An active line in a crontab will be either an environment setting or a cron command.An environ‐ ment setting is of the form: name = value where the spaces around the equal-sign (=) are optional, and any subsequent non-leading spaces in value will be part of the value assigned to name.The value string may be placed in quotes (single or double, but matching) to preserve leading or trailing blanks.
Special considerations exist when the clock is changed by less than 3 hours, for example at the beginning and end of daylight savings time.
Another note: the LOGNAME variable is sometimes called USER on BSD systems... In addition to LOGNAME, HOME, and SHELL, cron will look at MAILTO if it has any reason to send mail as a result of running commands in "this" crontab.
If MAILTO is defined (and non-empty), mail is sent to the user so named.
If MAILTO is defined but empty (MAILTO=""), no mail will be sent.
Otherwise mail is sent to the owner of the crontab.