systab/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Overview

systab is a single-file Bash script that provides a cron/at/batch-like interface for systemd user timers. It creates, manages, and cleans up systemd .service and .timer unit files in ~/.config/systemd/user/. Managed units are tagged with a # SYSTAB_MANAGED marker comment. Unit filenames use a 6-char hex ID (e.g., systab_a1b2c3.timer) which doubles as the human-facing job identifier.

Running

./systab [OPTIONS]

No build step. The script requires bash, systemctl, and optionally notify-send (for -i) and sendmail/msmtp (for -m).

Architecture

The script has two modes controlled by CLI flags:

• Job creation (-t <time> [-c <cmd> | -f <script> | stdin]): Generates a systemd .service + .timer pair with a 6-char hex short ID, reloads the daemon, and enables/starts the timer. Time specs are parsed via parse_time which handles natural language (every 5 minutes), date -d relative/absolute times, and raw systemd OnCalendar values. One-time jobs get Persistent=false and RemainAfterElapse=no (auto-unload after firing). All jobs log stdout/stderr to the journal via SyslogIdentifier. Notifications (-i desktop, -m email, -o include output) use ExecStopPost so they fire on both success and failure with status-aware icons/messages. The -o [N] flag fetches the last N lines of journal output (default 10) and includes them in the notification body (also configurable in edit mode as o or o=N). Notification flags are persisted in the service file as a # SYSTAB_FLAGS= comment.

• Management (-P, -R, -E, -L, -S, -C, -h — mutually exclusive):

  • -P <id> / -R <id>: Pause (stop+disable) or resume (enable+start) a job's timer.
  • -E: Opens $EDITOR with a pipe-separated crontab (ID[:FLAGS] | SCHEDULE | COMMAND). Notification flags are appended to the ID with : (i = desktop, e=addr = email, o = output 10 lines, o=N = output N lines, comma-separated). On save, diffs against the original to apply creates (ID=new), deletes (removed lines), updates (changed schedule/command/flags), and pause/resume (comment/uncomment lines).
  • -L [id] [filter]: Query journalctl logs for managed jobs (both unit messages and command output). Optional job ID to filter to a single job.
  • -S [id]: Show timer status via systemctl, including short IDs and disabled state. Optional job ID to show a single job.
  • -C: Interactively clean up elapsed one-time timers (removes unit files from disk).

Key functions: parse_time (time spec → OnCalendar), _write_unit_files (shared service+timer creation), create_job/create_job_from_edit (thin wrappers), edit_jobs (crontab-style edit with diff-and-apply), get_managed_units (find tagged units by type), clean_jobs (remove elapsed one-time timers), pause_job/resume_job (disable/enable timers), write_notify_lines (append ExecStopPost notification lines), build_flags_string/parse_flags (convert between CLI options and flags format).

Testing

There are no automated tests. Test manually with systemd user timers:

./systab -t "every 5 minutes" -c "echo test"
./systab -S
./systab -L
./systab -P <id>
./systab -R <id>
./systab -C

Notes

• ShellCheck can be used for linting: shellcheck systab.
• Edit mode uses | as the field delimiter (not tabs or spaces) to allow multi-word schedules. Notification flags use : after the ID (e.g., a1b2c3:i,o,e=user@host).
• Notification flags (i = desktop, o/o=N = include output, e=addr = email) are persisted as # SYSTAB_FLAGS=... comments in service files and as ExecStopPost= lines using $SERVICE_RESULT/$EXIT_STATUS for status-aware messages. Unit file printf format strings must use %%s (not %s) since systemd expands %s as a specifier before the shell runs.
• Journal logs are queried with USER_UNIT OR SYSLOG_IDENTIFIER to capture both systemd messages and command output.