merge-csv-on-column

A CLI utility for merging multiple CSV files on a column

Quick start

1. From the project root, install dependencies:

   npm ci

2. Run the script:

   node ./merge-csv-on-column.js "./source_csv/Users.csv" "./source_csv/Users Access.csv"

   Interactive mode (checkbox selection):

   node ./merge-csv-on-column.js --interactive "./source_csv/Users.csv" "./source_csv/Users Access.csv"

Run with npx (no install)

You can run the CLI without installing it globally using npx:

npx merge-csv-on-column "./source_csv/Users.csv" "./source_csv/Users Access.csv"

Interactive mode via npx:

npx merge-csv-on-column --interactive "./source_csv/Users.csv" "./source_csv/Users Access.csv"

Note: The first time you run npx, it may prompt to install the package. Use npx --yes merge-csv-on-column ... for non-interactive environments.

Options

• -o, --output <path> — output CSV path (default: ./merged.csv)
• --conflict <first|last> — conflict resolution when multiple files provide values for the same column (default: first)
• --preview — print the first 10 rows of the merged output
• --interactive — choose columns interactively with a checkbox UI (falls back to textual prompt)
• --columns "A,B,C" — non-interactive comma-separated columns list
• -k, --key <field> — column to merge on (default: Email). In interactive mode, you can also choose the key from detected headers.

Example: specify exact columns to keep (non-interactive)

The following example keeps only these columns in the output:

node ./merge-csv-on-column.js --columns "Email, First name, Last name, Accepted site invitation, Description, Invited on, Accepted the invitation, Account verified, Logged in, Issued at least a command" "./source_csv/Users.csv" "./source_csv/Users Access.csv"

Notes

• The script requires at least two input CSV files and defaults to using an Email column as the merge key.
• Paths with spaces should be quoted.

License

MIT