Cron Syntax

Cron will schedule a command to be executed at a specific time. Cron expects five time parameters, and a valid command.

The times are correlated with:

  • minute: 0-59
  • hour: 0-23
  • Day of Month: 1-31
  • Month of Year: 0-11
  • Day of Week: 1-7

After the five time parameters are provided to Cron, it expects a valid command resulting in the line:

* * * * * echo "Hello Cron" >> ~/Desktop/hello-cron.log

The above cronjob would run and append the phrase “Hello Cron” to the hello-cron.log file every minute.


In the preceding example the five time parameters are each * indicating to run at every minute, hour, day of the month, month of the year, and day of the week.

Cron will execute the command echo "Hello Cron" >> ~/Desktop/hello-cron.log every minute of every hour of every day of the month of every day of the year of every day of the week.

Special Characters

  • * Asterisk: Specifies that the command will fire at every interval in a given time slot
  • - Hyphen: Expression to designate a range of values within a given time slot
  • / Forward Slash: Expression to allow dividing time slot into intervals
  • , Comma: Expression to create a list within any given time slot