From: Georges Khaznadar Date: Wed, 11 Oct 2023 11:43:22 +0200 Subject: crontab_5_manpage MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Fixed the phrasing of the manual page, tanks to Reuben Thomas, and included 積丹尼 Dan Jacobson's nice example into crontab.5 --- crontab.5 | 114 ++++++++++++++++++++------------------------------------------ 1 file changed, 36 insertions(+), 78 deletions(-) diff --git a/crontab.5 b/crontab.5 index 260fee9..a49d89f 100644 --- a/crontab.5 +++ b/crontab.5 @@ -33,20 +33,15 @@ 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 hash-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. +Note that comments on the same line as cron commands are not interpreted as +comments in the cron sense, but are considered part of the command and passed +to the shell. This is similarly true for comments 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. The crontab file is parsed from top to bottom, so any environment -settings will affect only the cron commands below them in the file. -An environment setting is of the form, +command. An environment setting is of the form, .PP -.in +4n -name = value -.in + name = value .PP where the spaces around the equal-sign (=) are optional, and any subsequent non-leading spaces in @@ -91,53 +86,21 @@ 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. PATH is set to "/usr/bin:/bin". -HOME, SHELL, and PATH may be overridden by settings in the crontab; -LOGNAME is the user that the job is running from, and may not be changed. +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 and MAILFROM if it has any reason to send mail as a result -of running commands in ``this'' crontab. -.PP -If MAILTO is defined (and non-empty), mail is sent to the user so named. -MAILTO may also be used to direct mail to multiple recipients by separating -recipient users with a comma. If MAILTO is defined but empty (MAILTO=""), -no mail will be sent. Otherwise mail is sent to the owner of the crontab. -.PP -If MAILFROM is defined, the sender email address is set to MAILFROM. Otherwise -mail is sent as "root (Cron Daemon)". -.PP -On the Debian GNU/Linux system, cron supports the -.B pam_env -module, and loads the environment specified by -.I /etc/environment -and -.IR /etc/security/pam_env.conf . -It also reads locale information from -.IR /etc/default/locale . -However, the PAM settings do -.B NOT -override the settings described above nor any settings in the -.I crontab -file itself. Note in particular that if you want a PATH other than -"/usr/bin:/bin", you will need to set it in the crontab file. -.PP -By default, cron will send mail using the mail "Content-Type:" header of -"text/plain" with the "charset=" parameter set to the charmap / codeset of the -locale in which -.IR crond (8) -is started up \(en i.e.\& either the default system locale, -if no LC_* environment variables are set, or the locale specified by -the LC_* environment variables -( see -.IR locale (7) ). -You can use different character encodings for mailed cron job output by -setting the CONTENT_TYPE and CONTENT_TRANSFER_ENCODING variables in crontabs, -to the correct values of the mail headers of those names. +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, @@ -163,30 +126,30 @@ field allowed values .br ----- -------------- .br -minute 0\(en59 +minute 0-59 .br -hour 0\(en23 +hour 0-23 .br -day of month 1\(en31 +day of month 0-31 .br -month 1\(en12 (or names, see below) +month 0-12 (or names, see below) .br -day of week 0\(en7 (0 or 7 is Sun, or use names) +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 +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''. +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 ``/'' specifies skips of the number's value -through the range. For example, ``0\-23/2'' can be used in the hours +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 @@ -201,16 +164,15 @@ 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 crontab file. +specified in the SHELL variable of the cronfile. Percent-signs (%) in the command, unless escaped with backslash -(\e), will be changed into newline characters, and all data +(\\), will be changed into newline characters, and all data after the first % will be sent to the command as standard -input. There is no way to split a single command line onto multiple -lines, like the shell's trailing "\e". +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 (i.e., don't start with *), the command will be run when +restricted (i.e., aren't *), the command will be run when .I either field matches the current time. For example, .br @@ -252,19 +214,16 @@ or other facilities, were startup. This is due to the boot order sequence of the machine. .SH EXAMPLE CRON FILE - -The following lists an example of a user crontab file. - .nf -# use /bin/bash to run commands, instead of the default /bin/sh -SHELL=/bin/bash +# 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 \(em output mailed to paul +# 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?% @@ -338,13 +297,12 @@ cron(8), crontab(1) When specifying day of week, both day 0 and day 7 will be considered Sunday. BSD and AT&T 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 AT&T or BSD cron \(em they want -to see "1\-3" or "7,8,9" ONLY. +Lists and ranges are allowed to co-exist in the same field. "1-3,7-9" would +be rejected by AT&T 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". +Ranges can include "steps", so "1-9/2" is the same as "1,3,5,7,9". .PP -Months or days of the week can be specified by name. +Names of monts or days of the week can be specified by name. .PP Environment variables can be set in the crontab. In BSD or AT&T, the environment handed to child processes is basically the one from /etc/rc. @@ -420,5 +378,5 @@ A warning will be written to syslog. Paul Vixie is the author of .I cron and original creator of this manual page. This page has also been modified for -Debian by Steve Greenland, Javier Fernandez-Sanguino, Christian Kastner and -Christian Pekeler. +Debian by Steve Greenland, Javier Fernandez-Sanguino, Christian Kastner, +Christian Pekeler, Georges Khaznadar.