Man Pages - Manpage for cron
Posted May 26th, 2004 in Man Pages (Updated June 15th, 2004)
Man page for the unix linux bsd command cron.
NAME
cron - daemon to execute scheduled commands (Vixie Cron)
SYNOPSIS
cron
DESCRIPTION
Cron should be started from /sbin/init.d/cron, /etc/rc or /etc/rc.local. It will return immediately, so you don't need to start it with '&'.
Cron searches /var/spool/cron/tabs for crontab files which are named after accounts in /etc/passwd; crontabs found are loaded into memory. Cron also searches for /etc/crontab which is in a different format (see crontab(5)). Additionally, cron reads the files in /etc/cron.d; it treats the files in /etc/cron.d as extensions to the /etc/crontab file (they follow the special format of that file, i.e. they include the user field). The intended purpose of this feature is to allow packages that require finer control of their scheduling than the /etc/cron.{daily,weekly,monthly} directories allow to add a crontab file to /etc/cron.d. Such files should be named after the package that supplies them. Files must conform to the same naming convention as used by run-parts(8): they must consist solely of upper- and lower-case letters, digits, underscores, and hyphens. Like /etc/crontab, the files in the /etc/cron.d directory are monitored for changes. Cron then wakes up every minute, examining all stored crontabs, checking each command to see if it should be run in the current minute. When executing commands, any output is mailed to the owner of the crontab (or to the user named in the MAILTO environment variable in the crontab, if such exists).
Additionally, cron checks each minute to see if its spool directory's modtime (or the modtime on /etc/crontab) has changed, and if it has, cron will then examine the modtime on all crontabs and reload those which have changed. Thus cron need not be restarted whenever a crontab file is modified. Note that the crontab(1) command updates the modtime of the spool directory whenever it changes a crontab.
SEE ALSO
crontab(1), crontab(5)
AUTHOR
Paul Vixie <paul@vix.com>
This manual page was generated by The Electric Toolbox using SuSE Linux Professional 9.0
Subscribe!
If you found this post interesting and would like to be notified the next time something is posted, please subscribe to my RSS Feed. Thanks for visiting!
RSS Feed