Identify Folders in Sub-Folder

Question

I have a working directory with the following content

readdir()

6-element Vector{String}:
 "Manifest.toml"
 "Project.toml"
 "Report"
 "main.jl"
 "src"
 "test.jl"

I can identify folders here:

filter(isdir, readdir())

2-element Vector{String}:
 "Report"
 "src"

And I can show the content of the sub-folder Report:

readdir("Report/")

3-element Vector{String}:
 "jl_ACKKIu"
 "jl_zfa8Ys"
 "test.pdf"

So, why can I not identify folders in the sub-folder?

filter(isdir, readdir("Report/"))

String[]

Answer 1

readdir contains paths relative to the input directory and isdir then interprets these paths as relative to the current working directory (see pwd).

Since Julia 1.4 you can pass join=true as a keyword argument to readdir, such that the returned paths are joined with the input path:

shell> tree .
.
├── DirectoryB
│   ├── DirectoryC
│   └── FileB
└── FileA

2 directories, 2 files

julia> readdir("DirectoryB")
2-element Vector{String}:
 "DirectoryC"
 "FileB"

julia> readdir("DirectoryB"; join=true)
2-element Vector{String}:
 "DirectoryB/DirectoryC"
 "DirectoryB/FileB"

julia> filter(isdir, ans)
1-element Vector{String}:
 "DirectoryB/DirectoryC"