import-csv2

Overview

This is a PowerShell module to import CSV files. Compared to the built-in Import-Csv cmdlet, it offers the following advantages:

• Flexible parsing options: specifying delimiter/escaping/quoting characters, allowing comments, skipping blank lines, ignoring quotes, and trimming spaces.
• Various output object formats: a sequence of PSObjects, a DataTable, an OrderedDictionary, and mapping to a .NET class. These efficient object formats result in better performance and memory efficiency than the built-in cmdlet.
• Type conversion of data fields.

This module is built on top of CsvHelper, a well-known .NET library for reading and writing CSV files.

Installation

This module is published in the PowerShell Gallery

PS C:\> Install-Module import-csv2

Getting Started

This module exports a single cmdlet: Import-Csv2. By default, this cmdlet reads a CSV file and produces a sequence of PSObject objects as the built-in Import-Csv cmdlet does.

PS C:\> Import-Csv2 iris.csv | ft

Sepal.Length Sepal.Width Petal.Length Petal.Width Species
------------ ----------- ------------ ----------- -------
5.1          3.5         1.4          0.2         setosa
4.9          3           1.4          0.2         setosa
4.7          3.2         1.3          0.2         setosa
    :

The cmdlet can read data from a pipeline as the ConvertFrom-Csv cmdlet does. The following command line works just like the above.

PS C:\> Get-Content iris.csv | Import-Csv2 iris.csv | ft

With the -AsDictionary parameter, it returns an OrderedDictionary object that contains a List<T> object for each field. This option is fast to load and memory-efficient.

PS C:\> Import-Csv2 iris.csv -AsDictionary

Name                           Value
----                           -----
Sepal.Length                   {5.1, 4.9, 4.7, 4.6...}
Sepal.Width                    {3.5, 3, 3.2, 3.1...}
Petal.Length                   {1.4, 1.4, 1.3, 1.5...}
Petal.Width                    {0.2, 0.2, 0.2, 0.2...}
Species                        {setosa, setosa, setosa, setosa...}

You can also obtain a result as a DataTable object by invoking the cmdlet with -AsDataTable instead of -AsDictionary.

As another option, you can assign each record in the data to a certain .NET class by specifying the -RecordType parameter. Mapping from the header fields to the class properties can be defined in the -ColumnNameMap parameter.

PS C:\> class IrisRecord {
>>     [string]$Species
>>     [double]$SepalLength
>>     [double]$SepalWidth
>>     [double]$PetalLength
>>     [double]$PetalWidth
>> }

PS C:\> Import-Csv2 iris.csv -RecordType ([IrisRecord]) -ColumnNameMap @{
>>     "Sepal.Length" = "SepalLength"
>>     "Sepal.Width" = "SepalWidth"
>>     "Petal.Length" = "PetalLength"
>>     "Petal.Width" = "PetalWidth"
>> } | ft

Species SepalLength SepalWidth PetalLength PetalWidth
------- ----------- ---------- ----------- ----------
setosa          5.1        3.5         1.4        0.2
setosa          4.9          3         1.4        0.2
setosa          4.7        3.2         1.3        0.2
    :

Note that fields and properties with the same names are implicitly tied up.

Type conversions

You can specify field types by the -ColumnType parameter.

PS C:\> $data = import-Csv2 iris.csv -AsDictionary -ColumnTypes @{ "Sepal.Width" = [double] }

PS C:\> $data["Sepal.Width"].GetType().FullName
System.Collections.Generic.List`1[[System.Double, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

Parsing options

The following parsing options are available:

Parameter	Description
-Delimiter	Specifies a delimiter character.
-EscapeChar	Specifies a escaping character.
-QuoteChar	Specifies a quoting character.
-NoHeaderRecord	Indicates if the CSV file has a header record.
-ColumnNames	Specifies column names to override the header record.
-ColumnNameMap	Specifies mapping from the header field names to the column names of the output.
-AllowComments	Indicates to allow comments that begin with '#' by default.
-CommentChar	Specifies a comment character.
-IgnoreQuote	Indicates to ignore quoting.
-KeepBlankLines	Indicates if blank lines should be ignored when reading.
-Strict	Indicates to raise an error when the number of fields is different from that of the header record.

For the complete reference, see the help topic of the cmdlet.

License

This module is licensed under the MIT license.

The CsvHelper library included in this module is subject to its own license. Refer to the project site,