Command line relational algebra
csv.exe is a command line tool for performing Relational Algebra on CSV files, written on the .NET platform.
csv [--help] [--in file] command [args...] [command args...]
Reads CSV from StdIn or the --in file and outputs CSV.
Command must be one of the following:
diff[erence] set difference between the input and other file(s)
semijoin|exists rows from input where a matching row exists in other file(s)
intersect set intersection between the input and other file(s)
join natural join of the input and other file(s)
project|select removes columns from the input
rename changes some of the input column names
restrict|where removes rows from the input
union set union between the input and other file(s)
Non-relational commands are:
orderby sorts the input by one or more columns
pretty formats the input CSV in aligned columns
tojson outputs JSON array for the input CSV, one object per row
toxml outputs XML for the input CSV, one element per row
The tools only supports reading CSV at the moment, but will be extened to support reading JSON and XML.
Examples
Join (cat) together multiple CSV files, removing the header lines of all but the first file. All files must have the same set of columns, but column order does not matter. Note that duplicate rows will be removed from the result.
csv < file1.csv union file2.csv file3.csv
Select only the rows from an input file where the service column equals 123
csv < file1.csv restrict service 123
Multiple commands can be combined, for example, combining the first two examples, sorting the result and outputting JSON:
csv < file1.csv UNION file2.csv file3.csv RESTRICT service 123 ORDERBY service TOJSON