Buffering problems

ruby-talk
1

I'm trying to redirect stdout and stderr of a program to a log file.

So, I'm doing something like:

$stdout.sync = true
$stderr.sync = true
$stdout.reopen File.open(some_log_file, "w")
$stderr.reopen File.open(some_log_file, "w")

exec 'program'

Standard out and error are being redirected to the log file, but they
are being buffered.

Any ideas on why that might be?

Thanks,
Joe

2

Just found IO::fsync...
--------------------------------------------------------------- IO#fsync
     ios.fsync => 0 or nil

···

On 10/13/05, Joe Van Dyk <joevandyk@gmail.com> wrote:

I'm trying to redirect stdout and stderr of a program to a log file.

So, I'm doing something like:

$stdout.sync = true
$stderr.sync = true
$stdout.reopen File.open(some_log_file, "w")
$stderr.reopen File.open(some_log_file, "w")

exec 'program'

Standard out and error are being redirected to the log file, but they
are being buffered.

Any ideas on why that might be?

------------------------------------------------------------------------
     Immediately writes all buffered data in _ios_ to disk. Returns
     +nil+ if the underlying operating system does not support
     _fsync(2)_. Note that +fsync+ differs from using +IO#sync=+. The
     latter ensures that data is flushed from Ruby's buffers, but
     doesn't not guarantee that the underlying operating system actually
     writes it to disk.

I'm running on Linux. Is there any way to force the OS to write data
from Ruby's buffers to the disk all that time?

3

did you mean

   $stdout.reopen File.open(some_log_file, "w")
   $stderr.reopen File.open(some_log_file, "w")
   $stdout.sync = true
   $stderr.sync = true

?

-a

···

On Fri, 14 Oct 2005, Joe Van Dyk wrote:

I'm trying to redirect stdout and stderr of a program to a log file.

So, I'm doing something like:

$stdout.sync = true
$stderr.sync = true
$stdout.reopen File.open(some_log_file, "w")
$stderr.reopen File.open(some_log_file, "w")

exec 'program'

Standard out and error are being redirected to the log file, but they
are being buffered.

Any ideas on why that might be?

--

email :: ara [dot] t [dot] howard [at] noaa [dot] gov
phone :: 303.497.6469
Your life dwells amoung the causes of death
Like a lamp standing in a strong breeze. --Nagarjuna

===============================================================================

4

Hi,

At Fri, 14 Oct 2005 06:40:05 +0900,
Joe Van Dyk wrote in [ruby-talk:160499]:

$stdout.sync = true
$stderr.sync = true
$stdout.reopen File.open(some_log_file, "w")
$stderr.reopen File.open(some_log_file, "w")

exec 'program'

IO#sync flag is only for current process.

Standard out and error are being redirected to the log file, but they
are being buffered.

Any ideas on why that might be?

One way is to let the 'program' not to buffer its output.
Another way is to use pty.

···

--
Nobu Nakada

5

No. Why would the ordering make a difference?

···

On 10/13/05, Ara.T.Howard <Ara.T.Howard@noaa.gov> wrote:

On Fri, 14 Oct 2005, Joe Van Dyk wrote:

> I'm trying to redirect stdout and stderr of a program to a log file.
>
> So, I'm doing something like:
>
> $stdout.sync = true
> $stderr.sync = true
> $stdout.reopen File.open(some_log_file, "w")
> $stderr.reopen File.open(some_log_file, "w")
>
> exec 'program'
>
> Standard out and error are being redirected to the log file, but they
> are being buffered.
>
> Any ideas on why that might be?

did you mean

   $stdout.reopen File.open(some_log_file, "w")
   $stderr.reopen File.open(some_log_file, "w")
   $stdout.sync = true
   $stderr.sync = true

6

And switching putting the sync calls after the reopen didn't seem to
make a difference.

···

On 10/13/05, Joe Van Dyk <joevandyk@gmail.com> wrote:

On 10/13/05, Ara.T.Howard <Ara.T.Howard@noaa.gov> wrote:
> On Fri, 14 Oct 2005, Joe Van Dyk wrote:
>
> > I'm trying to redirect stdout and stderr of a program to a log file.
> >
> > So, I'm doing something like:
> >
> > $stdout.sync = true
> > $stderr.sync = true
> > $stdout.reopen File.open(some_log_file, "w")
> > $stderr.reopen File.open(some_log_file, "w")
> >
> > exec 'program'
> >
> > Standard out and error are being redirected to the log file, but they
> > are being buffered.
> >
> > Any ideas on why that might be?
>
> did you mean
>
> $stdout.reopen File.open(some_log_file, "w")
> $stderr.reopen File.open(some_log_file, "w")
> $stdout.sync = true
> $stderr.sync = true

No. Why would the ordering make a difference?