Efficiently concatenate CSVs (or other tabular text files), stripping extra header lines. So far, is the fastest non-compiled script I've been able to devise. Plenty open to improvements and suggestions.
Should work on Linux and OSX. Please file an issue if not.
./csvcat.sh file1 file2 [...] > concatenated.csv
csvcat prints the entirety of file1, plus all but the first lines of the remaining files, to stdout. In the command above, this output is redirected to a new file, concatenated.csv.
Not necessary, but provides easier access to the tool:
cp csvcat.sh /usr/local/bin/csvcat
... after which you can run the following command from any directory:
csvcat file1 file2 [...] > concatenated.csv