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documentation: extensive editing of info manual after a note from Paul Vixie.

Browse source 
Paul has been in touch to say that the crontab format was not his invention,
and that his program was based off of V7's cron's functionality, not later
AT&T and Berkeley ones.

Thus the mcron manual is edited extensively to emphasise more the POSIX
standard crontab format, and to point out a more accurate history of cron
developments.

* doc/mcron.texi: small changes throughout the document.
This commit is contained in:
Dale Mellor 2022-01-10 15:52:23 +00:00
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doc/mcron.texi
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@ -11,7 +11,7 @@
@copying This manual is for GNU mcron (version @value{VERSION}), which is a @copying This manual is for GNU mcron (version @value{VERSION}), which is a
program for running jobs at scheduled times. program for running jobs at scheduled times.
Copyright @copyright{} 2003, 2005, 2006, 2012, 2014 Dale Mellor Copyright @copyright{} 2003, 2005, 2006, 2012, 2014, 2022 Dale Mellor
Copyright @copyright{} 2018 Mathieu Lirzin Copyright @copyright{} 2018 Mathieu Lirzin
@quotation @quotation
@ -73,7 +73,7 @@ running jobs at scheduled times.
Simple examples Simple examples
* Guile Simple Examples:: * Guile Simple Examples::
* Vixie Simple Examples:: * POSIX Simple Examples::
Full available syntax Full available syntax
@ -107,9 +107,9 @@ Guile modules
* The base module:: The job list and execution loop. * The base module:: The job list and execution loop.
* The redirect module:: Sending output of jobs to a mail box. * The redirect module:: Sending output of jobs to a mail box.
* The vixie-time module:: Parsing vixie-style time specifications. * The vixie-time module:: Parsing Vixie-style time specifications.
* The job-specifier module:: All commands for scheme configuration files. * The job-specifier module:: All commands for Scheme configuration files.
* The vixie-specification module:: Commands for reading vixie-style crontabs. * The vixie-specification module:: Commands for reading Vixie-style crontabs.
@end detailmenu @end detailmenu
@end menu @end menu
@ -119,29 +119,31 @@ Guile modules
@cindex introduction @cindex introduction
@cindex mcron @cindex mcron
The mcron program represents a complete re-think of the cron concept The mcron program represents a complete re-think of the cron concept
originally found in the Berkeley and AT&T unices, and subsequently originally found in V7 Unix, ratified by POSIX, and re-realized by Paul Vixie
rationalized by Paul Vixie. The original idea was to have a daemon for the free world. The original idea was to have a daemon that wakes up
that wakes up every minute, scans a set of files under a special every minute, scans a set of files under a special directory, and determines
directory, and determines from those files if any shell commands from those files if any shell commands should be executed in this minute.
should be executed in this minute.
The new idea is to read the required command instructions, work out The new@footnote{With retrospect, not so new: AT&T and Berkeley Unices had a
which command needs to be executed next, and then sleep until the cron program which also implemented this 'new' idea, though Dale Mellor was
inferred time has arrived. On waking the commands are run, and the unaware of this at the time of mcron's conception and initial development.
time of the next command is computed. Furthermore, the specifications The Wikipedia page for cron appears quite authoritative and is a good source
are written in scheme, allowing at the same time simple command of information about the history of cron.} idea is to read the required
execution instructions and very much more flexible ones to be composed command instructions, work out which command needs to be executed next, and
than the original Vixie format. This has several useful advantages then sleep until the inferred time has arrived. On waking the commands are
over the original idea. (Changes to user crontabs are signalled run, and the time of the next command is computed. Furthermore, the
directly to mcron by the crontab program; cron must still scan the specifications are written in Scheme, allowing at the same time simple command
/etc/crontab file once every minute, although use of this file is execution instructions and very much more flexible ones to be composed than
highly discouraged and this behaviour can be turned off). the POSIX format allows. This has several useful advantages over the original
idea.
@cindex advantages of mcron @cindex advantages of mcron
@itemize @bullet @itemize @bullet
@item @item
Does not consume CPU resources when not needed. Many cron daemons only Does not consume CPU resources when not needed. Many cron daemons
run jobs once an hour, or even just once a day. only run jobs once an hour, or even just once a day. Busy computers
with high memory pressure can keep the mcron program swapped out to
disk more of the time.
@item @item
Can easily allow for finer time-points to be specified, Can easily allow for finer time-points to be specified,
i.e. seconds. In principle this could be extended to microseconds, but i.e. seconds. In principle this could be extended to microseconds, but
@ -151,12 +153,12 @@ Times can be more or less regular. For example, a job that runs
every 17 hours can be specified, or a job that runs on the first every 17 hours can be specified, or a job that runs on the first
Sunday of every month. Sunday of every month.
@item @item
Times can be dynamic. Arbitrary Guile (scheme) code can be provided to Times can be dynamic. Arbitrary Guile (Scheme) code can be provided to
compute the next time that a command needs to be run. This could, for compute the next time that a command needs to be run. This could, for
example, take the system load into consideration. example, take the system load into consideration.
@item @item
Turns out to be easy to provide complete backwards compatibility with Turns out to be easy to provide complete backwards compatibility with
Vixie cron. the POSIX cron specification.
@item @item
Each user looks after their own files in their own directory. They can use Each user looks after their own files in their own directory. They can use
more than one to break up complicated cron specifications. more than one to break up complicated cron specifications.
@ -168,9 +170,10 @@ concerns that surround all existing cron programs.
The user can obtain an advance schedule of all the jobs that are due The user can obtain an advance schedule of all the jobs that are due
to run. to run.
@item @item
Vixie cron is implemented in 4500 lines of C code; mcron is 2000 lines Vixie cron is implemented in 4500 lines of C code; mcron was 2000
of scheme, despite the fact that it offers many more features and much lines of Scheme (it has grown a little fatter since), despite the fact
more flexibility, and complete compatibility with Vixie cron. that it offered many more features and much more flexibility, and
complete compatibility with Vixie cron and the POSIX specification.
@end itemize @end itemize
A full discussion of the design and philosophy of mcron can be found A full discussion of the design and philosophy of mcron can be found
@ -187,10 +190,10 @@ examples show how to create the command descriptions, and subsequently
how to run mcron to make them happen. how to run mcron to make them happen.
@menu @menu
* Guile Simple Examples:: * Guile Simple Examples::
* Vixie Simple Examples:: * POSIX Simple Examples::
@end menu @end menu
@node Guile Simple Examples, Vixie Simple Examples, Simple examples, Simple examples @node Guile Simple Examples, POSIX Simple Examples, Simple examples, Simple examples
@section Guile @section Guile
@cindex guile examples @cindex guile examples
@cindex examples, guile @cindex examples, guile
@ -236,11 +239,11 @@ you want and pass it as an argument to @code{mcron}, or even pipe the
commands into the standard input. commands into the standard input.
@node Vixie Simple Examples, , Guile Simple Examples, Simple examples @node POSIX Simple Examples, , Guile Simple Examples, Simple examples
@section Vixie @section POSIX
@cindex examples @cindex examples
@cindex examples, vixie @cindex examples, POSIX
@cindex vixie examples @cindex POSIX examples
You have an executable @code{my-program} in your home directory, which You have an executable @code{my-program} in your home directory, which
you want to run every hour. Create a file @code{job.vixie} in directory you want to run every hour. Create a file @code{job.vixie} in directory
@code{~/.cron} with the following contents @code{~/.cron} with the following contents
@ -251,13 +254,14 @@ you want to run every hour. Create a file @code{job.vixie} in directory
then run the command @code{mcron}. then run the command @code{mcron}.
@cindex vixie compatibility @cindex Vixie compatibility
@cindex compatibility @cindex compatibility
Alternatively (full compatibility with Vixie cron), set your Alternatively (full compatibility with Vixie cron), set your
environment variable @code{EDITOR} to your favorite editor, run environment variable @code{EDITOR} to your favorite editor, run
@code{crontab -e}, put the above line into the edit buffer, save and @code{crontab -e}, put the above line into the edit buffer, save and
exit. For this to work the @code{cron} daemon must be already running exit. For this to work the @code{cron} daemon must be already running
on your system, as root. on your system, as root. This style of operations is considered
deprecated.
@node Syntax, Invoking, Simple examples, Top @node Syntax, Invoking, Simple examples, Top
@chapter Full available syntax @chapter Full available syntax
@ -272,13 +276,14 @@ on your system, as root.
@cindex guile syntax @cindex guile syntax
@cindex syntax, guile @cindex syntax, guile
@findex job @findex job
In Guile-formatted configuration files each command that needs executing is In Guile-formatted configuration files each command that needs
introduced with the @code{job} function. This function always takes two executing is introduced with the @code{job} function. This function
arguments, the first a time specification, and the second a command takes two mandatory arguments, the first a time specification, and the
specification. An optional third argument may contain a string to display second a command specification. An optional third argument may
when this job is listed in a schedule. Additionally a @var{user} keyword contain a string to display when this job is listed in a schedule.
argument can be supplied to use a different user than the one defined in Additionally a @var{user} keyword argument can be supplied to use a
@code{configuration-user} global variable. different user than the one defined in the @code{configuration-user}
global variable.
@cindex time specification, procedure @cindex time specification, procedure
@cindex procedure time specification @cindex procedure time specification
@ -290,15 +295,15 @@ be run. The following functions are available to facilitate the
computation: computation:
@findex next-second-from @findex next-second-from
@code{(next-second-from time . args)} without arguments this @code{(next-second-from time . args)} without arguments this returns
returns the second after the current one. With the extra arguments, the second after the given @code{time}. If an extra argument is
these form a list of seconds in the minute when the action should run, supplied, it should form a list of seconds in the minute when the
and the function will return the time of the next allowed second action should run, and the function will return the time of the next
(which may be in the next minute of the hour). @footnote{Note that allowed second (which may be in the next minute of the hour).
while commands can be scheduled to run at any second, it is unlikely @footnote{Note that while commands can be scheduled to run at any
that they will be executed then but some time shortly thereafter, second, it is unlikely that they will be executed then but some time
depending on the load on the system and the number of jobs that mcron shortly thereafter, depending on the load on the system and the number
has to start at the same time.} of jobs that mcron has to start at the same time.}
@findex next-minute-from @findex next-minute-from
@findex next-hour-from @findex next-hour-from
@ -310,11 +315,18 @@ Similarly to @code{next-second-from}, there are also
@code{next-minute-from}, @code{next-hour-from}, @code{next-day-from}, @code{next-minute-from}, @code{next-hour-from}, @code{next-day-from},
@code{next-week-from}, @code{next-month-from}, @code{next-year-from}. @code{next-week-from}, @code{next-month-from}, @code{next-year-from}.
@findex iota
Furthermore, the optional argument can be fulfilled by the Guile
function @code{(iota count . start step)}, which will provide a list
of @code{count} values from @code{start}, with the step if given. For
example @code{(iota 10 0 2)} will yield the list @code{'(0 2 4 6 8)}.
@findex range @findex range
Furthermore, the optional argument can be fulfilled by the function As a convenience, mcron itself provides a function @code{range}, such
@code{(range start end . step)}, which will provide a list of values that @code{(range start end . step)} will provide a list of values
from start to (but not including) end, with the step if given. For from start to (but not including) end, with the step if given. For
example @code{(range 0 10 2)} will yield the list @code{'(0 2 4 6 8)}. example @code{(range 0 10 2)} will also yield the list @code{'(0 2 4 6
8)}.
@findex next-second @findex next-second
@findex next-minute @findex next-minute
@ -326,57 +338,59 @@ example @code{(range 0 10 2)} will yield the list @code{'(0 2 4 6 8)}.
@cindex time specification, list @cindex time specification, list
@cindex list time specification @cindex list time specification
If the first argument to the @code{job} function is a list, it is If the first argument to the @code{job} function is a list, it is
taken to be program code made up of the functions @code{(next-second taken to be program code (technically known as an @emph{S-expression})
. args)}, @code{(next-minute...)}, etc, where the optional arguments made up of the functions @code{(next-second . args)},
can be supplied with the @code{(range)} function above (these @code{(next-minute...)}, etc, where the optional arguments can be
supplied with the @code{iota} or @code{range} functions above (these
functions are analogous to the ones above except that they implicitly functions are analogous to the ones above except that they implicitly
assume the current time; it is supplied by the mcron base when the assume the current time; it is supplied by mcron when the list is
list is eval'd). @emph{eval}'d).
@cindex time specification @cindex time specification
@cindex time specification, string @cindex time specification, string
@cindex string time specification @cindex string time specification
@cindex time specification, vixie-style @cindex time specification, POSIX-style
@cindex vixie-style time specification @cindex POSIX-style time specification
If the first argument to the @code{job} function is a string, it is If the first argument to the @code{job} function is a string, it is
expected to be a Vixie cron-style time specification. See the section expected to be a POSIX crontab-style time specification. See the
on Vixie syntax for this. section on Vixie syntax for this.
@cindex job execution @cindex job execution
@cindex command execution @cindex command execution
@cindex execution @cindex execution
The second argument to the @code{(job)} function can be either a string, a The second argument to the @code{job} function can be either a string,
list, or a function. The command is executed in the home directory and with a list, or a function. The command is executed in the home directory
the UID of @var{user}. If a string is passed, it is assumed to be shell and with the UID of @var{user}. If a string is passed, it is assumed
script and is executed with the user's default shell. If a list is passed it to be shell script and is executed with the user's default shell. If
is assumed to be scheme code and is eval'd as such. A supplied function a list is passed it is assumed to be Scheme code and is @emph{eval}'d
should take exactly zero arguments, and will be called at the pertinent times. as such. A supplied function should take exactly zero arguments, and
will be called at the pertinent times.
@subsection Sending output as e-mail @subsection Sending output as e-mail
@cindex email output @cindex email output
@cindex email from guile script @cindex email from guile script
@cindex standard input to commands @cindex standard input to commands
@findex with-mail-out @findex with-mail-out
When jobs are specified in a vixie-style configuration, the command is When jobs are specified in a POSIX-style configuration, the command is
broken at a percentage sign, and the stuff that comes after this is broken at a percentage sign, and the stuff that comes after this is
sent into the command's standard input. Furthermore, any output from sent into the command's standard input. Furthermore, any output from
the command is mailed to the user. This functionality is provided for the command is mailed to the user. This functionality is provided in
compatibility with Vixie cron, but it is also available to scheme mcron for compatibility with Vixie cron, but it is also available to
configuration files. The command (with-mail-out action . user) can be Scheme configuration files. The command (with-mail-out action . user)
used to direct output from the action (which may be a procedure, list, can be used to direct standard output from the action (which may be a
or string) into an e-mail to the user. procedure, list, or string) into an e-mail to the user.
In the case that the action is a string, then percentage signs are In the case that the action is a string, then percentage signs are
processed as per the vixie specifications, and information is piped to processed as per the POSIX specifications, and information is piped to
the shell command's standard input. the shell command's standard input.
@subsection Setting environment variables @subsection Setting environment variables
@cindex environment variables in scheme @cindex environment variables in Scheme
@cindex setting environment variables @cindex setting environment variables
@findex append-environment-mods @findex append-environment-mods
Also for compatibility with Vixie cron, mcron has the ability to set Also for compatibility with Vixie cron, mcron has the ability to set
environment variables in configuration files. To access this environment variables in configuration files. To access this
functionality from a scheme configuration file, use the command functionality from a Scheme configuration file, use the command
(append-environment-mods name value), where name is the name of an (append-environment-mods name value), where name is the name of an
environment variable, and value is the value put to it. A value of #f environment variable, and value is the value put to it. A value of #f
will remove the variable from the environment. will remove the variable from the environment.
@ -407,9 +421,10 @@ demonstrate how to code around them.
@node AT commands, Every second Sunday, Extended Guile examples, Extended Guile examples @node AT commands, Every second Sunday, Extended Guile examples, Extended Guile examples
@subsection Synthesizing ``at'' commands @subsection Synthesizing ``at'' commands
@cindex at command @cindex at command
The current implementation of mcron does not provide for an at command The current implementation of mcron does not provide for an @emph{at}
(a command-line program that allows the user to specify that a job command (a command-line program that allows the user to specify that a
runs exactly once at a certain time). This can, however, be achieved. job runs exactly once at a certain time). This can, however, be
achieved.
Suppose the program @code{my-program} needs to be run at midnight Suppose the program @code{my-program} needs to be run at midnight
tonight. A Guile script like the following would work (but a printed tonight. A Guile script like the following would work (but a printed
@ -427,7 +442,7 @@ superfluous entries).
@cindex examples, every second sunday @cindex examples, every second sunday
To run @code{my-program} on the second Sunday of every month, a Guile To run @code{my-program} on the second Sunday of every month, a Guile
script like the following should suffice (it is left as an exercise to script like the following should suffice (it is left as an exercise to
the student to understand how this works!). the student to understand how this works!)
@example @example
(job (lambda (current-time) (job (lambda (current-time)
@ -508,11 +523,11 @@ second-to-last day of every month.
@node Vixie Syntax, , Extended Guile examples, Syntax @node Vixie Syntax, , Extended Guile examples, Syntax
@section Vixie @section Vixie
@cindex syntax, vixie @cindex syntax, Vixie
@cindex vixie syntax @cindex Vixie syntax
@cindex vixie definition @cindex Vixie definition
@cindex vixie compatibility @cindex Vixie compatibility
@cindex compatibility, vixie @cindex compatibility, Vixie
@emph{NOTE} that this section is definitive. If there is a difference in @emph{NOTE} that this section is definitive. If there is a difference in
behaviour between the mcron program and this part of the manual, then behaviour between the mcron program and this part of the manual, then
there is a bug in the program. This section is also copied verbatim there is a bug in the program. This section is also copied verbatim
@ -531,7 +546,7 @@ effect. However, if it appears on its own, the effect is to say
specification into account.'' Mcron has been coded to mimic this specification into account.'' Mcron has been coded to mimic this
behaviour as a special case (unmodified mcron logic implies that this behaviour as a special case (unmodified mcron logic implies that this
date specification would cause jobs to run on the last day of the date specification would cause jobs to run on the last day of the
previous month). previous month, which will never happen).
@cindex thirteenth month of year @cindex thirteenth month of year
@cindex 13th month of year @cindex 13th month of year
@ -580,7 +595,7 @@ user.
@node Crontab file, Incompatibilities with old Unices, Paul Vixie's copyright, Vixie Syntax @node Crontab file, Incompatibilities with old Unices, Paul Vixie's copyright, Vixie Syntax
@subsection Crontab files @subsection Crontab files
@cindex crontab file @cindex crontab file
@cindex vixie crontab file @cindex Vixie crontab file
A @code{crontab} file contains instructions to the @code{cron} daemon A @code{crontab} file contains instructions to the @code{cron} daemon
of the general form: ``run this command at this time on this date''. 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 Each user has their own crontab, and commands in any given crontab
@ -588,7 +603,7 @@ will be executed as the user who owns the crontab. Uucp and News will
usually have their own crontabs, eliminating the need for explicitly usually have their own crontabs, eliminating the need for explicitly
running @code{su} as part of a cron command. running @code{su} as part of a cron command.
@cindex comments, vixie-style @cindex comments, Vixie-style
Blank lines and leading spaces and tabs are ignored. Lines whose first Blank lines and leading spaces and tabs are ignored. Lines whose first
non-space character is a pound-sign (#) are comments, and are ignored. 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 Note that comments are not allowed on the same line as cron commands, since
@ -598,7 +613,7 @@ allowed on the same line as environment variable settings.
An active line in a crontab will be either an environment setting or a cron An active line in a crontab will be either an environment setting or a cron
command. An environment setting is of the form, command. An environment setting is of the form,
@cindex environment setting, vixie-style @cindex environment setting, Vixie-style
@example @example
name = value name = value
@end example @end example
@ -649,8 +664,8 @@ time, @strong{and} when at least one of the two day fields (day of month, or day
match the current time (see ``Note'' below). @code{cron} examines cron entries once every minute. match the current time (see ``Note'' below). @code{cron} examines cron entries once every minute.
The time and date fields are: The time and date fields are:
@cindex vixie time specification fields @cindex Vixie time specification fields
@cindex fields, vixie time specification @cindex fields, Vixie time specification
@multitable @columnfractions .2 .5 @multitable @columnfractions .2 .5
@item Field @tab Allowed values @item Field @tab Allowed values
@item ----- @tab -------------- @item ----- @tab --------------
@ -663,17 +678,17 @@ The time and date fields are:
A field may be an asterisk (*), which always stands for ``first-last''. A field may be an asterisk (*), which always stands for ``first-last''.
@cindex ranges in vixie time specifications @cindex ranges in Vixie time specifications
Ranges of numbers are allowed. Ranges are two numbers separated Ranges of numbers are allowed. Ranges are two numbers separated
with a hyphen. The specified range is inclusive. For example, 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. and 11.
@cindex lists in vixie time specifications @cindex lists in Vixie time specifications
Lists are allowed. A list is a set of numbers (or ranges) 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''.
@cindex steps in vixie time specifications @cindex steps in Vixie time specifications
Step values can be used in conjunction with ranges. Following Step values can be used in conjunction with ranges. Following
a range with ``/<number>'' specifies skips of the number's value 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 through the range. For example, ``0-23/2'' can be used in the hours
@ -682,15 +697,15 @@ 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 also permitted after an asterisk, so if you want to say ``every two
hours'', just use ``*/2''. hours'', just use ``*/2''.
@cindex names in vixie-style time specifications @cindex names in Vixie-style time specifications
Names can also be used for the ``month'' and ``day of week'' Names can also be used for the ``month'' and ``day of week''
fields. Use the first three letters of the particular fields. Use the first three letters of the particular
day or month (case doesn't matter). Ranges or day or month (case doesn't matter). Ranges or
lists of names are not allowed. @footnote{Mcron allows any alphabetic lists of names are not allowed. @footnote{Mcron allows any alphabetic
characters after a name, so full names of days or months are also valid.} characters after a name, so full names of days or months are also valid.}
@cindex % character on vixie-style commands @cindex % character on Vixie-style commands
@cindex standard input, vixie-style @cindex standard input, Vixie-style
The ``sixth'' field (the rest of the line) specifies the command to be The ``sixth'' field (the rest of the line) specifies the command to be
run. run.
The entire command portion of the line, up to a newline or % The entire command portion of the line, up to a newline or %
@ -701,8 +716,8 @@ Percent-signs (%) in the command, unless escaped with backslash
after the first % will be sent to the command as standard after the first % will be sent to the command as standard
input. input.
@cindex day specification, vixie-style @cindex day specification, Vixie-style
@cindex vixie-style day specification @cindex Vixie-style day specification
Note: The day of a command's execution can be specified by two Note: The day of a command's execution can be specified by two
fields -- day of month, and day of week. If both fields are fields -- day of month, and day of week. If both fields are
restricted (ie, aren't *), the command will be run when restricted (ie, aren't *), the command will be run when
@ -735,7 +750,7 @@ MAILTO=paul
@node Incompatibilities with old Unices, , Crontab file, Vixie Syntax @node Incompatibilities with old Unices, , Crontab file, Vixie Syntax
@subsection Extensions and incompatibilities @subsection Extensions and incompatibilities
@cindex incompatibilities with old Unices @cindex incompatibilities with old Unices
@cindex extensions, vixie over old Unices @cindex extensions, Vixie over old Unices
This section lists differences between Paul Vixie's cron and the This section lists differences between Paul Vixie's cron and the
olde-worlde BSD and AT&T programs, for the benefit of system olde-worlde BSD and AT&T programs, for the benefit of system
administrators and users who are upgrading all the way. administrators and users who are upgrading all the way.
@ -790,7 +805,7 @@ this daemon process is shared by, and under control of, all the users
of the system it is possible (though very unlikely) that it may become of the system it is possible (though very unlikely) that it may become
unusable, hence the recommendation to use the mcron personality. unusable, hence the recommendation to use the mcron personality.
@cindex deprecated, vixie personality @cindex deprecated, Vixie personality
Furthermore, the Vixie personality is considered deprecated by this Furthermore, the Vixie personality is considered deprecated by this
author (it offers not a single advantage over the mcron personality, author (it offers not a single advantage over the mcron personality,
and bloats the code by a factor of three). It is unlikely that this and bloats the code by a factor of three). It is unlikely that this
@ -826,7 +841,7 @@ look in the user's cron configuration directories: these are ~/.cron
environment variable, or ~/.config/cron if this variable is not set. environment variable, or ~/.config/cron if this variable is not set.
In any case, files which end in the extension .vixie or .vix will be In any case, files which end in the extension .vixie or .vix will be
assumed to contain Vixie-style crontabs, and files ending .guile or assumed to contain Vixie-style crontabs, and files ending .guile or
.gle will be assumed to contain scheme code and will be executed as .gle will be assumed to contain Scheme code and will be executed as
such; ANY OTHER FILES WILL BE IGNORED - specify a file name of ``-'' such; ANY OTHER FILES WILL BE IGNORED - specify a file name of ``-''
and then pipe the files into the standard input if you really want to and then pipe the files into the standard input if you really want to
read them, possibly using the @code{stdin} option to specify the type read them, possibly using the @code{stdin} option to specify the type
@ -1025,12 +1040,12 @@ Delete the user's crontab file, and exit.
@cindex creating a crontab @cindex creating a crontab
@item -e @item -e
@item --edit @item --edit
Using the editor specified in the user's VISUAL or EDITOR environment Using the editor specified in the user's @code{VISUAL} or
variables, allow the user to edit their crontab. Once the user exits the @code{EDITOR} environment variables, allow the user to edit their
editor, the crontab is checked for parseability, and if it is okay crontab. Once the user exits the editor, the crontab is checked for
then it is installed as the user's new crontab and the daemon is parseability, and if it is okay then it is installed as the user's new
notified that a change has taken place, so that the new file will crontab and the daemon is notified that a change has taken place, so
become immediately effective. that the new file will become immediately effective.
@end table @end table
@ -1104,10 +1119,10 @@ Crontab has been run with the -u option by a user other than
root. Only root is allowed to use this option. root. Only root is allowed to use this option.
@item 9 @item 9
An invalid vixie-style time specification has been supplied. An invalid Vixie-style time specification has been supplied.
@item 10 @item 10
An invalid vixie-style job specification has been supplied. An invalid Vixie-style job specification has been supplied.
@item 11 @item 11
A bad line has been seen in /etc/crontab. A bad line has been seen in /etc/crontab.
@ -1153,16 +1168,16 @@ of next week, for example). Finally, it may be the wish of the user to
provide a program with the functionality of mcron plus a bit extra. provide a program with the functionality of mcron plus a bit extra.
The base module maintains mcron's internal job lists, and provides the The base module maintains mcron's internal job lists, and provides the
main wait-run-wait loop that is mcron's main function. It also main wait-run-wait loop that is mcron's primary function. It also
introduces the facilities for accumulating a set of environment introduces the facilities for accumulating a set of environment
modifiers, which take effect when jobs run. modifiers, which take effect when jobs run.
@menu @menu
* The base module:: The job list and execution loop. * The base module:: The job list and execution loop.
* The redirect module:: Sending output of jobs to a mail box. * The redirect module:: Sending output of jobs to a mail box.
* The vixie-time module:: Parsing vixie-style time specifications. * The vixie-time module:: Parsing Vixie-style time specifications.
* The job-specifier module:: All commands for scheme configuration files. * The job-specifier module:: All commands for Scheme configuration files.
* The vixie-specification module:: Commands for reading vixie-style crontabs. * The vixie-specification module:: Commands for reading Vixie-style crontabs.
@end menu @end menu
@node The base module, The redirect module, Guile modules, Guile modules @node The base module, The redirect module, Guile modules, Guile modules
@ -1270,7 +1285,7 @@ fully in @ref{Guile Syntax}.
This module is introduced to a program by @code{(use-modules (mcron This module is introduced to a program by @code{(use-modules (mcron
vixie-time))}. vixie-time))}.
This module provides a single method for converting a vixie-style time This module provides a single method for converting a Vixie-style time
specification into a procedure which can be used as the specification into a procedure which can be used as the
@code{next-time-function} to the base @code{add-job} procedure, or to @code{next-time-function} to the base @code{add-job} procedure, or to
the @code{job-specifier} @code{job} procedure. See @ref{Vixie Syntax} the @code{job-specifier} @code{job} procedure. See @ref{Vixie Syntax}
@ -1278,7 +1293,7 @@ for full details of the allowed format for the time string.
@deffn{Scheme procedure} parse-vixie-time time-string @deffn{Scheme procedure} parse-vixie-time time-string
The single argument @var{time-string} should be a string containing a The single argument @var{time-string} should be a string containing a
vixie-style time specification, and the return value is the required Vixie-style time specification, and the return value is the required
procedure. procedure.
@end deffn @end deffn
@ -1300,7 +1315,7 @@ configuration files, namely @code{range}, @code{next-year-from},
and last but not least, @code{job}. See @ref{Guile Syntax} for full and last but not least, @code{job}. See @ref{Guile Syntax} for full
details. details.
Once this module is loaded, a scheme configuration file can be used to Once this module is loaded, a Scheme configuration file can be used to
put jobs onto the job list simply by @code{load}ing the file. put jobs onto the job list simply by @code{load}ing the file.
@node The vixie-specification module, , The job-specifier module, Guile modules @node The vixie-specification module, , The job-specifier module, Guile modules