# How do I read a binary file back into an Array?

**URL:** https://discourse.julialang.org/t/how-do-i-read-a-binary-file-back-into-an-array/28454
**Category:** New to Julia
**Tags:** binaryio
**Created:** [September 6, 2019, 2:30am UTC](https://discourse.julialang.org/t/how-do-i-read-a-binary-file-back-into-an-array/28454 "2019-09-06T02:30:09Z")
**Posts on this page:** 2
**Page:** 1

<div class="post-metadata">

### Author: ![xiaodai](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/xiaodai/32/15937_2.png) [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [September 6, 2019, 2:30am UTC](https://discourse.julialang.org/t/how-do-i-read-a-binary-file-back-into-an-array/28454/1 "2019-09-06T02:30:09Z")

</div>

I have written an `Vector{UInt}` into a binary file and I want to read the binary file back into a `Vector{UInt}`. How do I do that?

```julia
# write it out
bbc = rand(UInt8, 100)
io = open("io.test", "w")
write(io, bbc)
close(io)

# read back in
io = open("io.test", "r")
bbc_new = read(io, Vector{UInt})
close(io)

```

I get error

```julia
ERROR: The IO stream does not support reading objects of type Array{UInt64,1}.

```

---

<div class="post-metadata">

### Author: ![xiaodai](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/xiaodai/32/15937_2.png) [@xiaodai](https://discourse.julialang.org/u/xiaodai)
#### Post date: [September 6, 2019, 2:35am UTC](https://discourse.julialang.org/t/how-do-i-read-a-binary-file-back-into-an-array/28454/2 "2019-09-06T02:35:29Z")

</div>

Found a solution here.

```julia
bbc_new = Array{UInt8,1}(undef, 100)

read!(io, bbc_new)

close(io)

```