by KJK::Hyperio » Sun, 20 Apr 2003 06:06:00
by Fletcher Glen » Sun, 20 Apr 2003 06:29:04
> A terrible doubt: access to file descriptors from multiple threads is
> serialized, or each thread gets a copy of the descriptors? I'd go for
> serialization, but I'm not sure if it's the right approach
--
Fletcher Glenn
by Eric Sosma » Sun, 20 Apr 2003 06:34:43
> A terrible doubt: access to file descriptors from multiple threads is
> serialized, or each thread gets a copy of the descriptors? I'd go for
> serialization, but I'm not sure if it's the right approach
It's the kernel's job to ensure that nothing untoward
happens if T1 and T2 both call write(42,...) at "the same"
time. How the kernel handles the necessary exclusion is
up to the kernel writer.
--
by KJK::Hyperio » Sun, 20 Apr 2003 07:04:52
thanks. Another sign that I should ignore the "threads are lightweightQuote:> File descriptors belong to the process as a whole, and are thus
> shared by all the process' threads.
that's all I needed to know. ThanksQuote:> It's the kernel's job to ensure that nothing untoward happens if T1
> and T2 both call write(42,...) at "the same" time. How the kernel
> handles the necessary exclusion is up to the kernel writer.
1. "Bad file descriptor" with Bash; how to designate descriptors?
I have a trivial script which tails multiple files by
spawning a 'tail' process for each file and duping the
output into one file descriptor which is then tailed:
for f in $*; do
tail -1f $f >&3 &
done
exec <&3
tail -f
This works fine under Sun ksh, but I've just tried to run
it now with Bash under Linux 2.4.16, only to have each
command using file descriptor 3 fail with a
'Bad file descriptor'
error.
This has caught me completely unawares. The bash manpage
says that
"If the digits in word do not specify a file descriptor open
for output, a redirection error occurs"
How do I open file descriptor 3 for output? Or, if I do
something like
tail -1f file > /dev/null &
how can I find out what file descriptor is opened so I can
direct the output of further tail commands to the same
descriptor? What's the magic that bash needs to be able to
do something like this?
Many thanks,
Brad
2. dnotify fix for readv/writev (Linux 2.4.20)
5. portable way to convert FILE ptr to file descriptor?
7. how to get file length from file descriptor
8. RealAudio Player with SB 2.0 (/dev/mixer?)
9. *FILE and int as file descriptors.
10. Grabbing file from file descriptors
11. FILE descriptor and file id conversion?
12. difference b/w file pointer and file descriptor
13. kernel: Cannot read proc file system: 9 - Bad file descriptor