has been selected using O_NONBLOCK and no data was immediately available for reading. And I can't check this without using exception handling?
Re: non-block reading from pipe stdout
On Tuesday, 3 October 2017 at 00:22:28 UTC, Oleg B wrote: but get error "Resource temporarily unavailable". You get EAGAIN because there is no data available at the time of reading. From the manpage of read: ERRORS EAGAIN Non-blocking I/O has been selected using O_NONBLOCK and no data was immediately available for reading.
non-block reading from pipe stdout
Hello. I run program through std.process.pipeShell and want to read from it stdout in loop. How do this non-blocking? I try int fd = p.stdout.fileno; int flags = fcntl(fd, F_GETFL, 0); flags |= O_NONBLOCK; fcntl(fd, F_SETFL, flags); but get error "Resource temporarily unavailable".
