The ogrinfo utility

The official documentation for the ogrinfo utility is ​http://www.gdal.org/ogr/ogrinfo.html

-so Summary Only

supress listing of features, show only the summary information like projection, schema, feature count and extents.

To get this info with shapefiles you must also provide the layer name, else not much useful is returned:

$ ogrinfo -so contours.shp

INFO: Open of `contours.shp'
  using driver `ESRI Shapefile' successful.
1: contours (Line String)

Likely what is really wanted is:

$ ogrinfo -so contours.shp contours

INFO: Open of `contours.shp'
      using driver `ESRI Shapefile' successful.

Layer name: contours
Geometry: Line String
Feature Count: 3393
Extent: (57537.995662, 663561.802226) - (88297.082026, 694443.881449)
Layer SRS WKT:
PROJCS["Albers",
...etc.

Alternatively, use the -al switch to see information on all layers.

Adding a column through SQL

Using ogrinfo is it possible to use SQL language to add a column to an input file.

The SQL syntax is a standard ALTER TABLE statement; it's necessary to add -sql switch. In example

$ ogrinfo input.shp -sql "ALTER TABLE input ADD fieldX float"

INFO: Open of `input.shp'
      using driver `ESRI Shapefile' successful.

In ​this zip file there are two files to test this command: an input file ("input.shp") and "input_AfterOgrinfo.shp", that is what "input.shp" becomes after ogrinfo command.