Concatenate Multiple CSV Files

Requirement

If you work with macOS, gnu-sed should be installed from Homebrew.

Concatenate into a Single File

Suppose for simplicity that two CSV files file1.csv and file2.csv share the same header as follows:

# file1.csv
column1,column2,column3
foo1,bar1,baz1
foo2,bar2,baz2

# file2.csv
column1,column2,column3
foo3,bar3,baz3

To concatenate those files into a single CSV file, run the following commands

$ awk 'FNR > 1' *.csv > concatenated.csv
$ HEADER=`head -n 1 file1.csv`; gsed -i "1i$HEADER" concatenated.csv

and you will get

# concatenated.csv
column1,column2,column3
foo1,bar1,baz1
foo2,bar2,baz2
foo3,bar3,baz3

as expected.