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diff --git a/crontab.5 b/crontab.5 new file mode 100644 index 0000000..01b52f0 --- /dev/null +++ b/crontab.5 @@ -0,0 +1,188 @@ +.\"/* Copyright 1988,1990,1993,1994 by Paul Vixie +.\" * All rights reserved +.\" * +.\" * Distribute freely, except: don't remove my name from the source or +.\" * documentation (don't take credit for my work), mark your changes (don't +.\" * get me blamed for your possible bugs), don't alter or remove this +.\" * notice. May be sold if buildable source is provided to buyer. No +.\" * warrantee of any kind, express or implied, is included with this +.\" * software; use at your own risk, responsibility for damages (if any) to +.\" * anyone resulting from the use of this software rests entirely with the +.\" * user. +.\" * +.\" * Send bug reports, bug fixes, enhancements, requests, flames, etc., and +.\" * I'll try to keep a version up to date. I can be reached as follows: +.\" * Paul Vixie <paul@vix.com> uunet!decwrl!vixie!paul +.\" */ +.\" +.\" $Id: crontab.5,v 2.4 1994/01/15 20:43:43 vixie Exp $ +.\" +.TH CRONTAB 5 "24 January 1994" +.UC 4 +.SH NAME +crontab \- tables for driving cron +.SH DESCRIPTION +A +.I crontab +file contains instructions to the +.IR cron (8) +daemon of the general form: ``run this command at this time on this date''. +Each user has their own crontab, and commands in any given crontab will be +executed as the user who owns the crontab. Uucp and News will usually have +their own crontabs, eliminating the need for explicitly running +.IR su (1) +as part of a cron command. +.PP +Blank lines and leading spaces and tabs are ignored. Lines whose first +non-space character is a pound-sign (#) are comments, and are ignored. +Note that comments are not allowed on the same line as cron commands, since +they will be taken to be part of the command. Similarly, comments are not +allowed on the same line as environment variable settings. +.PP +An active line in a crontab will be either an environment setting or a cron +command. An environment setting is of the form, +.PP + name = value +.PP +where the spaces around the equal-sign (=) are optional, and any subsequent +non-leading spaces in +.I value +will be part of the value assigned to +.IR name . +The +.I value +string may be placed in quotes (single or double, but matching) to preserve +leading or trailing blanks. +.PP +Several environment variables are set up +automatically by the +.IR cron (8) +daemon. +SHELL is set to /bin/sh, and LOGNAME and HOME are set from the /etc/passwd +line of the crontab's owner. +HOME and SHELL may be overridden by settings in the crontab; LOGNAME may not. +.PP +(Another note: the LOGNAME variable is sometimes called USER on BSD systems... +on these systems, USER will be set also.) +.PP +In addition to LOGNAME, HOME, and SHELL, +.IR cron (8) +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. This +option is useful if you decide on /bin/mail instead of /usr/lib/sendmail as +your mailer when you install cron -- /bin/mail doesn't do aliasing, and UUCP +usually doesn't read its mail. +.PP +The format of a cron command is very much the V7 standard, with a number of +upward-compatible extensions. Each line has five time and date fields, +followed by a user name if this is the system crontab file, +followed by a command. Commands are executed by +.IR cron (8) +when the minute, hour, and month of year fields match the current time, +.I and +when at least one of the two day fields (day of month, or day of week) +match the current time (see ``Note'' below). +.IR cron (8) +examines cron entries once every minute. +The time and date fields are: +.IP +.ta 1.5i +field allowed values +.br +----- -------------- +.br +minute 0-59 +.br +hour 0-23 +.br +day of month 0-31 +.br +month 0-12 (or names, see below) +.br +day of week 0-7 (0 or 7 is Sun, or use names) +.br +.PP +A field may be an asterisk (*), which always stands for ``first\-last''. +.PP +Ranges of numbers are allowed. Ranges are two numbers separated +with a hyphen. The specified range is inclusive. For example, +8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10 +and 11. +.PP +Lists are allowed. A list is a set of numbers (or ranges) +separated by commas. Examples: ``1,2,5,9'', ``0-4,8-12''. +.PP +Step values can be used in conjunction with ranges. Following +a range with ``/<number>'' specifies skips of the number's value +through the range. For example, ``0-23/2'' can be used in the hours +field to specify command execution every other hour (the alternative +in the V7 standard is ``0,2,4,6,8,10,12,14,16,18,20,22''). Steps are +also permitted after an asterisk, so if you want to say ``every two +hours'', just use ``*/2''. +.PP +Names can also be used for the ``month'' and ``day of week'' +fields. Use the first three letters of the particular +day or month (case doesn't matter). Ranges or +lists of names are not allowed. +.PP +The ``sixth'' field (the rest of the line) specifies the command to be +run. +The entire command portion of the line, up to a newline or % +character, will be executed by /bin/sh or by the shell +specified in the SHELL variable of the cronfile. +Percent-signs (%) in the command, unless escaped with backslash +(\\), will be changed into newline characters, and all data +after the first % will be sent to the command as standard +input. +.PP +Note: The day of a command's execution can be specified by two +fields \(em day of month, and day of week. If both fields are +restricted (ie, aren't *), the command will be run when +.I either +field matches the current time. For example, +.br +``30 4 1,15 * 5'' +would cause a command to be run at 4:30 am on the 1st and 15th of each +month, plus every Friday. +.SH EXAMPLE CRON FILE +.nf + +# use /bin/sh to run commands, no matter what /etc/passwd says +SHELL=/bin/sh +# mail any output to `paul', no matter whose crontab this is +MAILTO=paul +# +# run five minutes after midnight, every day +5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 +# run at 2:15pm on the first of every month -- output mailed to paul +15 14 1 * * $HOME/bin/monthly +# run at 10 pm on weekdays, annoy Joe +0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?% +23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" +5 4 * * sun echo "run at 5 after 4 every sunday" +.fi +.SH SEE ALSO +cron(8), crontab(1) +.SH EXTENSIONS +When specifying day of week, both day 0 and day 7 will be considered Sunday. +BSD and ATT seem to disagree about this. +.PP +Lists and ranges are allowed to co-exist in the same field. "1-3,7-9" would +be rejected by ATT or BSD cron -- they want to see "1-3" or "7,8,9" ONLY. +.PP +Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". +.PP +Names of months or days of the week can be specified by name. +.PP +Environment variables can be set in the crontab. In BSD or ATT, the +environment handed to child processes is basically the one from /etc/rc. +.PP +Command output is mailed to the crontab owner (BSD can't do this), can be +mailed to a person other than the crontab owner (SysV can't do this), or the +feature can be turned off and no mail will be sent at all (SysV can't do this +either). +.SH AUTHOR +.nf +Paul Vixie <paul@vix.com> |