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 mail (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.
Management (-P, -R, -E, -L, -S, -C — 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 | SCHEDULE | COMMAND). On save, diffs against the original to apply creates (ID=new), deletes (removed lines), updates (changed schedule/command), and pause/resume (comment/uncomment lines).
- -L [filter]: Query journalctl logs for managed jobs (both unit messages and command output).
- -S: Show timer status via systemctl, including short IDs and disabled state.
- -C: Interactively clean up elapsed one-time timers (removes unit files from disk).

Key functions: parse_time (time spec → OnCalendar), create_job (generates unit files), edit_jobs (crontab-style edit with diff-and-apply), get_managed_services/get_managed_timers (find tagged units), clean_jobs (remove elapsed one-time timers), pause_job/resume_job (disable/enable timers).

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.
Journal logs are queried with USER_UNIT OR SYSLOG_IDENTIFIER to capture both systemd messages and command output.

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