The -t, flag sets the field delimiter to a comma, which is how datamash reads CSV (comma-separated values) files. Summing column 4 then produces one number for the whole file, and --header-in keeps the header row out of the math. Use this one-liner instead of awk when you want a quick total of a numeric column. Add -g for per-group totals, as in the grouped examples in this catalog.
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