xan, the CSV magician

xan is a command line tool that can be used to process CSV files directly from the shell.

It has been written in Rust to be as fast as possible, use as little memory as possible, and can easily handle very large CSV files (Gigabytes). It is also able to leverage parallelism (through multithreading) to make some tasks complete as fast as your computer can allow.

It can easily preview, filter, slice, aggregate, sort, join CSV files, and exposes a large collection of composable commands that can be chained together to perform a wide variety of typical tasks.

xan also leverages its own expression language so you can perform complex tasks that cannot be done by relying on the simplest commands. This minimalistic language has been tailored for CSV data and is faster than evaluating typical dynamically-typed languages such as Python, Lua, JavaScript etc.

Note that this tool is originally a fork of BurntSushi's xsv, but has been nearly entirely rewritten at that point, to fit SciencesPo's médialab use-cases, rooted in web data collection and analysis geared towards social sciences (you might think CSV is outdated by now, but read our love letter to the format before judging too quickly).

Finally, xan can be used to display CSV files in the terminal, for easy exploration, and can even be used to draw basic data visualisations:

view command	flatten command
categorical histogram	scatterplot
categorical scatterplot	histograms
parallel processing	time series
small multiples (facet grid)	grouped view

Summary

• How to install
• Quick tour
• Available commands
• General flags and IO model
• Expression language reference
• Advanced use-cases
• Frequently Asked Questions

How to install

xan can be installed using cargo (it usually comes with Rust):

cargo install xan

You can also install the latest dev version thusly:

cargo install --git https://github.com/medialab/xan

Note that xan also exposes handy automatic completions for command and header names that you can install through the xan completions command.

Run the following command to understand how to install those completions:

xan completions -h

Quick tour

Let's learn about the most commonly used xan commands by exploring a corpus of French medias:

Downloading the corpus

curl -LO https://github.com/medialab/corpora/raw/master/polarisation/medias.csv

Displaying the file's headers

xan headers medias.csv

0   webentity_id
1   name
2   prefixes
3   home_page
4   start_pages
5   indegree
6   hyphe_creation_timestamp
7   hyphe_last_modification_timestamp
8   outreach
9   foundation_year
10  batch
11  edito
12  parody
13  origin
14  digital_native
15  mediacloud_ids
16  wheel_category
17  wheel_subcategory
18  has_paywall
19  inactive

Counting the number of rows

xan count medias.csv

478

Previewing the file in the terminal

xan view medias.csv

Displaying 5/20 cols from 10 first rows of medias.csv
┌───┬───────────────┬───────────────┬────────────┬───┬─────────────┬──────────┐
│ - │ name          │ prefixes      │ home_page  │ … │ has_paywall │ inactive │
├───┼───────────────┼───────────────┼────────────┼───┼─────────────┼──────────┤
│ 0 │ Acrimed.org   │ http://acrim… │ http://ww… │ … │ false       │ <empty>  │
│ 1 │ 24matins.fr   │ http://24mat… │ https://w… │ … │ false       │ <empty>  │
│ 2 │ Actumag.info  │ http://actum… │ https://a… │ … │ false       │ <empty>  │
│ 3 │ 2012un-Nouve… │ http://2012u… │ http://ww… │ … │ false       │ <empty>  │
│ 4 │ 24heuresactu… │ http://24heu… │ http://24… │ … │ false       │ <empty>  │
│ 5 │ AgoraVox      │ http://agora… │ http://ww… │ … │ false       │ <empty>  │
│ 6 │ Al-Kanz.org   │ http://al-ka… │ https://w… │ … │ false       │ <empty>  │
│ 7 │ Alalumieredu… │ http://alalu… │ http://al… │ … │ false       │ <empty>  │
│ 8 │ Allodocteurs… │ http://allod… │ https://w… │ … │ false       │ <empty>  │
│ 9 │ Alterinfo.net │ http://alter… │ http://ww… │ … │ <empty>     │ true     │
│ … │ …             │ …             │ …          │ … │ …           │ …        │
└───┴───────────────┴───────────────┴────────────┴───┴─────────────┴──────────┘

On unix, don't hesitate to use the -p flag to automagically forward the full output to an appropriate pager and skim through all the columns.

Reading a flattened representation of the first row

# NOTE: drop -c to avoid truncating the values
xan flatten -c medias.csv

Row n°0
───────────────────────────────────────────────────────────────────────────────
webentity_id                      1
name                              Acrimed.org
prefixes                          http://acrimed.org|http://acrimed69.blogspot…
home_page                         http://www.acrimed.org
start_pages                       http://acrimed.org|http://acrimed69.blogspot…
indegree                          61
hyphe_creation_timestamp          1560347020330
hyphe_last_modification_timestamp 1560526005389
outreach                          nationale
foundation_year                   2002
batch                             1
edito                             media
parody                            false
origin                            france
digital_native                    true
mediacloud_ids                    258269
wheel_category                    Opinion Journalism
wheel_subcategory                 Left Wing
has_paywall                       false
inactive                          <empty>

Row n°1
───────────────────────────────────────────────────────────────────────────────
webentity_id                      2
...

Searching for rows

xan search -s outreach internationale medias.csv | xan view

Displaying 4/20 cols from 10 first rows of <stdin>
┌───┬──────────────┬────────────────────┬───┬─────────────┬──────────┐
│ - │ webentity_id │ name               │ … │ has_paywall │ inactive │
├───┼──────────────┼────────────────────┼───┼─────────────┼──────────┤
│ 0 │ 25           │ Businessinsider.fr │ … │ false       │ <empty>  │
│ 1 │ 59           │ Europe-Israel.org  │ … │ false       │ <empty>  │
│ 2 │ 66           │ France 24          │ … │ false       │ <empty>  │
│ 3 │ 220          │ RFI                │ … │ false       │ <empty>  │
│ 4 │ 231          │ fr.Sott.net        │ … │ false       │ <empty>  │
│ 5 │ 246          │ Voltairenet.org    │ … │ true        │ <empty>  │
│ 6 │ 254          │ Afp.com /fr        │ … │ false       │ <empty>  │
│ 7 │ 265          │ Euronews FR        │ … │ false       │ <empty>  │
│ 8 │ 333          │ Arte.tv            │ … │ false       │ <empty>  │
│ 9 │ 341          │ I24News.tv         │ … │ false       │ <empty>  │
│ … │ …            │ …                  │ … │ …           │ …        │
└───┴──────────────┴────────────────────┴───┴─────────────┴──────────┘

Selecting some columns

xan select foundation_year,name medias.csv | xan view

Displaying 2 cols from 10 first rows of <stdin>
┌───┬─────────────────┬───────────────────────────────────────┐
│ - │ foundation_year │ name                                  │
├───┼─────────────────┼───────────────────────────────────────┤
│ 0 │ 2002            │ Acrimed.org                           │
│ 1 │ 2006            │ 24matins.fr                           │
│ 2 │ 2013            │ Actumag.info                          │
│ 3 │ 2012            │ 2012un-Nouveau-Paradigme.com          │
│ 4 │ 2010            │ 24heuresactu.com                      │
│ 5 │ 2005            │ AgoraVox                              │
│ 6 │ 2008            │ Al-Kanz.org                           │
│ 7 │ 2012            │ Alalumieredunouveaumonde.blogspot.com │
│ 8 │ 2005            │ Allodocteurs.fr                       │
│ 9 │ 2005            │ Alterinfo.net                         │
│ … │ …               │ …                                     │
└───┴─────────────────┴───────────────────────────────────────┘

Sorting the file

xan sort -s foundation_year medias.csv | xan view -s name,foundation_year

Displaying 2 cols from 10 first rows of <stdin>
┌───┬────────────────────────────────────┬─────────────────┐
│ - │ name                               │ foundation_year │
├───┼────────────────────────────────────┼─────────────────┤
│ 0 │ Le Monde Numérique (Ouest France)  │ <empty>         │
│ 1 │ Le Figaro                          │ 1826            │
│ 2 │ Le journal de Saône-et-Loire       │ 1826            │
│ 3 │ L'Indépendant                      │ 1846            │
│ 4 │ Le Progrès                         │ 1859            │
│ 5 │ La Dépêche du Midi                 │ 1870            │
│ 6 │ Le Pélerin                         │ 1873            │
│ 7 │ Dernières Nouvelles d'Alsace (DNA) │ 1877            │
│ 8 │ La Croix                           │ 1883            │
│ 9 │ Le Chasseur Francais               │ 1885            │
│ … │ …                                  │ …               │
└───┴────────────────────────────────────┴─────────────────┘

Deduplicating the file on some column

# Some medias of our corpus have the same ids on mediacloud.org
xan dedup -s mediacloud_ids medias.csv | xan count && xan count medias.csv

457
478

Deduplicating can also be done while sorting:

xan sort -s mediacloud_ids -u medias.csv

Computing frequency tables

xan frequency -s edito medias.csv | xan view

Displaying 3 cols from 5 rows of <stdin>
┌───┬───────┬────────────┬───────┐
│ - │ field │ value      │ count │
├───┼───────┼────────────┼───────┤
│ 0 │ edito │ media      │ 423   │
│ 1 │ edito │ individu   │ 30    │
│ 2 │ edito │ plateforme │ 14    │
│ 3 │ edito │ agrégateur │ 10    │
│ 4 │ edito │ agence     │ 1     │
└───┴───────┴────────────┴───────┘

Printing a histogram

xan frequency -s edito medias.csv | xan hist

Histogram for edito (bars: 5, sum: 478, max: 423):

media      |423  88.49%|━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━|
individu   | 30   6.28%|━━━╸                                                  |
plateforme | 14   2.93%|━╸                                                    |
agrégateur | 10   2.09%|━╸                                                    |
agence     |  1   0.21%|╸                                                     |

Computing descriptive statistics

xan stats -s indegree,edito medias.csv | xan transpose | xan view -I

Displaying 2 cols from 14 rows of <stdin>
┌─────────────┬───────────────────┬────────────┐
│ field       │ indegree          │ edito      │
├─────────────┼───────────────────┼────────────┤
│ count       │ 463               │ 478        │
│ count_empty │ 15                │ 0          │
│ type        │ int               │ string     │
│ types       │ int|empty         │ string     │
│ sum         │ 25987             │ <empty>    │
│ mean        │ 56.12742980561554 │ <empty>    │
│ variance    │ 4234.530197929737 │ <empty>    │
│ stddev      │ 65.07326792108829 │ <empty>    │
│ min         │ 0                 │ <empty>    │
│ max         │ 424               │ <empty>    │
│ lex_first   │ 0                 │ agence     │
│ lex_last    │ 99                │ plateforme │
│ min_length  │ 0                 │ 5          │
│ max_length  │ 3                 │ 11         │
└─────────────┴───────────────────┴────────────┘

Evaluating an expression to filter a file

xan filter 'batch > 1' medias.csv | xan count

130

To access the expression language's cheatsheet, run xan filter --cheatsheet. To display the full list of available functions, run xan filter --functions.

Evaluating an expression to create a new column based on other ones

xan map 'fmt("{} ({})", name, foundation_year)' key medias.csv | xan select key | xan slice -l 10

key
Acrimed.org (2002)
24matins.fr (2006)
Actumag.info (2013)
2012un-Nouveau-Paradigme.com (2012)
24heuresactu.com (2010)
AgoraVox (2005)
Al-Kanz.org (2008)
Alalumieredunouveaumonde.blogspot.com (2012)
Allodocteurs.fr (2005)
Alterinfo.net (2005)

To access the expression language's cheatsheet, run xan map --cheatsheet. To display the full list of available functions, run xan map --functions.

Transform a column by evaluating an expression

xan transform name 'split(name, ".") | first | upper' medias.csv | xan select name | xan slice -l 10

name
ACRIMED
24MATINS
ACTUMAG
2012UN-NOUVEAU-PARADIGME
24HEURESACTU
AGORAVOX
AL-KANZ
ALALUMIEREDUNOUVEAUMONDE
ALLODOCTEURS
ALTERINFO

To access the expression language's cheatsheet, run xan transform --cheatsheet. To display the full list of available functions, run xan transform --functions.

Performing custom aggregation

xan agg 'sum(indegree) as total_indegree, mean(indegree) as mean_indegree' medias.csv | xan view -I

Displaying 1 col from 1 rows of <stdin>
┌────────────────┬───────────────────┐
│ total_indegree │ mean_indegree     │
├────────────────┼───────────────────┤
│ 25987          │ 56.12742980561554 │
└────────────────┴───────────────────┘

To access the expression language's cheatsheet, run xan agg --cheatsheet. To display the full list of available functions, run xan agg --functions. Finally, to display the list of available aggregation functions, run xan agg --aggs.

Grouping rows and performing per-group aggregation

xan groupby edito 'sum(indegree) as indegree' medias.csv | xan view -I

Displaying 1 col from 5 rows of <stdin>
┌────────────┬──────────┐
│ edito      │ indegree │
├────────────┼──────────┤
│ agence     │ 50       │
│ agrégateur │ 459      │
│ plateforme │ 658      │
│ media      │ 24161    │
│ individu   │ 659      │
└────────────┴──────────┘

To access the expression language's cheatsheet, run xan groupby --cheatsheet. To display the full list of available functions, run xan groupby --functions. Finally, to display the list of available aggregation functions, run xan groupby --aggs.

Available commands

All commands are not fully documented on this README yet, but all the necessary information can be found directly from the command line. Just run xan command -h for help

Explore & visualize

• count (c): Count rows in file
• headers (h): Show header names
• view (v): Preview a CSV file in a human-friendly way
• flatten: Display a flattened version of each row of a file
• hist: Print a histogram with rows of CSV file as bars
• plot: Draw a scatter plot or line chart
• heatmap: Draw a heatmap of a CSV matrix
• progress: Display a progress bar while reading CSV data

Search & filter

• search: Search CSV data with regexes
• filter: Only keep some CSV rows based on an evaluated expression
• slice: Slice rows of CSV file
• top: Find top rows of a CSV file according to some column
• sample: Randomly sample CSV data

Sort & deduplicate

• sort: Sort CSV data
• dedup: Deduplicate a CSV file
• shuffle: Shuffle CSV data

Aggregate

• frequency (freq): Show frequency tables
• groupby: Aggregate data by groups of a CSV file
• stats: Compute basic statistics
• agg: Aggregate data from CSV file
• bins: Dispatch numeric columns into bins

Combine multiple CSV files

• cat: Concatenate by row or column
• join: Join CSV files
• merge: Merge multiple similar already sorted CSV files

Add, transform, drop and move columns

• select: Select columns from a CSV file
• drop: Drop columns from a CSV file
• map: Create a new column by evaluating an expression on each CSV row
• transform: Transform a column by evaluating an expression on each CSV row
• enum: Enumerate CSV file by preprending an index column
• flatmap: Emit one row per value yielded by an expression evaluated for each CSV row
• fill: Fill empty cells
• blank: Blank down contiguous identical cell values

Format, convert & recombobulate

• behead: Drop header from CSV file
• rename: Rename columns of a CSV file
• input: Read CSV data with special quoting rules
• fixlengths: Makes all rows have same length
• fmt: Format CSV output (change field delimiter)
• explode: Explode rows based on some column separator
• implode: Collapse consecutive identical rows based on a diverging column
• from: Convert a variety of formats to CSV
• to: Convert a CSV file to a variety of data formats
• reverse: Reverse rows of CSV data
• transpose: Transpose CSV file

Split a CSV file into multiple

• split: Split CSV data into chunks
• partition: Partition CSV data based on a column value

Parallel operation over multiple CSV files

• parallel (p): Map-reduce-like parallel computation over multiple CSV files

Generate CSV files

• glob: Create a CSV file with paths matching a glob pattern
• range: Create a CSV file from a numerical range

Perform side-effects

• foreach: Loop over a CSV file to perform side effects

Lexicometry & fuzzy matching

• tokenize: Tokenize a text column
• vocab: Build a vocabulary over tokenized documents
• cluster: Cluster CSV data to find near-duplicates

Matrix & network-related commands

• matrix: Convert CSV data to matrix data
• network: Convert CSV data to network data
• union-find: Apply the union-find algorithm on a CSV edge list

General flags and IO model

Getting help

If you ever feel lost, each command has a -h/--help flag that will print the related documentation.

Regarding input & output formats

All xan commands expect a "standard" CSV file, e.g. comma-delimited, with proper double-quote escaping. This said, xan is also perfectly able to infer the delimiter from typical file extensions such as .tsv or .tab.

If you need to process a file with a custom delimiter, you can either use the xan input command or use the -d/--delimiter flag available with all commands.

If you need to output a custom CSV dialect (e.g. using ; delimiters), feel free to use the xan fmt command.

Finally, even if most xan commands won't even need to decode the file's bytes, some might still need to. In this case, xan will expect correctly formatted UTF-8 text. Please use iconv or other utils if you need to process other encodings such as latin1 ahead of xan.

Working with headless CSV file

Even if this is good practice to name your columns, some CSV file simply don't have headers. Most commands are able to deal with those file if you give the -n/--no-headers flag.

Note that this flag always relates to the input, not the output. If for some reason you want to drop a CSV output's header row, use the xan behead command.

Regarding stdin

By default, all commands will try to read from stdin when the file path is not specified. This makes piping easy and comfortable as it respects typical unix standards. Some commands may have multiple inputs (xan join, for instance), in which case stdin is usually specifiable using the - character:

# First file given to join will be read from stdin
cat file1.csv | xan join col1 - col2 file2.csv

Note that the command will also warn you when stdin cannot be read, in case you forgot to indicate the file's path.

Regarding stdout

By default, all commands will print their output to stdout (note that this output is usually buffered for performance reasons).

In addition, all commands expose a -o/--output flag that can be use to specify where to write the output. This can be useful if you do not want to or cannot use > (typically in some Windows shells). In which case, - as a output path will mean forwarding to stdout also. This can be useful when scripting sometimes.

Gzipped files

xan is able to read gzipped files (having a .gz extension) out of the box.

Expression language reference

xan expression language API reference

Advanced use-cases

Reading files in parallel

Let's say one column of your CSV file is containing paths to files, relative to some downloaded folder, and you want to make sure all of them contain some string (maybe you crawled some website and want to make sure you were correctly logged in by searching for some occurrence of your username):

xan progress files.csv | \
xan filter -p 'pathjoin("downloaded", path) | read | !contains(_, /yomguithereal/i)' > not-logged.csv

Generating a CSV of paginated urls to download

Let's say you want to download the latest 50 pages from Hacker News using another of our tools named minet.

You can pipe xan range into xan select -e into minet fetch:

xan range -s 1 50 -i | \
xan select -e '"https://news.ycombinator.com/?p=".n as url' | \
minet fetch url -i -

Piping to xargs

Let's say you want to delete all files whose path can be found in a column of CSV file. You can select said column and format it with xan before piping to xargs:

xan select path files.csv | \
xan behead | \
xan fmt --quote-never | \
xargs -I {} rm {};

Frequently Asked Questions

How to display a vertical bar chart?

Rotate your screen ;)