# How can I close files for writing within a loop

**URL:** <https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923>\
**Category:** General Usage\
**Tags:** question, filesystem\
**Created:** [July 7, 2022, 11:11pm UTC](https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923 "2022-07-07T23:11:54Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![thehalfspace](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/thehalfspace/32/7217_2.png) [@thehalfspace](https://discourse.julialang.org/u/thehalfspace)\
**Post date:** [July 7, 2022, 11:11pm UTC](https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923/1 "2022-07-07T23:11:54Z")

</div>

I want to store output for a simulation. I want to be able to change the number of output files the code creates based on user input.

Here is what I have so far, everything is inside main:

```julia

function main()
out_loc = [5.0, 10.0, 15.0, 20.0, 25.0] # This will change based on what the user wants

for i in out_loc
    open(string(out_path, "time_series_depth_",i, "km.out"), "w") do i
	   write(i, "t slip sliprate shear_stress state")
end # for

# Time loop of simulation
while t < tmax
    for i in 1:length(out_loc)
        write(string(out_loc[i]), join(hcat(t, slip, sliprate, shear_stress, state), " "), "\n")
    end # for

end # while

# Close the files
for i in out_loc
    end # the open statements
end # for

end # main

```

Having these `end` statements in the for loop somehow messes up and gives a variable scope error (it is possibly parsing the first `end` as `end main function`). Is there any efficient way to do this?

As always, thanks for any help 😄

EDIT: Context: I have a very large fem simulation where I want to save multiple outputs based on some given receiver locations in the domain. The simulation takes hours (even days on a single computer), and storing those outputs in arrays is not feasible. Additionally, I can’t store everything in one file because it will be too big and messy to read. I would like to have 20-30 files for each simulation storing different variables at different locations. I am not allocating arrays for these outputs because the size is undetermined.

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [July 7, 2022, 11:45pm UTC](https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923/2 "2022-07-07T23:45:41Z")

</div>

I fixed the comments in your code to indicate what the `end`s really correspond to.

> [@thehalfspace](#):
>
> ```julia
> function main()
> out_loc = [5.0, 10.0, 15.0, 20.0, 25.0] # This will change based on what the user wants
>     
> for i in out_loc
> open(string(out_path, "time_series_depth_",i, "km.out"), "w") do i
> write(i, "t slip sliprate shear_stress state")
> end # do
>     
> # Time loop of simulation
> while t < tmax
> for i in 1:length(out_loc)
> write(string(out_loc[i]), join(hcat(t, slip, sliprate, shear_stress, state), " "), "\n")
> end # for
>         
> end # while
>     
> # Close the files
> for i in out_loc
> end # for i in out_loc
> end # for i in out_loc
> 
> end # main
> 
> ```

Obviously there are issues here that need to be fixed. The last `for` loop is empty for example.

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [July 8, 2022, 12:13am UTC](https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923/3 "2022-07-08T00:13:09Z")

</div>

Here is the best that I can do. Basically for each element of `out_loc` we open a file, perform a simulation recording that file, and then we close the file. Then we repeat for the next element of `out_loc`.

```julia
const outpath = "/some/path"

function main()
    out_loc = [5.0, 10.0, 15.0, 20.0, 25.0] # This will change based on what the user wants
    
    # i will take on values 5, then 10, and so forth
    for i in out_loc
        open(joinpath(outpath,"time_series_depth_$i_km.out")), "w") do f
            write(f, "t slip sliprate shear_stress state")
            t = 0
            slip = 0
            shear_stress = 0
            state = 0
            while t < tmax
                t, slip, sliprate, shear_stress, state = perform_time_step(i, t, slip, shear_stress, state)
                println(f, "$t $slip $sliprate $shear_stress $state")
            end # while
        end # open ... do
    end # for
end # main

```

What is not clear to me is why you were trying to have multiple files open at the same time. Here we open one file at a time and focus on writing to that one file.

---

<div class="post-metadata">

**Author:** ![mkitti](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mkitti/32/12459_2.png) [@mkitti](https://discourse.julialang.org/u/mkitti)\
**Post date:** [July 8, 2022, 12:26am UTC](https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923/4 "2022-07-08T00:26:59Z")

</div>

Now let’s say there is some reason that you really did need all those files open at the same time.

```julia
const outpath = "/some/path"

function main()
    out_loc = [5.0, 10.0, 15.0, 20.0, 25.0] # This will change based on what the user wants
    
    # open each file, and write a header
    # i is just counting, 1, 2, 3, ...
    # o is now the values in out_loc
    for (i, o) in enumerate(out_loc)
        # no do syntax
        f[i] = open(joinpath(outpath,"time_series_depth_$o_km.out")), "w")
        write(f[i], "t slip sliprate shear_stress state")
    end

    try
        t = 0
        slip = 0
        shear_stress = 0
        state = 0
        while t < tmax
            # I am very confused about what might be happening in this loop
            for (i,o) in enumerate(out_loc)
                t, slip, sliprate, shear_stress, state = perform_time_step(o, t, slip, shear_stress, state)
                println(f[i], "$t $slip $sliprate $shear_stress $state")
            end
        end
    finally
        # close each file
        for i in 1:length(f)
            close(f[i])
        end
    end
end

```

---

<div class="post-metadata">

**Author:** ![thehalfspace](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/thehalfspace/32/7217_2.png) [@thehalfspace](https://discourse.julialang.org/u/thehalfspace)\
**Post date:** [July 8, 2022, 12:52am UTC](https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923/5 "2022-07-08T00:52:14Z")

</div>

Thanks for the response. I have a very large fem simulation where I want to save multiple outputs based on some given receiver locations in the domain. The simulation takes hours (even days on a single computer), and storing those outputs in arrays is not feasible. Additionally, I can’t store everything in one file because it will be too big and messy to read. I would like to have 20-30 files for each simulation storing different variables at different locations. I am not allocating arrays for these outputs because the size is undetermined.

---

<div class="post-metadata">

**Author:** ![thehalfspace](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/thehalfspace/32/7217_2.png) [@thehalfspace](https://discourse.julialang.org/u/thehalfspace)\
**Post date:** [July 8, 2022, 12:53am UTC](https://discourse.julialang.org/t/how-can-i-close-files-for-writing-within-a-loop/83923/6 "2022-07-08T00:53:13Z")

</div>

Thanks, this looks like exactly what I want. I’ll try it tomorrow morning and let you know how it works.