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Hi Dennis,
Thank you for the suggestion. I already have a wrapper around the create/open
calls that pass a unique I/O structure for each file type. My system
manipulates lots of different NetCDF files that I need to track. It is
complicated with parallel I/O that may use or not disjointed and dedicated I/O
processes.
Cheers, H
On 1/22/21, 11:25 PM, "Dennis Heimbigner" <dmh@xxxxxxxx> wrote:
It is doable, I think. Basically you need to walk the internal list of
open files
looking for a name match. This is probably complicated if mpio is being used
because that list is duplicated on every processor.
As an alternative, you could implement wrapper around nc_create and nc_open
that call the regular nc_create/nc_open, but also keep a list of the
names of the
path arguments.
=Dennis Heimbigner
Unidata
On 1/22/2021 8:35 PM, Hernan Arango wrote:
>
> Hi Lucas,
>
> Thank you for your answer. However, what I am specifically asking is:
> Given ONLY the NetCDF dataset filename, is there a function that can
> be used in a Fortran code (or a C-binding routine) to inquire if the
> filename is open (with a logical true or false result). If true,
> return the one or more identifiers (vector) associated with the
> opening of that specific filename. Notice that It is possible that
> such filename has been opened more than once and not closed.
>
> I assume that this is a very difficult question because I don’t have
> an idea how to code such function. Maybe the developers of NetCDF can
> tell us if it is possible or not.
>
> Cheers, Hernan
>
> *From: *Lucas Villa Real <lucasvr@xxxxxxxxxx>
> *Date: *Friday, January 22, 2021 at 10:17 PM
> *To: *Hernan Arango <arango@xxxxxxxxxxxxxxxxxx>
> *Cc: *"netcdfgroup@xxxxxxxxxxxxxxxx" <netcdfgroup@xxxxxxxxxxxxxxxx>
> *Subject: *Re: [netcdfgroup] How to inquire if a NetCDF file is
> already open for reading or writing?
>
> ----- Original message -----
> From: Hernan Arango <arango@xxxxxxxxxxxxxxxxxx>
> Sent by: "netcdfgroup" <netcdfgroup-bounces@xxxxxxxxxxxxxxxx>
> To: "netcdfgroup@xxxxxxxxxxxxxxxx" <netcdfgroup@xxxxxxxxxxxxxxxx>
> Cc:
> Subject: [EXTERNAL] [netcdfgroup] How to inquire if a NetCDF file
> is already open for reading or writing?
> Date: Fri, Jan 22, 2021 6:01 PM
>
>
> Hello,
>
> I am wondering if there is a function to determine if a NetCDF is
> already open for reading or writing based on the filename? I am
> trying to avoid open too many files. I know that there are ways
> in Unix to increase the number of open files, but that’s not what
> I am asking. In parallel I/O running on lots of processes, there
> is a need to avoid opening too many files. I am using both the
> standard NetCDF library and the PIO library that is the basis of
> the SCORPIO library (https://e3sm.org/scorpio-parallel-io-library
>
<https://urldefense.proofpoint.com/v2/url?u=https-3A__e3sm.org_scorpio-2Dparallel-2Dio-2Dlibrary&d=DwMGaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=yZCLoPFNF2xM1OIVBISlXxZvERMVKNT1d5PSrOJfnc8&m=QnVlDcV5suiBIhpLT3T5oRt9rSpedaNzD5PPQIaVwoY&s=9fcAm4IjIU6e3FbfD7JzZm28BtCM1zMwV3G7jQ-Bc0A&e=>).
> Therefore, I have integer file ID (ncid) and file descriptors of
> TYPE (file_desc_t).
>
> I am looking for something like:
>
> ncid=is_nc_open(‘my_file.nc’)
>
> or
>
> fileDesc=is_pio_open(iosystem, my_paralle_file.nc’)
>
> Thank you, H
>
> Hi Hernan,
>
> If you're on Linux, then one option is to scan the symlinks under
> /proc/self/fd looking for a target whose name matches the file name
> you're looking for.
>
> I'm not sure if ncids have a 1:1 correspondence with HDF5 file ids; if
> they do, then perhaps you could also look into H5Fget_obj_count(ncid,
> H5F_OBJ_FILE) and/or H5Fget_obj_count(H5F_OBJ_ALL, H5F_OBJ_FILE). See
> https://support.hdfgroup.org/HDF5/doc/RM/RM_H5F.html#File-GetObjCount
> <https://support.hdfgroup.org/HDF5/doc/RM/RM_H5F.html#File-GetObjCount>
> for more details on that API.
>
> Best regards,
>
> Lucas
>
>
>
>
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