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Qasim Muhammad
Qasim Muhammad

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Build a daily email digest with cron and 6 lines of bash

#bash #linux #productivity #automation

Every product team rebuilds the same thing: a 7 AM email summarising what happened yesterday. Signups. Errors. New customers. Pipeline counts. Some teams use Looker. Some pay Zapier. Some have a sheet that nobody opens.

The honest answer for most cases: 6 lines of bash, one cron entry, ship.

What you need

  • A Linux box (or macOS) with cron
  • Whatever query speaks to your data (psql, mysql, an API)
  • The Nylas CLI installed and authenticated 
brew install nylas/nylas-cli/nylas
# or: curl -fsSL https://cli.nylas.com/install.sh | bash
nylas auth config --api-key YOUR_KEY
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The script

Save as /opt/scripts/digest.sh:

#!/usr/bin/env bash
set -euo pipefail

SIGNUPS=$(psql -tA -h db.example.com -U readonly app -c "SELECT count(*) FROM users WHERE created_at > now() - interval '1 day'")
ERRORS=$(psql -tA -h db.example.com -U readonly app -c "SELECT count(*) FROM events WHERE level='error' AND created_at > now() - interval '1 day'")
REVENUE=$(psql -tA -h db.example.com -U readonly app -c "SELECT coalesce(sum(amount_cents), 0)/100 FROM payments WHERE created_at > now() - interval '1 day'")

nylas email send --to team@yourapp.com \
  --subject "Daily digest $(date +%F)" \
  --body "Signups: $SIGNUPS\nErrors: $ERRORS\nRevenue: \$$REVENUE"
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That is it. Six lines if you count the shebang and the set directive.

The cron entry 

# /etc/cron.d/digest
0 7 * * 1-5 ops bash /opt/scripts/digest.sh
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7 AM, Monday through Friday, run as the ops user. Logs to syslog by default — journalctl -u cron to inspect.

Why this beats the alternatives

Alternative Cost Flex
Looker / Metabase scheduled email $50+/seat/mo Drag-drop dashboards, no script
Zapier scheduled task $0.024 per run = $0.50/mo per digest Visual editor, vendor lock
Internal "ReportingService" 4 weeks of eng time Future-proof
This script Whatever Postgres + email cost Total

For 90% of "email me yesterday's numbers" requests, the script wins. The other 10% need charts, drill-down, or non-engineering authoring — that is when Looker pays back.

Make it nicer

HTML body for charts 

nylas email send --to team@yourapp.com \
  --subject "Daily digest $(date +%F)" \
  --html "<h1>Daily digest</h1><table><tr><th>Metric</th><th>Value</th></tr><tr><td>Signups</td><td>$SIGNUPS</td></tr></table>"
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Sparklines from the last 7 days 

SPARK=$(psql -tA -c "SELECT array_agg(c) FROM (SELECT count(*) c FROM users WHERE created_at > now() - interval '7 days' GROUP BY date_trunc('day', created_at) ORDER BY 1) t" | sed 's/[{}]//g')
# Render with https://github.com/holman/spark
SPARK_LINE=$(echo $SPARK | tr ',' ' ' | spark)
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Attachment with the raw CSV 

psql -c "\copy (SELECT * FROM yesterday_summary) TO '/tmp/digest.csv' CSV HEADER"
nylas email send --to team@yourapp.com \
  --subject "Daily digest $(date +%F)" \
  --body "Numbers attached." \
  --attachment /tmp/digest.csv
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Skip weekends or holidays 

# At top of digest.sh:
HOLIDAYS_FILE=/opt/scripts/us-holidays.txt
TODAY=$(date +%F)
if grep -qx "$TODAY" "$HOLIDAYS_FILE"; then
  exit 0
fi
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A common gotcha

Cron runs with a minimal PATH. If nylas is in ~/.config/nylas/bin (the default install location), either symlink it to /usr/local/bin/nylas or set PATH at the top of your script:

export PATH="$HOME/.config/nylas/bin:$PATH"
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If your job runs as a different user (e.g., ops), the install needs to be visible to that user.

Going further

  • Per-team digests: loop over a list of recipients with for team in eng product sales; do nylas email send ...; done
  • On-call alerts: combine with a service that emits errors to a queue, send only when count > threshold
  • Daily metrics from Coralogix / Datadog: replace psql with the provider's CLI or curl to their API

Six lines is the floor, not the ceiling. Most teams stay near the floor for years.

Next steps

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