A nightly report hand-off

A report is generated every night and somebody needs it by morning. Attaching it to an email works until the day it is 40 MB. This recipe sends it as a transfer from cron, logs what went out, and leaves you a record to check against.

The script

#!/usr/bin/env bash
# /usr/local/bin/send-nightly-report
set -euo pipefail

export YUNGLE_API_KEY="$(cat /etc/yungle/api-key)"   # readable by this user only
REPORT="/var/reports/$(date +%F).xlsx"
LOG=/var/log/yungle-reports.jsonl

/usr/local/bin/generate-report > "$REPORT"

yungle send "$REPORT" \
  --to finance@example.com \
  --title "Nightly report $(date +%F)" \
  --expires 7 \
  --json \
  | jq -c --arg file "$REPORT" '{at: now | todate, file: $file, id, url, notified}' \
  >> "$LOG"

And the crontab entry, at six every morning:

0 6 * * * /usr/local/bin/send-nightly-report 2>> /var/log/yungle-reports.err

What each part is for

A key file, not the crontab — cron environments are easy to leak through ps and backups. Give the key only transfers:write and transfers:read.
--expires 7 — a daily report does not need to outlive the week. The value is clamped to your plan’s maximum rather than rejected.
A JSON Lines log— one line per send with the transfer id and link. When someone asks “did Tuesday’s go out?”, the answer is one grep away.
set -euo pipefail — if the report fails to generate, nothing is sent. An empty report delivered on time is worse than a late one.

If the upload is interrupted

Run the same command again. The CLI remembers an interrupted upload of the same files to the same destination and continues it instead of starting over. For a cron job, the next night’s run is a new report and a new transfer, so there is nothing to clean up.

Checking whether the report was opened is a poll against GET /transfers/{id}/downloads using the id from the log — there are no webhooks yet. See Transfers.