usage: csvstack [-h] [-d DELIMITER] [-t] [-q QUOTECHAR] [-u {0,1,2,3}] [-b]
                [-p ESCAPECHAR] [-z FIELD_SIZE_LIMIT] [-e ENCODING] [-S] [-H]
                [-K SKIP_LINES] [-v] [-l] [--zero] [-V] [-g GROUPS]
                [-n GROUP_NAME] [--filenames]
                [FILE [FILE ...]]
Stack up the rows from multiple CSV files, optionally adding a grouping value.
positional arguments:
  FILE                  The CSV file(s) to operate on. If omitted, will accept
                        input as piped data via STDIN.
optional arguments:
  -h, --help            show this help message and exit
  -g GROUPS, --groups GROUPS
                        A comma-separated list of values to add as "grouping
                        factors", one for each CSV being stacked. These are
                        added to the output as a new column. You may specify a
                        name for the new column using the -n flag.
  -n GROUP_NAME, --group-name GROUP_NAME
                        A name for the grouping column, e.g. "year". Only used
                        when also specifying -g.
  --filenames           Use the filename of each input file as its grouping
                        value. When specified, -g will be ignored.

If you redirect output to an input file like csvstack file.csv > file.csv, the file will grow indefinitely.

csvstack -g 2009,2010 examples/realdata/FY09_EDU_Recipients_by_State.csv examples/realdata/Datagov_FY10_EDU_recp_by_State.csv

csvstack -n NEWCOL -g "" examples/dummy.csv