# Ferrite.jl Stokes Flow Example: Windows-Specific File Locking Issue

**URL:** <https://discourse.julialang.org/t/ferrite-jl-stokes-flow-example-windows-specific-file-locking-issue/129099>\
**Category:** New to Julia\
**Tags:** question\
**Created:** [May 17, 2025, 1:56pm UTC](https://discourse.julialang.org/t/ferrite-jl-stokes-flow-example-windows-specific-file-locking-issue/129099 "2025-05-17T13:56:50Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![sumor](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@sumor](https://discourse.julialang.org/u/sumor)\
**Post date:** [May 17, 2025, 1:56pm UTC](https://discourse.julialang.org/t/ferrite-jl-stokes-flow-example-windows-specific-file-locking-issue/129099/1 "2025-05-17T13:56:50Z")

</div>

Hello everyone, I’m a begineer to Julia!

I’m working through the Stokes flow tutorial using Ferrite.jl and encountering an issue specifically on my Windows machine. The example code `stokes-flow.jl` runs fine on Linux (e.g., Google Colab), but fails on Windows with a `Base.IOError`.

The error occurs during the mesh generation phase, specifically when writing and reading the mesh file within the `setup_grid` function. The error message is:

```julia
Warning: Failed to clean up temporary path "C:\\Users\\summer\\AppData\\Local\\Temp\\jl_nkR4Ag"
│ Base.IOError("unlink(\"C:\\\\Users\\\\summer\\\\AppData\\\\Local\\\\Temp\\\\jl_nkR4Ag\\\\mesh.msh\"): resource busy or locked (EBUSY)", -4082)

```

Here’s the complete `setup_grid` function where the error occurs:

```julia
function setup_grid(h = 0.05)
    # Initialize gmsh
    Gmsh.initialize()
    gmsh.option.set_number("General.Verbosity", 2)

    # Add the points
    o = gmsh.model.geo.add_point(0.0, 0.0, 0.0, h)
    p1 = gmsh.model.geo.add_point(0.5, 0.0, 0.0, h)
    p2 = gmsh.model.geo.add_point(1.0, 0.0, 0.0, h)
    p3 = gmsh.model.geo.add_point(0.0, 1.0, 0.0, h)
    p4 = gmsh.model.geo.add_point(0.0, 0.5, 0.0, h)

    # Add the lines
    l1 = gmsh.model.geo.add_line(p1, p2)
    l2 = gmsh.model.geo.add_circle_arc(p2, o, p3)
    l3 = gmsh.model.geo.add_line(p3, p4)
    l4 = gmsh.model.geo.add_circle_arc(p4, o, p1)

    # Create the closed curve loop and the surface
    loop = gmsh.model.geo.add_curve_loop([l1, l2, l3, l4])
    surf = gmsh.model.geo.add_plane_surface([loop])

    # Synchronize the model
    gmsh.model.geo.synchronize()

    # Create the physical domains
    gmsh.model.add_physical_group(1, [l1], -1, "Γ1")
    gmsh.model.add_physical_group(1, [l2], -1, "Γ2")
    gmsh.model.add_physical_group(1, [l3], -1, "Γ3")
    gmsh.model.add_physical_group(1, [l4], -1, "Γ4")
    gmsh.model.add_physical_group(2, [surf])

    # Add the periodicity constraint using 4x4 affine transformation matrix,
    # see https://en.wikipedia.org/wiki/Transformation_matrix#Affine_transformations
    transformation_matrix = zeros(4, 4)
    transformation_matrix[1, 2] = 1 # -sin(-pi/2)
    transformation_matrix[2, 1] = -1 # cos(-pi/2)
    transformation_matrix[3, 3] = 1
    transformation_matrix[4, 4] = 1
    transformation_matrix = vec(transformation_matrix')
    gmsh.model.mesh.set_periodic(1, [l1], [l3], transformation_matrix)

    # Generate a 2D mesh
    gmsh.model.mesh.generate(2)

    # Save the mesh, and read back in as a Ferrite Grid
    grid = mktempdir() do dir
        path = joinpath(dir, "mesh.msh")
        gmsh.write(path)
        togrid(path)
    end

    # # Finalize the Gmsh library
    Gmsh.finalize()

    
    return grid
end

```

The problematic part seems to be within the `mktempdir()` block where the `mesh.msh` file is written and then read back in using `togrid()`. The error suggests that the file is locked or busy when the `mktempdir()` tries to clean up.

Has anyone experienced this specific issue on Windows when working with Gmsh and Ferrite.jl for mesh generation? Any suggestions for resolving this file locking problem would be greatly appreciated. The full error message is below:

```julia
Error: mktempdir cleanup
│ exception =
│ IOError: unlink("C:\\Users\\summer\\AppData\\Local\\Temp\\jl_nkR4Ag\\mesh.msh"): resource busy or locked (EBUSY)
│ Stacktrace:
│ [1] uv_error
│ @ .\libuv.jl:100 [inlined]
│ [2] unlink(p::String)
│ @ Base.Filesystem .\file.jl:978
│ [3] rm(path::String; force::Bool, recursive::Bool)
│ @ Base.Filesystem .\file.jl:283
│ [4] rm(path::String; force::Bool, recursive::Bool)
│ @ Base.Filesystem .\file.jl:294
│ [5] rm
│ @ .\file.jl:273 [inlined]
│ [6] mktempdir(fn::var"#1#2", parent::String; prefix::String)
│ @ Base.Filesystem .\file.jl:771
│ [7] mktempdir (repeats 2 times)
│ @ .\file.jl:762 [inlined]
│ [8] setup_grid(h::Float64)
│ @ Main d:\Users\summer\Desktop\5\stokes-flow(plain).jl:49
│ [9] main()
│ @ Main d:\Users\summer\Desktop\5\stokes-flow(plain).jl:198
│ [10] top-level scope
│ @ d:\Users\summer\Desktop\5\stokes-flow(plain).jl:228
│ [11] include(mod::Module, _path::String)
│ @ Base .\Base.jl:495
│ [12] exec_options(opts::Base.JLOptions)
│ @ Base .\client.jl:323
│ [13] _start()
│ @ Base .\client.jl:557
└ @ Base.Filesystem file.jl:774
ERROR: LoadError: 
Stacktrace:
  [1] error(s::String)
    @ Base .\error.jl:35
  [2] open(fileName::String)
    @ Gmsh.gmsh D:\MySoftware\Julia\packages\artifacts\649584fb27316a4395dbb47fde904c83626feae5\lib\gmsh.jl:113
  [3] togrid(filename::String; domain::String)
    @ FerriteGmsh D:\MySoftware\Julia\packages\packages\FerriteGmsh\MH6r7\src\FerriteGmsh.jl:185
  [4] togrid
    @ D:\MySoftware\Julia\packages\packages\FerriteGmsh\MH6r7\src\FerriteGmsh.jl:176 [inlined]
  [5] #1
    @ d:\Users\summer\Desktop\5\stokes-flow(plain).jl:52 [inlined]
  [6] mktempdir(fn::var"#1#2", parent::String; prefix::String)
    @ Base.Filesystem .\file.jl:766
  [7] mktempdir (repeats 2 times)
    @ .\file.jl:762 [inlined]
  [8] setup_grid(h::Float64)
    @ Main d:\Users\summer\Desktop\5\stokes-flow(plain).jl:49
  [9] main()
    @ Main d:\Users\summer\Desktop\5\stokes-flow(plain).jl:198
 [10] top-level scope
    @ d:\Users\summer\Desktop\5\stokes-flow(plain).jl:228
in expression starting at d:\Users\summer\Desktop\5\stokes-flow(plain).jl:228        
┌ Warning: Failed to clean up temporary path "C:\\Users\\summer\\AppData\\Local\\Temp\\jl_nkR4Ag"
│ Base.IOError("unlink(\"C:\\\\Users\\\\summer\\\\AppData\\\\Local\\Temp\\jl_nkR4Ag\\\\mesh.msh\"): resource busy or locked (EBUSY)", -4082)
└ @ Base.Filesystem file.jl:549

```

I hope someone can help! Thanks in advance.

---

<div class="post-metadata">

**Author:** ![sumor](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@sumor](https://discourse.julialang.org/u/sumor)\
**Post date:** [May 17, 2025, 3:33pm UTC](https://discourse.julialang.org/t/ferrite-jl-stokes-flow-example-windows-specific-file-locking-issue/129099/2 "2025-05-17T15:33:00Z")

</div>

The total code can be found in Ferrite → Tutorials → Stokes flow

---

<div class="post-metadata">

**Author:** ![KnutAM](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/knutam/32/37720_2.png) [@KnutAM](https://discourse.julialang.org/u/KnutAM)\
**Post date:** [May 19, 2025, 4:41am UTC](https://discourse.julialang.org/t/ferrite-jl-stokes-flow-example-windows-specific-file-locking-issue/129099/3 "2025-05-19T04:41:49Z")

</div>

Welcome @sumor !

Unfortunately, Gmsh.jl is still not stable on Windows as far as I know. But it is possible to use WSL.

---

<div class="post-metadata">

**Author:** ![sumor](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@sumor](https://discourse.julialang.org/u/sumor)\
**Post date:** [May 27, 2025, 2:43am UTC](https://discourse.julialang.org/t/ferrite-jl-stokes-flow-example-windows-specific-file-locking-issue/129099/4 "2025-05-27T02:43:28Z")

</div>

One solution is to avoid saving the mesh. That is, replace:

```julia
# Save the mesh, and read back in as a Ferrite Grid
grid = mktempdir() do dir
    path = joinpath(dir, "mesh.msh")
    gmsh.write(path)
    togrid(path)
end

```

with simply:

```julia
# Skip file I/O and convert GMSH data directly to Ferrite Grid
grid = togrid()

```