# Read hourly I/O API data with I/O API

**URL:** <https://forum.cmascenter.org/t/read-hourly-i-o-api-data-with-i-o-api/1752>\
**Category:** I/O API\
**Created:** [September 4, 2020, 7:19am UTC](https://forum.cmascenter.org/t/read-hourly-i-o-api-data-with-i-o-api/1752 "2020-09-04T07:19:17Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![franky](https://avatars.discourse-cdn.com/v4/letter/f/958977/32.png) [@franky](https://forum.cmascenter.org/u/franky)\
**Post date:** [September 4, 2020, 7:19am UTC](https://forum.cmascenter.org/t/read-hourly-i-o-api-data-with-i-o-api/1752/1 "2020-09-04T07:19:17Z")

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Could anyone know how to use I/O API to read more than 2 files.  
I have successfuly use I/O API function OPEN3/READ3/WRITE3 to operate one file with environment variable. But i don’t know how to read or write more than 1 file.  
Many thanks. Looke forward to your reply.

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**Author:** ![cjcoats](https://avatars.discourse-cdn.com/v4/letter/c/ac8455/32.png) [@cjcoats](https://forum.cmascenter.org/u/cjcoats)\
**Post date:** [September 4, 2020, 3:43pm UTC](https://forum.cmascenter.org/t/read-hourly-i-o-api-data-with-i-o-api/1752/2 "2020-09-04T15:43:59Z")

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If you’ve installed the I/O API, you should have both the _ioapi-3.2/ioapi_ and the _ioapi-3.2/m3tools_ source directories. In the latter are many multi-file programs (most of them are at least two-file), perhaps the most extreme of which is _m3combo.f90_ which potentially deals with hundreds of input-files and one output-file. _vertintegral.f90_ is perhaps a more-conventional example: it reads a `CONC` file and a `METCRO3D` file, and creates a file with 2-D vertically-integrated species-values (it’s also a demonstration of how to do effective OpenMP parallelism…)

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**Author:** ![franky](https://avatars.discourse-cdn.com/v4/letter/f/958977/32.png) [@franky](https://forum.cmascenter.org/u/franky)\
**Post date:** [September 7, 2020, 5:20am UTC](https://forum.cmascenter.org/t/read-hourly-i-o-api-data-with-i-o-api/1752/3 "2020-09-07T05:20:44Z")

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Thanks. m3combo.f90 is an excellencent examble for reading multi-file wiht “STRLIST”.  
Another question, can i read read unformaated m3 netcdf file with I/O API, like netcdf file without headers?

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**Author:** ![cjcoats](https://avatars.discourse-cdn.com/v4/letter/c/ac8455/32.png) [@cjcoats](https://forum.cmascenter.org/u/cjcoats)\
**Post date:** [September 7, 2020, 3:26pm UTC](https://forum.cmascenter.org/t/read-hourly-i-o-api-data-with-i-o-api/1752/4 "2020-09-07T15:26:41Z")

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No, there are internal data structures in the file-headers that are required in I/O API files, that are used for a variety of purposes including data-integrity assurance.

However. I/O API module `MODNCFIO` (see [https://cjcoats.github.io/ioapi/MODNCFIO.html](https://cjcoats.github.io/ioapi/MODNCFIO.html)) provides a number of routines providing high-level/modeler-friendly access to “raw” netCDF, and module `MODWRFIO` (see [https://cjcoats.github.io/ioapi/MODWRFIO.html](https://cjcoats.github.io/ioapi/MODWRFIO.html)) provides high-level access to WRF-format netCDF.