# Hdf5read inputs

**URL:** <https://discourse.julialang.org/t/hdf5read-inputs/11513>\
**Category:** General Usage\
**Tags:** hdf5\
**Created:** [June 7, 2018, 4:24pm UTC](https://discourse.julialang.org/t/hdf5read-inputs/11513 "2018-06-07T16:24:36Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![VDC](https://avatars.discourse-cdn.com/v4/letter/v/7ba0ec/32.png) [@VDC](https://discourse.julialang.org/u/VDC)\
**Post date:** [June 7, 2018, 4:24pm UTC](https://discourse.julialang.org/t/hdf5read-inputs/11513/1 "2018-06-07T16:24:36Z")

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Hello, everyone!

Have a question regarding hdf5 package in Julia, specifically the hdf5read function?

I see this in the main page of the github

A = collect(reshape(1:120, 15, 8))  
h5write(“/tmp/test2.h5”, “mygroup2/A”, A)  
data = h5read(“/tmp/test2.h5”, “mygroup2/A”, (2:3:15, 3:5))

I understand the data is stored in A, and that we are writing the data stored in A to the file called, “/tmp/test2.h5”, but what is the “mygroup2/A” pointing to? It is also there in the h5read function. Is it some kind of field that is already present in the data? Am used to using Matlab and when I use read functions, i generally just give the filename as input, so I am confused as to what the “mygroup2/A” input is doing exactly and what it is.

Thanks!  
Ginny

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**Author:** ![mbauman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mbauman/32/31082_2.png) [@mbauman](https://discourse.julialang.org/u/mbauman)\
**Post date:** [June 7, 2018, 9:52pm UTC](https://discourse.julialang.org/t/hdf5read-inputs/11513/2 "2018-06-07T21:52:49Z")

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HD5 files are themselves kinda like a mini-filesystem. Not only can you give your data a name, you can also organize it into “groups” — kinda like directories within the file itself. In this case, you’re storing the data with the name `"A"` within a group `"mygroup2"`. You don’t need to use groups, but HDF5.jl supports them.

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**Author:** ![VDC](https://avatars.discourse-cdn.com/v4/letter/v/7ba0ec/32.png) [@VDC](https://discourse.julialang.org/u/VDC)\
**Post date:** [June 8, 2018, 5:24pm UTC](https://discourse.julialang.org/t/hdf5read-inputs/11513/3 "2018-06-08T17:24:49Z")

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Thanks, Matt!  
That makes a lot of sense now 🙂