A simple utility library and scripts to perform simple operations on CSV files. At the moment, the following operations are supported:

• Selecting specific columns (by index)
• Filter rows, based on a specific field
• Join two CSV files on a single column
• Enumerate the CSV headers (convenient for CSV files with many columns)

gem install csv_tools

Using the following data files

$ cat students.csv
student-id,name
1,Alice
2,Bob
3,Rob
4,Allie

$ cat marks.csv
student-id,Assignment 1,Assignment 2,Test
1,72,83,77
2,53,61,58
3,85,88,87
4,92,80,75

Select specific columns, by index.

$ csv_select marks.csv 0 3
student-id,Test
1,77
2,58
3,87
4,75

Join two files on a column (called student-id)

$ csv_join students.csv marks.csv student-id
student-id,name,Assignment 1,Assignment 2,Test
1,Alice,72,83,77
2,Bob,53,61,58
3,Rob,85,88,87
4,Allie,92,80,75

Keep rows whose second column (i.e. at index 1) contains the string ob

$ csv_join students.csv marks.csv student-id > joined.csv

$ csv_filter joined.csv 1 ob
student-id,name,Assignment 1,Assignment 2,Test
2,Bob,53,61,58
3,Rob,85,88,87

When working with CSV that have many columns, it is convenient to be able to enumerate the column-headers.

$ csv_enum marks.csv
0	: student-id
1	: Assignment 1
2	: Assignment 2
3	: Test