cron

A cron-expression-based scheduled task tool that runs a shell command at the matching time.

Usage

cron                             - list all jobs
cron add <name> <spec> <cmd>     - add a recurring job
cron oneshot <name> <spec> <cmd> - add a one-shot job
cron remove <name>               - remove a job

Description

• spec is a standard 5-field cron expression; since it contains spaces, quote it: "<minute> <hour> <day> <month> <week>"
• cmd is the shell command to run at the matching time; quote it if it contains spaces
• The timezone is read from the global setting timezone, defaulting to Asia/Shanghai when unset
• Jobs added with add (periodic) run on every match; oneshot jobs are removed automatically after firing once
• The job name must be unique; adding a duplicate name or an invalid expression fails
• Running cron with no arguments lists all jobs, each line showing name, spec, and the type (periodic/oneshot)
• For full expression syntax, see Cron scheduler

Expression fields

Field	Range	Description
Minute	0-59	minute
Hour	0-23	hour
Day	1-31	day of month
Month	1-12 or JAN-DEC	month, name aliases supported
Week	0-6 or SUN-SAT	day of week, 0=Sunday (7 is equivalent to 0)

Each field supports *, n, a-b, */s, a,b,c, etc. When both day and week are explicitly specified, matching either is enough (OR); otherwise both must match (AND).

Examples

# List all jobs
cron

# Run every minute
cron add t1 "* * * * *" "echo hi"

# Run every 5 minutes
cron add t2 "*/5 * * * *" "echo tick"

# Run once at midnight on New Year's Day (one-shot)
cron oneshot newyear "0 0 1 1 *" "echo happy new year"

# Run at 8:30 every Monday
cron add weekly "30 8 * * 1" "echo monday"

# Remove a job
cron remove t1