# \`ELOOP\` when \`walkdir\`

**URL:** <https://discourse.julialang.org/t/eloop-when-walkdir/29679>\
**Category:** General Usage\
**Tags:** question\
**Created:** [October 9, 2019, 12:12pm UTC](https://discourse.julialang.org/t/eloop-when-walkdir/29679 "2019-10-09T12:12:52Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![innerlee](https://avatars.discourse-cdn.com/v4/letter/i/b19c9b/32.png) [@innerlee](https://discourse.julialang.org/u/innerlee)\
**Post date:** [October 9, 2019, 12:12pm UTC](https://discourse.julialang.org/t/eloop-when-walkdir/29679/1 "2019-10-09T12:12:52Z")

</div>

I modified the source code of [`walkdir`](https://github.com/JuliaLang/julia/blob/c6da87ff4bc7a855e217856757ad3413cf6d1f79/base/file.jl#L686-L726) a little bit to skip some irrelevant dirs. However, the code produces `ELOOP` error about when 2000 directories are processed. I do not understand the error. Is it because there are too many channels that used up the available sockets? (I have checked the dirs, actually there are almost no symbolic links). Does anyone know the direction of investigation?

```julia
ERROR: LoadError: IOError: stat: too many symbolic links encountered (ELOOP)                                                                   
Stacktrace:                                                                                                                                    
 [1] check_channel_state at ./channels.jl:125 [inlined]                                                                                        
 [2] take_unbuffered(::Channel{Any}) at ./channels.jl:327                                                                                      
 [3] take! at ./channels.jl:315 [inlined]                                                                                                      
 [4] iterate(::Channel{Any}, ::Nothing) at ./channels.jl:395                                                                                   
 [5] top-level scope at /mnt/dev/zzlistdir.jl:86 [inlined]                                                         
 [6] top-level scope at ./none:0                                                                                                               
 [7] include at ./boot.jl:326 [inlined]                                                                                                        
 [8] include_relative(::Module, ::String) at ./loading.jl:1038                                                                                 
 [9] include(::Module, ::String) at ./sysimg.jl:29                                                                                             
 [10] exec_options(::Base.JLOptions) at ./client.jl:267                                                                                        
 [11] _start() at ./client.jl:436

```

The source code is here. The main function is `walk`

```julia

STOPS_IN = ["egg-info", "backup", "torch", "tensorflow", "python", "matlab"]
PASS_EXT = [".jpg", ".png", ".avi", ".jpeg", ".tif", ".tiff", ".mp4", ".mp3", ".bmp", ".npy", ".gif", ".txt"]
FILE_EXT = [".zip", ".tar", ".tar.gz", ".rar"]

iskeepdir(d) = !any(x -> occursin(x, lowercase(d)), STOPS_IN)
iskeepfile(f) = any(x -> endswith(lowercase(f), x), FILE_EXT) 
ispasscheck(f) = any(x -> endswith(lowercase(f), x), PASS_EXT)

function walk(root)
    content = nothing
    try
        content = readdir(root)
    catch err
        c = Channel(0)
        close(c)
        return c
    end
    dirs = Vector{eltype(content)}()
    files = Vector{eltype(content)}()
    nd = 0
    for name in content
        ispasscheck(name) && continue
        if isdir(joinpath(root, name))
            iskeepdir(name) && push!(dirs, name)
        else
            iskeepfile(name) && push!(files, name)
        end
    end

    function _it(chnl)
        put!(chnl, (root, dirs, files))
        for dir in dirs
            path = joinpath(root, dir)
            if !islink(path)
                for (root_l, dirs_l, files_l) in walk(path)
                    put!(chnl, (root_l, dirs_l, files_l))
                end
            end
        end
    end

    return Channel(_it)
end

```

---

<div class="post-metadata">

**Author:** ![pixel27](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pixel27/32/8902_2.png) [@pixel27](https://discourse.julialang.org/u/pixel27)\
**Post date:** [October 10, 2019, 12:34pm UTC](https://discourse.julialang.org/t/eloop-when-walkdir/29679/2 "2019-10-10T12:34:47Z")

</div>

Sounds like you have two symbolic links pointing at each other, or multiple in bigger loop?

From: [path\_resolution(7) - Linux manual page](http://man7.org/linux/man-pages/man7/path_resolution.7.html)

> If the component is found and is a symbolic link (symlink), we first  
> resolve this symbolic link (with the current lookup directory as  
> starting lookup directory). Upon error, that error is returned. If  
> the result is not a directory, an ENOTDIR error is returned. If the  
> resolution of the symlink is successful and returns a directory, we  
> set the current lookup directory to that directory, and go to the  
> next component. Note that the resolution process here can involve  
> recursion if the prefix (‘dirname’) component of a pathname contains  
> a filename that is a symbolic link that resolves to a directory  
> (where the prefix component of that directory may contain a symbolic  
> link, and so on). In order to protect the kernel against stack  
> overflow, and also to protect against denial of service, there are  
> limits on the maximum recursion depth, and on the maximum number of  
> symbolic links followed. An ELOOP error is returned when the maximum  
> is exceeded (“Too many levels of symbolic links”).