added help on the cron utility

reference/static/commands/osx/cron.md

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+# cron
+-------------
+## INFO
+
+cron is a daemon or process which runs in the background.
+
+## DETAILS
+
+Specifically, it allows the user to schedule predefined processes to run in the background at a regular interval of time.
+
+cron repeatedly checks for when the scheduled time matches the current time, and then executes its task once that condition is met.
+
+## SYNTAX
+
+cron [-f] [-l] [-n] [-L loglevel]
+
+### Modifications
+
+-f keeps the process in the foreground
+
+-l enables LSB compliant names for cron.d files
+
+-n adds the Fully Qualified Domain Name(FQDN) in the subject when sending email
+
+-L loglevel tells cron what to log with the following modifications
+
+-L 1 logs the start of all cron jobs
+
+-L 2 logs the end of all cron jobs
+
+-L 4 logs all the failed jobs. The exit status will be non-zero
+
+-L 8 logs the process number of all the cron jobs