Comma Separated Value (.csv)

Driver short name

CSV

Driver built-in by default

This driver is built-in by default

OGR supports reading and writing primarily non-spatial tabular data stored in text CSV files. CSV files are a common interchange format between software packages supporting tabular data and are also easily produced manually with a text editor or with end-user written scripts or programs.

The datasource name may be either a single CSV file or point to a directory. For a directory to be recognised as a .csv datasource at least half the files in the directory need to have the extension .csv. One layer (table) is produced from each .csv file accessed. Starting with GDAL 3.7, pipe separated values files with a ".psv" extension are also recognized.

For files structured as CSV, but not ending with the ".csv" extension, the 'CSV:' prefix can be added before the filename to force loading by the CSV driver.

Starting with GDAL 3.10, specifying the -if CSV option to command line utilities accepting it, or CSV as the only value of the papszAllowedDrivers of GDALOpenEx(), also forces the driver to recognize the passed filename, without the CSV: prefix.

The OGR CSV driver supports reading and writing. Because the CSV format has variable length text lines, reading is done sequentially. Reading features in random order will generally be very slow. OGR CSV layer might have a coordinate system stored in a .prj file (see GeoCSV specification). When reading a field named "WKT" is assumed to contain WKT geometry, but also is treated as a regular field. The OGR CSV driver returns all attribute columns as string data types if no field type information file (with .csvt extension) is available.

Limited type recognition can be done for Integer, Real, String, Date (YYYY-MM-DD), Time (HH:MM:SS+nn), DateTime (YYYY-MM-DD HH:MM:SS+nn) columns through a descriptive file with the same name as the CSV file, but a .csvt extension. In a single line the types for each column have to be listed with double quotes and be comma separated (e.g., "Integer","String"). It is also possible to specify explicitly the width and precision of each column, e.g. "Integer(5)","Real(10.7)","String(15)". The driver will then use these types as specified for the csv columns. Subtypes can be passed between parenthesis, such as "Integer(Boolean)", "Integer(Int16)" and "Real(Float32)". Starting with GDAL 2.1, accordingly with the GeoCSV specification, the "CoordX" or "Point(X)" type can be used to specify a column with longitude/easting values, "CoordY" or "Point(Y)" for latitude/northing values and "WKT" for geometries encoded in WKT

Starting with GDAL 2.2, the "JSonStringList", "JSonIntegerList", "JSonInteger64List" and "JSonRealList" types can be used in .csvt to map to the corresponding OGR StringList, IntegerList, Integer64List and RealList types. The field values are then encoded as JSON arrays, with proper CSV escaping.

Automatic field type guessing can also be done if specifying the open options described in the below "Open options" section.

Driver capabilities

Supports Create()

This driver supports the GDALDriver::Create() operation

Supports Georeferencing

This driver supports georeferencing

Supports VirtualIO

This driver supports virtual I/O operations (/vsimem/, etc.)

Format

CSV files have one line for each feature (record) in the layer (table). The attribute field values are separated by commas. At least two fields per line must be present. Lines may be terminated by a DOS (CR/LF) or Unix (LF) style line terminators. Each record should have the same number of fields. The driver will also accept a semicolon, a tabulation, a pipe, or a space character as field separator. Starting with GDAL 3.8, the autodection will select the separator with the most occurrences if there are several candidates on the first line of the CSV file (and warn about that). The SEPARATOR open option may also be set to define the desired separator. Previous versions select comma by default when there are several potential separators.

Complex attribute values (such as those containing commas, quotes or newlines) may be placed in double quotes. Any occurrences of double quotes within the quoted string should be doubled up to "escape" them.

By default, the driver attempts to treat the first line of the file as a list of field names for all the fields. However, if one or more of the names is all numeric it is assumed that the first line is actually data values and dummy field names are generated internally (field_1 through field_n) and the first record is treated as a feature. Numeric values are treated as field names if they are enclosed in double quotes. Starting with GDAL 2.1, this behavior can be modified via the HEADERS open option.

All CSV files are treated as UTF-8 encoded. A Byte Order Mark (BOM) at the beginning of the file will be parsed correctly. The layer creation option WRITE_BOM can be used to create a file with a Byte Order Mark, which can improve compatibility with some software (particularly Excel).

Example (employee.csv):

ID,Salary,Name,Comments
132,55000.0,John Walker,"The ""big"" cheese."
133,11000.0,Jane Lake,Cleaning Staff

Note that the Comments value for the first data record is placed in double quotes because the value contains quotes, and those quotes have to be doubled up so we know we haven't reached the end of the quoted string yet.

Many variations of textual input are sometimes called Comma Separated Value files, including files without commas, but fixed column widths, those using tabs as separators or those with other auxiliary data defining field types or structure. This driver does not attempt to support all such files, but instead to support simple .csv files that can be auto-recognised. Scripts or other mechanisms can generally be used to convert other variations into a form that is compatible with the OGR CSV driver.

Reading CSV containing spatial information

Building point geometries

Consider the following CSV file (test.csv):

Latitude,Longitude,Name
48.1,0.25,"First point"
49.2,1.1,"Second point"
47.5,0.75,"Third point"

Starting with GDAL 2.1, it is possible to directly specify the potential names of the columns that can contain X/longitude and Y/latitude with the X_POSSIBLE_NAMES and Y_POSSIBLE_NAMES open option.

ogrinfo -ro -al test.csv -oo X_POSSIBLE_NAMES=Lon* -oo Y_POSSIBLE_NAMES=Lat* -oo KEEP_GEOM_COLUMNS=NO will return :

OGRFeature(test):1
  Name (String) = First point
  POINT (0.25 48.1)

OGRFeature(test):2
  Name (String) = Second point
  POINT (1.1 49.2)

OGRFeature(test):3
  Name (String) = Third point
  POINT (0.75 47.5)

If the CSV file does not have a header line, the dummy "field_n" names can be used as possible names for coordinate fields. For example plain XYZ point data can be opened as

ogrinfo -ro -al elevation.xyz -oo X_POSSIBLE_NAMES=field_1 -oo Y_POSSIBLE_NAMES=field_2 -oo Z_POSSIBLE_NAMES=field_3

Otherwise, if one or several columns contain a geometry definition encoded as WKT, WKB (encoded in hexadecimal) or GeoJSON (in which case the GeoJSON content must be formatted to follow CSV rules, that is to say it must be surrounded by double-quotes, and double-quotes inside the string must be repeated for proper escaping), the name of such column(s) can be derived from the GEOM_POSSIBLE_NAMES open option.

For older versions, it is possible to extract spatial information (points) from a CSV file which has columns for the X and Y coordinates, through the use of the VRT driver.

You can write the associated VRT file (test.vrt):

<OGRVRTDataSource>
    <OGRVRTLayer name="test">
        <SrcDataSource>test.csv</SrcDataSource>
        <GeometryType>wkbPoint</GeometryType>
        <LayerSRS>WGS84</LayerSRS>
        <GeometryField encoding="PointFromColumns" x="Longitude" y="Latitude"/>
    </OGRVRTLayer>
</OGRVRTDataSource>

and ogrinfo -ro -al test.vrt will return :

OGRFeature(test):1
  Latitude (String) = 48.1
  Longitude (String) = 0.25
  Name (String) = First point
  POINT (0.25 48.1 0)

OGRFeature(test):2
  Latitude (String) = 49.2
  Longitude (String) = 1.1
  Name (String) = Second point
  POINT (1.1 49.200000000000003 0)

OGRFeature(test):3
  Latitude (String) = 47.5
  Longitude (String) = 0.75
  Name (String) = Third point
  POINT (0.75 47.5 0)

Building line geometries

Consider the following CSV file (test.csv):

way_id,pt_id,x,y
1,1,2,49
1,2,3,50
2,1,-2,49
2,2,-3,50

With a GDAL build with Spatialite enabled, ogrinfo test.csv -dialect SQLite -sql "SELECT way_id, MakeLine(MakePoint(CAST(x AS float),CAST(y AS float))) FROM test GROUP BY way_id" will return :

OGRFeature(SELECT):0
  way_id (String) = 1
  LINESTRING (2 49,3 50)

OGRFeature(SELECT):1
  way_id (String) = 2
  LINESTRING (-2 49,-3 50)

VSI Virtual File System API support

The driver supports reading and writing to files managed by VSI Virtual File System API, which include "regular" files, as well as files in the /vsizip/ (read-write) , /vsigzip/ (read-only) , /vsicurl/ (read-only) domains.

Writing to /dev/stdout or /vsistdout/ is also supported.

Reading from /vsistdin/ is supported using the CSV:/vsistdin/ connection string and provided that none of the open options whose name starts with AUTODETECT_ is used.

Open options

Open options can be specified in command-line tools using the syntax -oo <NAME>=<VALUE> or by providing the appropriate arguments to GDALOpenEx() (C) or gdal.OpenEx (Python). The following open options are supported:

  • SEPARATOR=[AUTO/COMMA/SEMICOLON/TAB/SPACE/PIPE]: (GDAL >= 3.8) Defaults to AUTO. Field separator character. Default value is AUTO for autodetection.

  • MERGE_SEPARATOR=[YES/NO]: Defaults to NO. Setting it to YES will enable merging consecutive separators. Mostly useful when it is the space character.

  • AUTODETECT_TYPE=[YES/NO]: Defaults to NO. Setting it to YES will enable auto-detection of field data types. If while reading the records (beyond the records used for autodetection), a value is found to not correspond to the autodetected data type, a warning will be emitted and the field will be emptied.

  • KEEP_SOURCE_COLUMNS=[YES/NO]: Defaults to NO. keep a copy of the original columns where the guessing is active, and the guessed type is different from string. The name of the original columns will be suffixed with "_original". This flag should be used only when ..oo::AUTODETECT_TYPE=YES.

  • AUTODETECT_WIDTH=[YES/NO/STRING_ONLY]: Defaults to NO. Setting it to YES to detect the width of string and integer fields, and the width and precision of real fields. Setting it to STRING_ONLY restricts to string fields. Setting it to NO select default size and width. If while reading the records (beyond the records used for autodetection), a value is found to not correspond to the autodetected width/precision, a warning will be emitted and the field will be emptied.

  • AUTODETECT_SIZE_LIMIT=<bytes>: Defaults to 1000000. size to specify the number of bytes to inspect to determine the data type and width/precision. The default will be 1 000 000. Setting 0 means inspecting the whole file. Note: when reading from standard input, this will be limited to 1 MB, due to how /vsistdin/ is implemented..

  • QUOTED_FIELDS_AS_STRING=[YES/NO]: Defaults to NO. Only used if AUTODETECT_TYPE=YES. Whether to enforce quoted fields as string fields when set to YES. Otherwise, by default, the content of quoted fields will be tested for real, integer, etc... data types.

  • X_POSSIBLE_NAMES=<list_of_names>: Comma separated list of possible names for X/longitude coordinate of a point. Each name might be a pattern using the star character in starting and/or ending position. E.g.: prefix*, *suffix or *middle*. The values in the column must be floating point values. X_POSSIBLE_NAMES and Y_POSSIBLE_NAMES must be both specified and a matching for each must be found in the columns of the CSV file. Only one geometry column per layer might be built when using X_POSSIBLE_NAMES/Y_POSSIBLE_NAMES.

  • Y_POSSIBLE_NAMES=<list_of_names>: Comma separated list of possible names for Y/latitude coordinate of a point. Each name might be a pattern using the star character in starting and/or ending position. E.g.: prefix*, *suffix or *middle*. The values in the column must be floating point values. X_POSSIBLE_NAMES and Y_POSSIBLE_NAMES must be both specified and a matching for each must be found in the columns of the CSV file.

  • Z_POSSIBLE_NAMES=<list_of_names>: Comma separated list of possible names for Z/elevation coordinate of a point. Each name might be a pattern using the star character in starting and/or ending position. E.g.: prefix*, *suffix or *middle*. The values in the column must be floating point values. Only taken into account in combination with X_POSSIBLE_NAMES and Y_POSSIBLE_NAMES.

  • GEOM_POSSIBLE_NAMES=<list_of_names>: Comma separated list of possible names for geometry columns that contain geometry definitions encoded as WKT, WKB (in hexadecimal form, potentially in PostGIS 2.0 extended WKB) or GeoJSON. Each name might be a pattern using the star character in starting and/or ending position. E.g.: prefix*, *suffix or *middle*

  • KEEP_GEOM_COLUMNS=[YES/NO]: Defaults to YES. Expose the detected X,Y,Z or geometry columns as regular attribute fields.

  • HEADERS=[YES/NO/AUTO]: Defaults to AUTO. Whether the first line of the file contains column names or not. When set to AUTO, GDAL will assume the first line is column names if none of the values are strictly numeric.

  • EMPTY_STRING_AS_NULL=[YES/NO]: Defaults to NO. Whether to consider empty strings as null fields on reading'.

  • MAX_LINE_SIZE=<integer>: (GDAL >= 3.5.3) Defaults to 10000000. Maximum number of bytes for a line (-1=unlimited).

Creation Issues

The driver supports creating new databases (as a directory of .csv files), adding new .csv files to an existing directory or .csv files or appending features to an existing .csv table. Starting with GDAL 2.1, deleting or replacing existing features, or adding/modifying/deleting fields is supported, provided the modifications done are small enough to be stored in RAM temporarily before flushing to disk.

Layer Creation options

Layer creation options can be specified in command-line tools using the syntax -lco <NAME>=<VALUE> or by providing the appropriate arguments to GDALDatasetCreateLayer() (C) or Dataset.CreateLayer (Python). The following layer creation options are supported:

  • LINEFORMAT=[CRLF/LF]: By default when creating new .csv files they are created with the line termination conventions of the local platform (CR/LF on win32 or LF on all other systems). This may be overridden through use of the LINEFORMAT layer creation option which may have a value of CRLF (DOS format) or LF (Unix format).

  • GEOMETRY=[AS_WKT/AS_XYZ/AS_XY/AS_YZ]: By default, the geometry of a feature written to a .csv file is discarded. It is possible to export the geometry in its WKT representation by specifying GEOMETRY=AS_WKT. It is also possible to export point geometries into their X,Y,Z components (different columns in the csv file) by specifying GEOMETRY=AS_XYZ, GEOMETRY=AS_XY or GEOMETRY=AS_YX. The geometry column(s) will be prepended to the columns with the attributes values. It is also possible to export geometries in GeoJSON representation using SQLite SQL dialect query, see example below.

  • CREATE_CSVT=[YES/NO]: Defaults to NO. Create the associated .csvt file (see above paragraph) to describe the type of each column of the layer and its optional width and precision.

  • SEPARATOR=[COMMA/SEMICOLON/TAB/SPACE]: Defaults to COMMA. Field separator character.

  • WRITE_BOM=[YES/NO]: Defaults to NO. Write a UTF-8 Byte Order Mark (BOM) at the start of the file.

  • GEOMETRY_NAME=value: Defaults to WKT. Name of geometry column. Only used if GEOMETRY=AS_WKT (and CREATE_CSVT=YES before GDAL 3.7.1).

  • STRING_QUOTING=[IF_NEEDED/IF_AMBIGUOUS/ALWAYS]: Defaults to IF_AMBIGUOUS. whether to double-quote strings. IF_AMBIGUOUS means that string values that look like numbers will be quoted (it also implies IF_NEEDED). Defaults to IF_AMBIGUOUS (behavior in older versions was IF_NEEDED)

Configuration options

Configuration options can be specified in command-line tools using the syntax --config <NAME>=<VALUE> or using functions such as CPLSetConfigOption() (C) or gdal.config_options (Python). The following configuration options are available:

  • OGR_WKT_PRECISION=<integer>: Defaults to 15. Number of decimals for coordinate values. A heuristic is used to remove insignificant trailing 00000x or 99999x that can appear when formatting decimal numbers.

  • OGR_WKT_ROUND=[YES/NO]: Defaults to YES. Whether to enable the above mentioned heuristics to remove insignificant trailing 00000x or 99999x.

Examples

  • This example shows using ogr2ogr to transform a shapefile with point geometry into a .csv file with the X,Y,Z coordinates of the points as first columns in the .csv file

    ogr2ogr -f CSV output.csv input.shp -lco GEOMETRY=AS_XYZ
    
  • This example shows using ogr2ogr to transform a shapefile into a .csv file with geometry field formatted using GeoJSON format.

    ogr2ogr -f CSV output.csv input.shp -dialect sqlite -sql \
        "select AsGeoJSON(geometry) AS geom, * from input"
    
  • Convert a CSV into a GeoPackage. Specify the names of the coordinate columns and assign a coordinate reference system.

    ogr2ogr \
      -f GPKG output.gpkg \
      input.csv \
      -oo X_POSSIBLE_NAMES=longitude \
      -oo Y_POSSIBLE_NAMES=latitude \
      -a_srs 'EPSG:4326'
    
  • Use ogr2ogr -segmentize to densify a input geometry being specified in the WKT special field. Note that one needs to specify the GEOMETRY=AS_WKT layer creation option, otherwise the input geometry would be returned unmodified:

    $ cat input.csv
    WKT,ID,Name
    "LINESTRING (-900 -1450,-900 100)",0,900W
    
    $ ogr2ogr -segmentize 400 -lco GEOMETRY=AS_WKT \
      -sql "SELECT ID, Name FROM input" output.csv input.csv
    
    $ cat output.csv
    WKT,ID,Name
    "LINESTRING (-900 -1450,-900 -1062.5,-900 -675,-900 -287.5,-900 100)","0",900W
    

Particular datasources

The CSV driver can also read files whose structure is close to CSV files :

  • Airport data files NfdcFacilities.xls, NfdcRunways.xls, NfdcRemarks.xls and NfdcSchedules.xls found on that FAA website

  • Files from the USGS GNIS (Geographic Names Information System)

  • The allCountries file from GeoNames

  • Eurostat .TSV files

Other Notes