Each entry in a crontab file consists of six fields, specifying in the following order: minute, hour, day, month, weekday, and command1. Any of these fields can be set to an asterisk (*), which stands for "first through last." So, for example, to run a job every hour, put * in the hour field1. Each entry in a crontab file must end with a newline character (\n), which indicates the end of a line2. A newline character is created by pressing the Enter key on the keyboard. The other options are not valid characters for ending a crontab entry. A tab or a space is used toseparate each field, and a backslash is used to escape special characters or continue a long command to the next line2. References:
* How to Use the Cron Job Format to Schedule Task in Linux
* Syntax of crontab File Entries - Oracle.