icsevent - sleep(1) using ICS calendar events

SYNOPSIS

icsevent [options] URL

DESCRIPTION

icsevent is a simple, minimal command line utility for polling ICS files for calendar events. icsevent runs as part of a shell pipeline to send notifications or kick off other jobs.

The ICS format is parsed using gocal.

By default, events are converted to a percent-encoded, line oriented format that can be piped to other utilities.

Using the --wait option will cause icsevent to sleep until the next event.

BUILDING

go install github.com/msantos/icsevent@latest

To build a reproducible executable from the git repository:

CGO_ENABLED=0 go build -trimpath -ldflags "-w"

POLLING

When the --wait option is used, some options can be used to control the polling interval. icsevent should be run under a supervisor process like daemontools.

--wait-max=15m

The --wait-max option controls how long icsevent will sleep before polling for new events.

For example, if the next event happens in 1 month, icsevent will:
- exit after 15 minutes
- be restarted by the supervisor process
- poll for events
--wait-min=30m

The --wait-min option controls the polling rate when no events are found.

If no events are found, icsevent will exit immediately by default and be restarted by the supervisor, polling the calendar service every second.

Setting the value of the --wait-min option to "30m" limits the rate of polling to 1 connection every 30 minutes.

EXAMPLES

Dump events for the next 3 months

icsevent --duration="$((3*30*24))h" https://www.calendarlabs.com/ical-calendar/ics/39/Canada_Holidays.ics

Modify formatting

FORMAT='{{if eq .State "start"}}
{{- .Date}}

{{.Summary}}
{{- if .Location }}
Location: {{.Location}}
{{- end }}
{{- if .Description}}
Description: {{.Description}}
{{- end }}
{{else}}
---
{{end}}'

icsevent --duration="$((3*30*24))h" \
  --output-format="$FORMAT" \
  https://www.calendarlabs.com/ical-calendar/ics/39/Canada_Holidays.ics

Wait for next event

icsevent --wait --duration="$((3*30*24))h" \
  --output-format="$FORMAT" \
  https://www.calendarlabs.com/ical-calendar/ics/39/Canada_Holidays.ics

Wait with poll intervals

icsevent --wait --wait-max=60m --wait-min=30m --duration="$((3*30*24))h" \
  https://www.calendarlabs.com/ical-calendar/ics/39/Canada_Holidays.ics

daemontools: run scripts: sending to an XMPP groupchat

Uses xmppipe.

To run:

svscan service

service/20-icsevent/run

#!/bin/sh

URL="https://www.calendarlabs.com/ical-calendar/ics/39/Canada_Holidays.ics"

NOTIFYDIR="$TMPDIR/xmpp-notify"

# Use XEP-0393: Message Styling
FORMAT='{{.Date}}: {{.State}}: *{{.Summary}}*
{{- if .Location }}
_Location_: {{.Location}}
{{- end }}
{{- if .Description}}
_Description_: {{.Description}}
{{- end }}
{{- if .Attendees}}
_Attendees_:
{{ range .Attendees }}* {{ if .Cn }}{{.Cn}}{{else}}{{ .Value}}{{end}}
{{ end }}
{{- end }}
{{- if .Organizer}}
_Organizer_: {{.Organizer.Cn}}
{{- end }}
'

exec > "$NOTIFYDIR/pipe" 2>&1
exec icsevent \
    --output-format="$FORMAT" \
    --wait \
    --wait-min=900 \
    --wait-max=901 \
    --duration=24h \
    "$URL"

service/10-xmppipe/run

#!/bin/sh

umask 0077

NOTIFYDIR="$TMPDIR/xmpp-notify"

export XMPPIPE_USERNAME="bot@example.com"
export XMPPIPE_PASSWORD="bot-password"

mkdir -p "$NOTIFYDIR"
rm -f "$NOTIFYDIR/pipe"
mkfifo "$NOTIFYDIR/pipe"
exec <> "$NOTIFYDIR/pipe"
exec xmppipe -o groupchat

OPTIONS

--dryrun : When running with --wait, do not actually sleep

--duration duration : Window beginning at start time to check for events (default 15m0s)

--output-format string : Template for formatting output using the Go template syntax

--start int : Start time in epoch seconds (default: now)

--verbose int : Enable debug messages

--wait : Wait for first event

--wait-max int : Maximum time to wait for next event

--wait-min int : Minimum amount of time to poll for new events

TEMPLATE FUNCTIONS

text

Converts HTML to styled plain text.

{{.Description | text}}

match

Boolean regular expression match:

{{- if not (match "(?i)^Cancelled" .Summary) -}}
...
{{ end }}

msantos / icsevent