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csvstorage
CMakeLists.txt
README.md
csvstorage.c
csvstorage.h
testmod_csvstorage.c

README.md

  • infos = Information about the csvstorage plugin is in keys below
  • infos/author = Thomas Waser thomas.waser@libelektra.org
  • infos/licence = BSD
  • infos/provides = storage/csv
  • infos/needs =
  • infos/recommends =
  • infos/placements = getstorage setstorage
  • infos/status = maintained unittest nodep libc configurable limited
  • infos/description = parses CSV files

Introduction

This plugin allows you to read and write CSV files using Elektra. It aims to be compatible with RFC 4180. Rows and columns are written using Elektra's arrays (#0, #1,..). By configuring the plugin you can give columns a name.

Configuration

delimiter Tells the plugin what delimiter is used in the file. The default delimiter is , and will be used if delimiter is not set.

header Tells the plugin to use the first line as a header if it is set to colname. The columns will get the corresponding names. Skip the first line if it is set to skip or treat the first line as a record if it is set to record. If header is not set, or set to record, the columns get named #0,#1,... (array key naming)

columns If this key is set the plugin will yield an error for every file that doesn't have exactly the amount of columns as specified in columns.

columns/names Sets the column names. Only usable in combination with the columns key. The number of subkeys must match the number of columns. Conflicts with usage of header.

columns/index Specifies which column should be used to index records instead of the record number.

export=,export/<column name>= Export column column name:

  • The key export must be present, additionally to export/<column name>
  • Also multiple column names can be given for different columns to export.
    • Then delimiter will be used as delimiter (, as default).
    • The order depends on the alphabetic order of the column names. Use awk -F',' 'BEGIN{OFS=","} {print $2, $1, $3}' or similar to reorder.
    • Unknown column names are ignored.

Examples

First line should determine the headers:

kdb mount test.csv /csv csvstorage \
  "delimiter=;,header=colname,columns=2,columns/names,columns/names/#0=col0Name,columns/names/#1=col1Name"

Usage

The example below shows how you can use this plugin to read and write CSV files.

# Mount plugin to `user/tests/csv`
# We use the column names from the first line of the
# config file as key names
sudo kdb mount config.csv user/tests/csv csvstorage  "header=colname,columns/names/#0=col0Name,columns/names/#1=col1Name"

# Add some data
printf 'band,album\n'                           >> `kdb file user/tests/csv`
printf 'Converge,All We Love We Leave Behind\n' >> `kdb file user/tests/csv`
printf 'mewithoutYou,Pale Horses\n'             >> `kdb file user/tests/csv`
printf 'Kate Tempest,Everybody Down\n'          >> `kdb file user/tests/csv`

kdb ls user/tests/csv
#> user/tests/csv/#0
#> user/tests/csv/#0/album
#> user/tests/csv/#0/band
#> user/tests/csv/#1
#> user/tests/csv/#1/album
#> user/tests/csv/#1/band
#> user/tests/csv/#2
#> user/tests/csv/#2/album
#> user/tests/csv/#2/band
#> user/tests/csv/#3
#> user/tests/csv/#3/album
#> user/tests/csv/#3/band

# The first array element contains the column names
kdb get user/tests/csv/#0/band
#> band
kdb get user/tests/csv/#0/album
#> album

# Retrieve data from the last entry
kdb get user/tests/csv/#3/album
#> Everybody Down
kdb get user/tests/csv/#3/band
#> Kate Tempest

# Change an existing item
kdb set user/tests/csv/#1/album 'You Fail Me'
# Retrieve the new item
kdb get user/tests/csv/#1/album
#> You Fail Me

# The plugin stores the index of the last column
# in all of the parent keys.
kdb get user/tests/csv/#0
#> #1
kdb get user/tests/csv/#1
#> #1
kdb get user/tests/csv/#2
#> #1
kdb get user/tests/csv/#3
#> #1

# The configuration file reflects the changes
kdb file user/tests/csv | xargs cat
#> album,band
#> You Fail Me,Converge
#> Pale Horses,mewithoutYou
#> Everybody Down,Kate Tempest

# Undo changes to the key database
kdb rm -r user/tests/csv
sudo kdb umount user/tests/csv

Directory Values

By default the csvstorage plugin saves the name of the last column in each parent key. If you want to store a different value, you can do so using the Directory Value plugin.

# Mount plugin together with `directoryvalue` to `user/tests/csv`
kdb mount config.csv user/tests/csv csvstorage directoryvalue

# Add some data
printf 'Schindler’s List,1993,8.9\n'       >> `kdb file user/tests/csv`
printf 'Léon: The Professional,1994,8.5\n' >> `kdb file user/tests/csv`

# Retrieve data
kdb ls user/tests/csv
#> user/tests/csv/#0
#> user/tests/csv/#0/#0
#> user/tests/csv/#0/#1
#> user/tests/csv/#0/#2
#> user/tests/csv/#1
#> user/tests/csv/#1/#0
#> user/tests/csv/#1/#1
#> user/tests/csv/#1/#2

kdb get user/tests/csv/#0/#0
#> Schindler’s List
kdb get user/tests/csv/#1/#2
#> 8.5

# The plugin stores the index of the last column in the parent keys
kdb get user/tests/csv/#0
#> #2
kdb get user/tests/csv/#1
#> #2

# Since we use the Directory Value plugin we can also change the data in a parent key
kdb set user/tests/csv/#0 'Movie – Year – Rating'
kdb set user/tests/csv/#1 'It’s a Me.'

# Retrieve data stored in parent keys
kdb get user/tests/csv/#0
#> Movie – Year – Rating
kdb get user/tests/csv/#1
#> It’s a Me.

# Undo changes to the key database
kdb rm -r user/tests/csv
sudo kdb umount user/tests/csv

Column as index

kdb mount config.csv /tests/csv csvstorage "delimiter=;,header=colname,columns/index=IMDB"

printf 'IMDB;Title;Year\n'                          >> `kdb file /tests/csv`
printf 'tt0108052;Schindler´s List;1993\n'          >> `kdb file /tests/csv`
printf 'tt0110413;Léon: The Professional;1994\n'    >> `kdb file /tests/csv`

kdb ls /tests/csv
#> user/tests/csv/tt0108052
#> user/tests/csv/tt0108052/IMDB
#> user/tests/csv/tt0108052/Title
#> user/tests/csv/tt0108052/Year
#> user/tests/csv/tt0110413
#> user/tests/csv/tt0110413/IMDB
#> user/tests/csv/tt0110413/Title
#> user/tests/csv/tt0110413/Year

kdb get /tests/csv/tt0108052/Title
#> Schindler´s List

kdb rm -r /tests/csv
sudo kdb umount /tests/csv

Export filter

kdb mount config.csv /tests/csv csvstorage "delimiter=;,header=colname,columns/index=IMDB"

printf 'IMDB;Title;Year\n'                          >> `kdb file /tests/csv`
printf 'tt0108052;Schindler´s List;1993\n'          >> `kdb file /tests/csv`
printf 'tt0110413;Léon: The Professional;1994\n'    >> `kdb file /tests/csv`

kdb export /tests/csv csvstorage -c "delimiter=;,header=colname,columns/index=IMDB,export=,export/IMDB=,export/Title="
#> IMDB;Title
#> tt0108052;Schindler´s List
#> tt0110413;Léon: The Professional


kdb export /tests/csv csvstorage -c "delimiter=;,header=colname,columns/index=IMDB,export=,export/IMDB=,export/Year="
#> IMDB;Year
#> tt0108052;1993
#> tt0110413;1994


kdb rm -r /tests/csv
sudo kdb umount /tests/csv

Limitations

  • Does not work on file streams (e.g. kdb import without file)
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