09-02-2009
Redirecting stdin from fd 3-9?
Hi
I'm trying to do something on the bash command line that I will later put into a bash shell script.
I'm trying to take a program that reads stdin (using getline) and be able to keep it running in the background and fire "commands" to it. So what I thought I should do was to try taking stdin from (arbitrarily) file descriptor 4:
./myprogram <&4 &
Then later:
echo "inputstring" >&4
then later again
cat somefile >&4
This results is bash telling me "Bad file descriptor" when I start ./myprogram
The whole point of this is to exercise a library that I've written. Its wrapped in a C frontend that takes input from stdin (like a psuedo command line program). It's got to stay alive though so the data in my library under test can stay persistent.
Any idea if this is possible?
Last edited by niceguyeddie; 09-02-2009 at 05:00 PM..
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LEARN ABOUT CENTOS
hwloc-ps
HWLOC-PS(1) hwloc HWLOC-PS(1)
NAME
hwloc-ps - List currently-running processes or threads that are bound
SYNOPSIS
hwloc-ps [options]
OPTIONS
-a list all processes, even those that are not bound to any specific part of the machine.
-p --physical
report OS/physical indexes instead of logical indexes
-l --logical
report logical indexes instead of physical/OS indexes (default)
-c --cpuset
show process bindings as cpusets instead of objects.
-t --threads
show threads inside processes. If -a is given as well, list all threads within each process. Otherwise, show all threads inside
each process where at least one thread is bound.
--whole-system
Do not consider administration limitations.
--pid-cmd <cmd>
Append the output of the given command to each PID line. For each displayed process ID, execute the command <cmd> <pid> and
append the first line of its output to the regular hwloc-ps line.
DESCRIPTION
By default, hwloc-ps lists only those currently-running processes that are bound. If -t is given, processes that are not bound but contain
at least one bound thread are also displayed, as well as all their threads.
hwloc-ps displays process identifier, command-line and binding. The binding may be reported as objects or cpusets.
By default, process bindings are restricted to the currently available topology. If some processes are bound to processors that are not
available to the current process, they are ignored unless --whole-system is given.
The output is a plain list. If you wish to annotate the hierarchical topology with processes so as to see how they are actual distributed
on the machine, you might want to use lstopo --ps instead (which also only shows processes that are bound).
The -a switch can be used to show all processes, if desired.
EXAMPLES
If a process is bound, it appears in the default output:
$ utils/hwloc-ps
4759 Core:0 myprogram
If a process is not bound but 3 of his 4 threads are bound, it only appears in the thread-aware output:
$ utils/hwloc-ps
$ utils/hwloc-ps -t
4759 Machine:0 myprogram
4759 Machine:0
4761 PU:0
4762 PU:2
4765 PU:1
To display the binding of already running MPI processes (launched by Open MPI) and append their MPI rank (in MPI_COMM_WORLD) to each line:
$ utils/hwloc-ps --pid-cmd myscript
29093 L1dCache:0 myprogram OMPI_COMM_WORLD_RANK=0
29094 L1dCache:2 myprogram OMPI_COMM_WORLD_RANK=1
29095 L1dCache:1 myprogram OMPI_COMM_WORLD_RANK=2
29096 L1dCache:3 myprogram OMPI_COMM_WORLD_RANK=3
where myscript is a bash script doing:
#!/bin/sh
cat /proc/$1/environ 2>/dev/null | xargs --null --max-args=1 echo | grep OMPI_COMM_WORLD_RANK
SEE ALSO
hwloc(7), lstopo(1), hwloc-calc(1), hwloc-distrib(1)
1.7 Apr 07, 2013 HWLOC-PS(1)