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FileSystemMap
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FileSystemMap

FileSystemMap[f,root]

gives an association whose keys are the names of files in root, and whose values are the results of applying f to the full names of these files.

FileSystemMap[f,root,n]

gives a nested association in which subdirectories down to level n are represented by an association.

FileSystemMap[f,root,{m,n}]

gives a nested association including files in subdirectories from level m down through n.

FileSystemMap[f,root,lev,r]

combines levels to give a nested output association with r levels.

Details and Options

Examples

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Basic Examples  (3)Summary of the most common use cases

Apply FileSize to all files contained in a directory:

In[1]:=1
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https://wolfram.com/xid/0b0kmowjc8o-5k7wdg
In[2]:=2
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https://wolfram.com/xid/0b0kmowjc8o-ffv41m
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0b0kmowjc8o-8ns35m

Apply FileHash to all files through level 2 of the specified directory:

In[1]:=1
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https://wolfram.com/xid/0b0kmowjc8o-if0d7t
Out[1]=1

Apply FileDate to only those files at level 2 of the specified directory:

In[1]:=1
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https://wolfram.com/xid/0b0kmowjc8o-gwj291
Out[1]=1

Get a flat association for the same directory:

In[2]:=2
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https://wolfram.com/xid/0b0kmowjc8o-hjo3pe
Out[2]=2

Options  (2)Common values & functionality for each option

FileNameForms  (1)

By default, all files are included:

In[1]:=1
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https://wolfram.com/xid/0b0kmowjc8o-d6622f
Out[1]=1

By specifying FileNameForms->patt, function application will be restricted to only those files that match the specified pattern:

In[2]:=2
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https://wolfram.com/xid/0b0kmowjc8o-bbgyi5
Out[2]=2

MaxItems  (1)

By default, f will be applied to all files in the specified directory and subdirectories:

In[1]:=1
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https://wolfram.com/xid/0b0kmowjc8o-f104x
Out[1]=1

By specifying MaxItems -> n, f will be applied to at most n items within each directory:

In[2]:=2
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https://wolfram.com/xid/0b0kmowjc8o-bd8a5e
Out[2]=2

Possible Issues  (1)Common pitfalls and unexpected behavior

When specifying a fixed number of association levels, empty directories will be omitted from the resulting association:

In[1]:=1
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https://wolfram.com/xid/0b0kmowjc8o-ebw9np
(Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0b0kmowjc8o-jwufrw
Out[2]=2
Wolfram Research (2016), FileSystemMap, Wolfram Language function, https://reference.wolfram.com/language/ref/FileSystemMap.html (updated 2019).
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Wolfram Research (2016), FileSystemMap, Wolfram Language function, https://reference.wolfram.com/language/ref/FileSystemMap.html (updated 2019).

Text

Wolfram Research (2016), FileSystemMap, Wolfram Language function, https://reference.wolfram.com/language/ref/FileSystemMap.html (updated 2019).

✖
Wolfram Research (2016), FileSystemMap, Wolfram Language function, https://reference.wolfram.com/language/ref/FileSystemMap.html (updated 2019).

CMS

Wolfram Language. 2016. "FileSystemMap." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2019. https://reference.wolfram.com/language/ref/FileSystemMap.html.

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Wolfram Language. 2016. "FileSystemMap." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2019. https://reference.wolfram.com/language/ref/FileSystemMap.html.

APA

Wolfram Language. (2016). FileSystemMap. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/FileSystemMap.html

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Wolfram Language. (2016). FileSystemMap. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/FileSystemMap.html

BibTeX

@misc{reference.wolfram_2025_filesystemmap, author="Wolfram Research", title="{FileSystemMap}", year="2019", howpublished="\url{https://reference.wolfram.com/language/ref/FileSystemMap.html}", note=[Accessed: 04-June-2025 ]}

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@misc{reference.wolfram_2025_filesystemmap, author="Wolfram Research", title="{FileSystemMap}", year="2019", howpublished="\url{https://reference.wolfram.com/language/ref/FileSystemMap.html}", note=[Accessed: 04-June-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_filesystemmap, organization={Wolfram Research}, title={FileSystemMap}, year={2019}, url={https://reference.wolfram.com/language/ref/FileSystemMap.html}, note=[Accessed: 04-June-2025 ]}

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@online{reference.wolfram_2025_filesystemmap, organization={Wolfram Research}, title={FileSystemMap}, year={2019}, url={https://reference.wolfram.com/language/ref/FileSystemMap.html}, note=[Accessed: 04-June-2025 ]}