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Vixie Cron

The reference implementation of {{Unix cron}} written by Paul Vixie in 1987 and the basis of nearly every modern Linux and BSD cron daemon.

Vixie cron is the descendant of Paul Vixie's 1987 rewrite of the original Unix cron daemon. After canvassing Unix users for feature requests, Vixie released a version that fixed long-standing reliability problems with earlier crons and expanded the crontab grammar. Version 3 followed in late 1993 and effectively became the de-facto standard. Vixie cron introduced or popularised the conveniences most users now take for granted: per-user crontabs editable via `crontab -e`, the `/etc/cron.d/` drop-in directory, case-insensitive month and weekday names (JAN-DEC, SUN-SAT), step values like `*/5`, and the `@`-prefixed nicknames (`@hourly`, `@daily`, `@weekly`, `@monthly`, `@yearly`, `@annually`, `@midnight`, and the special `@reboot` that fires once when the daemon starts). It also locked in the controversial OR semantics for the day-of-month and day-of-week fields when both are restricted, a behaviour inherited from the original cron and now codified in Cron Expressions and Common Pitfalls. Most current Linux distributions ship a fork rather than upstream Vixie cron itself. Cronie (used by Fedora, RHEL, Arch) and Debian cron are the two dominant lines, each adding security hardening, SELinux integration, PAM support, and patched Daylight Saving Time handling. Vixie cron's syntax and semantics, however, remain the lingua franca that downstream forks and many third-party schedulers aim to imitate.

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Confidence

93%

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Created

June 05, 2026

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