Parse CSV attachments from Gmail into Google Sheets.

// importGmailCsv.gs — search Gmail, parse first CSV attachment, append to Sheet
function importGmailCsv() {
  var QUERY = 'subject:"weekly export" has:attachment newer_than:7d';
  var SHEET_ID = 'YOUR_SPREADSHEET_ID';
  var SHEET_NAME = 'Imports';
  var CHARSET = 'windows-1252';

  var threads = GmailApp.search(QUERY, 0, 10);
  var sheet = SpreadsheetApp.openById(SHEET_ID).getSheetByName(SHEET_NAME);

  for (var t = 0; t < threads.length; t++) {
    var messages = threads[t].getMessages();
    for (var m = 0; m < messages.length; m++) {
      var attachments = messages[m].getAttachments();
      for (var a = 0; a < attachments.length; a++) {
        var att = attachments[a];
        if (att.getName().slice(-4).toLowerCase() !== '.csv') continue;
        var csv = att.getDataAsString(CHARSET);
        var rows = Utilities.parseCsv(csv);
        sheet.getRange(sheet.getLastRow() + 1, 1, rows.length, rows[0].length)
             .setValues(rows);
      }
    }
  }
}

Need a variant? Gnaw writes a custom version from one sentence — fields, triggers, edge cases handled.

Walkthrough

Review original identifiers before importing

Leading zeros and long digit strings deserve a check against the original attachment before import. Paste one original identifier per line into the free browser check. It flags possible conversion risks; it cannot recover digits or zeros that have already been lost. Do not paste a whole CSV file into the identifier checker.

Match incoming columns to your expected headers

Compare one expected header record with the incoming file’s header. See which names moved, are missing or are unexpected before connecting columns in a script. Names match exactly, including case and spaces; the check never guesses or rearranges your data.

Comparing two pasted tab-separated tables? Preview changed cells and added or removed IDs using an explicit key column, before deciding what to update.

Need rows to become columns? Preview a literal transpose of a pasted tab-separated table, including its header.

Check empty required cells in a literal tab-separated table by choosing column numbers yourself. This does not infer business rules or edit a Sheet.

Need this check in a local script? Download the same required-field checker with a runnable example. Select required columns yourself; the module does not infer business rules.

Repeated complete rows? Review exact matches and their original positions before deciding what to keep. Every row, including any header, is checked; nothing is deleted.

Preview quoted CSV before importing

Choose the delimiter and preview raw CSV records, including quoted commas, doubled quotes and embedded newlines. The free check keeps values as text and shows original line references, blank or repeated headers and uneven field counts. It does not import data, run formulas or certify a safe import.

Check the parsed table before writing it

After parsing the CSV, review a literal tab-separated table for uneven rows, missing headers and formula-like prefixes. These checks do not parse raw CSV: commas, quoted tabs and multiline cells need your CSV parser first. The prefix review can flag intentional formulas or negative numbers and does not certify safe imports. Nothing is imported or changed.

My CSV has a header row and I don't want it repeated in the sheet on every run. How do I skip it?

Slice the rows array before writing: pass rows.slice(1) to setValues instead of rows. If you also need to write the header once when the sheet is empty, check sheet.getLastRow() === 0 and write rows[0] separately on the first run.

Utilities.parseCsv throws 'Cannot call method parseCsv of undefined'. What is wrong?

This happens when the attachment's getDataAsString returns an empty string, usually because the charset argument is wrong and the decode failed silently in older Apps Script runtimes. Log att.getBytes().length before calling getDataAsString to confirm the attachment has content, then verify the charset. On newer runtimes, a bad charset will throw a more descriptive error instead.

The script times out when there are many messages. What is the limit?

Apps Script imposes a 6-minute execution ceiling on triggered functions and 30 seconds on manually run functions. If you are processing large batches, break the work across runs: write the last processed thread index to PropertiesService (PropertiesService.getScriptProperties().setProperty('lastIndex', t)), read it at the start of the next run, and pick up from there. This is sometimes called a continuation pattern.

Can I run this on a schedule without opening the spreadsheet manually?

Yes. In the Apps Script editor go to Triggers (clock icon on the left sidebar), add a time-driven trigger pointing at importGmailCsv, and set the interval. Hourly or daily is typical for email exports. The trigger runs under your account so it inherits your Gmail and Sheets permissions — no extra OAuth setup needed beyond the initial manual authorization run.

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