Updated the version to 1.0.2. Made minor edits to the manual, especially with regard to the more esoteric examples.
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dale_mellor
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2 changed files with 129 additions and 117 deletions
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mcron.texinfo.in
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mcron.texinfo.in
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@ -8,7 +8,7 @@
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@copying
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Copyright (C) 2003, 2005 Dale Mellor
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This is free software. See the source files for the terms of the
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This is free software. See the source files for the terms of the
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copyright.
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@ignore
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@ -128,45 +128,45 @@ Guile modules
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@cindex mcron
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The mcron program represents a complete re-think of the cron concept
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originally found in the Berkeley and AT&T unices, and subsequently
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rationalized by Paul Vixie. The original idea was to have a daemon
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rationalized by Paul Vixie. The original idea was to have a daemon
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that wakes up every minute, scans a set of files under a special
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directory, and determines from those files if any shell commands
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should be executed in this minute.
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The new idea is to read the required command instructions, work out
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which command needs to be executed next, and then sleep until the
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inferred time has arrived. On waking the commands are run, and the
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time of the next command is computed. Furthermore, the specifications
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inferred time has arrived. On waking the commands are run, and the
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time of the next command is computed. Furthermore, the specifications
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are written in scheme, allowing at the same time simple command
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execution instructions and very much more flexible ones to be composed
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than the original Vixie format. This has several useful advantages
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than the original Vixie format. This has several useful advantages
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over the original idea.
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@cindex advantages of mcron
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@itemize @bullet
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@item
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Does not consume CPU resources when not needed. Many cron daemons only
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Does not consume CPU resources when not needed. Many cron daemons only
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run jobs once an hour, or even just once a day.
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@item
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Can easily allow for finer time-points to be specified,
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i.e. seconds. In principle this could be extended to microseconds, but
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i.e. seconds. In principle this could be extended to microseconds, but
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this is not implemented.
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@item
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Times can be more or less regular. For example, a job that runs
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Times can be more or less regular. For example, a job that runs
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every 17 hours can be specified, or a job that runs on the first
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Sunday of every month.
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@item
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Times can be dynamic. Arbitrary Guile (scheme) code can be provided to
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compute the next time that a command needs to be run. This could, for
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Times can be dynamic. Arbitrary Guile (scheme) code can be provided to
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compute the next time that a command needs to be run. This could, for
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example, take the system load into consideration.
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@item
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Turns out to be easy to provide complete backwards compatibility with
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Vixie cron.
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@item
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Each user looks after his own files in his own directory. He can use
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Each user looks after his own files in his own directory. He can use
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more than one to break up complicated cron specifications.
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@item
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Each user can run his own daemon. This removes the need for suid
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Each user can run his own daemon. This removes the need for suid
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programs to manipulate the crontabs, and eliminates many security
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concerns that surround all existing cron programs.
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@item
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@ -185,8 +185,8 @@ in the white paper at http://www.gnu.org/software/mcron/design.html.
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@node Simple examples, Syntax, Introduction, Top
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@chapter Simple examples
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The vast majority of uses of cron are sublimely simple: run a program
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every hour, or every day. With this in mind the design of mcron has
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been to allow such simple specifications to be made easily. The
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every hour, or every day. With this in mind the design of mcron has
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been to allow such simple specifications to be made easily. The
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examples show how to create the command descriptions, and subsequently
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how to run mcron to make them happen.
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@menu
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@ -200,7 +200,7 @@ how to run mcron to make them happen.
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@cindex examples, guile
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@cindex example, run a program every hour
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You have an executable @code{my-program} in your home directory, which
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you want to run every hour. Create a file @code{job.guile} in directory
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you want to run every hour. Create a file @code{job.guile} in directory
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@code{~/.cron} with the following contents
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@example
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@ -233,7 +233,7 @@ and run the @code{mcron} command.
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If you want to run other jobs, you can either add more lines to this
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file, or you can create other files in your @code{.cron} directory
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with the @code{.guile} extension. Alternatively, you can use any file
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with the @code{.guile} extension. Alternatively, you can use any file
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you want and pass it as an argument to @code{mcron}, or even pipe the
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commands into the standard input.
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@ -244,7 +244,7 @@ commands into the standard input.
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@cindex examples, vixie
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@cindex vixie examples
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You have an executable @code{my-program} in your home directory, which
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you want to run every hour. Create a file @code{job.vixie} in directory
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you want to run every hour. Create a file @code{job.vixie} in directory
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@code{~/.cron} with the following contents
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@example
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@ -258,7 +258,7 @@ then run the command @code{mcron}.
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Alternatively (full compatibility with Vixie cron), set your
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environment variable @code{EDITOR} to your favorite editor, run
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@code{crontab -e}, put the above line into the edit buffer, save and
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exit. For this to work the @code{cron} daemon must be already running
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exit. For this to work the @code{cron} daemon must be already running
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on your system, by root.
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@node Syntax, Invoking, Simple examples, Top
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@ -275,26 +275,26 @@ on your system, by root.
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@cindex syntax, guile
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@findex job
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In Guile-formatted configuration files each command that needs
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executing is introduced with the @code{job} function. This function
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executing is introduced with the @code{job} function. This function
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always takes two arguments, the first a time specification, and the
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second a command specification. An optional third argument may contain
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second a command specification. An optional third argument may contain
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a string to display when this job is listed in a schedule.
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@cindex time specification, procedure
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@cindex procedure time specification
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The first argument can be a procedure, a list, or a string. If a
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The first argument can be a procedure, a list, or a string. If a
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function is supplied, it must take exactly one argument, which will be
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the ``current'' time in UNIX format, and the return value of the
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function must be the time in UNIX format when this action should next
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be run. The following functions are available to facilitate the
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be run. The following functions are available to facilitate the
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computation:
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@findex next-second-from
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@code{(next-second-from time . args)} without arguments this
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returns the second after the current one. With the extra arguments,
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returns the second after the current one. With the extra arguments,
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these form a list of seconds in the minute when the action should run,
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and the function will return the time of the next allowed second
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(which may be in the next minute of the hour). @footnote{Note that
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(which may be in the next minute of the hour). @footnote{Note that
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while commands can be scheduled to run at any second, it is unlikely
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that they will be executed then but some time shortly thereafter,
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depending on the load on the system and the number of jobs that mcron
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@ -313,7 +313,7 @@ Similarly to @code{next-second-from}, there are also
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@findex range
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Furthermore, the optional argument can be fulfilled by the function
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@code{(range start end . step)}, which will provide a list of values
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from start to (but not including) end, with the step if given. For
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from start to (but not including) end, with the step if given. For
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example @code{(range 0 10 2)} will yield the list @code{'(0 2 4 6 8)}.
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@findex next-second
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@ -339,18 +339,18 @@ list is eval'd).
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@cindex time specification, vixie-style
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@cindex vixie-style time specification
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If the first argument to the @code{job} function is a string, it is
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expected to be a Vixie cron-style time specification. See the section
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expected to be a Vixie cron-style time specification. See the section
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on Vixie syntax for this.
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@cindex job execution
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@cindex command execution
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@cindex execution
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The second argument to the @code{(job)} function can be either a
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string, a list, or a function. In all cases the command is executed in
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the user's home directory, under the user's own UID. If a string is
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string, a list, or a function. In all cases the command is executed in
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the user's home directory, under the user's own UID. If a string is
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passed, it is assumed to be shell script and is executed with the
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user's default shell. If a list is passed it is assumed to be scheme
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code and is eval'd as such. A supplied function should take exactly
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user's default shell. If a list is passed it is assumed to be scheme
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code and is eval'd as such. A supplied function should take exactly
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zero arguments, and will be called at the pertinent times.
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@subsection Sending output as e-mail
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@ -360,10 +360,10 @@ zero arguments, and will be called at the pertinent times.
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@findex with-mail-out
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When jobs are specified in a vixie-style configuration, the command is
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broken at a percentage sign, and the stuff that comes after this is
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sent into the command's standard input. Furthermore, any output from
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the command is mailed to the user. This functionality is provided for
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sent into the command's standard input. Furthermore, any output from
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the command is mailed to the user. This functionality is provided for
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compatibility with Vixie cron, but it is also available to scheme
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configuration files. The command (with-mail-out action . user) can be
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configuration files. The command (with-mail-out action . user) can be
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used to direct output from the action (which may be a procedure, list,
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or string) into an e-mail to the user.
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@ -376,10 +376,10 @@ the shell command's standard input.
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@cindex setting environment variables
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@findex append-environment-mods
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Also for compatibility with Vixie cron, mcron has the ability to set
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environment variables in configuration files. To access this
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environment variables in configuration files. To access this
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functionality from a scheme configuration file, use the command
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(append-environment-mods name value), where name is the name of an
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environment variable, and value is the value put to it. A value of #f
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environment variable, and value is the value put to it. A value of #f
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will remove the variable from the environment.
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Note that environment modifications are accumulated as the
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@ -394,7 +394,7 @@ before the job specification in the configuration file.
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@cindex extended guile examples
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While Guile gives you flexibility to do anything, and the power to
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represent complex requirements succinctly, things are not always as
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they seem. The following examples illustrate some pitfalls, and
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they seem. The following examples illustrate some pitfalls, and
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demonstrate how to code around them.
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@menu
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@ -410,23 +410,17 @@ demonstrate how to code around them.
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@cindex at command
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The current implementation of mcron does not provide for an at command
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(a command-line program that allows the user to specify that a job
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runs exactly once at a certain time). This can, however, be achieved.
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runs exactly once at a certain time). This can, however, be achieved.
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Suppose the program @code{my-program} needs to be run at midnight
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tonight. A Guile script like the following should work. FIXME: TEST
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THIS EXAMPLE.
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tonight. A Guile script like the following would work (but a printed
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schedule, obtained with the @code{--schedule} option, will show
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superfluous entries).
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@example
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(define my-program-flag #t)
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(job (lambda (current-time)
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(if my-program-flag
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(begin
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(set! my-program-flag #f)
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(next-day-from current-time))
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99999999))
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(job '(next-day)
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(lambda () (system "my-program")
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(kill (getppid))))
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(kill (getppid) SIGINT)))
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@end example
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@node Every second Sunday, Two hours every day, AT commands, Extended Guile examples
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@ -434,7 +428,7 @@ THIS EXAMPLE.
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@cindex examples, every second sunday
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To run @code{my-program} on the second Sunday of every month, a Guile
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script like the following should suffice (it is left as an exercise to
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the student to understand how this works!). FIXME: TEST THIS EXAMPLE.
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the student to understand how this works!).
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@example
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(job (lambda (current-time)
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@ -442,11 +436,22 @@ the student to understand how this works!). FIXME: TEST THIS EXAMPLE.
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(first-day (tm:wday (localtime next-month)))
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(second-sunday (if (eqv? first-day 0)
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8
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(- 15 first-day))))
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(- 14 first-day))))
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(+ next-month (* 24 60 60 second-sunday))))
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"my-program")
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@end example
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@cindex daylight savings time
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Note that this example is also instructive in that it demonstrates
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mcron's indeterminacy when the clocks are adjusted for summertime; use
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the @code{-s 12} option to @code{mcron}, and see the off-by-one hour
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error that occurs twice a year. This is a known problem, that
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daylight savings time shifts are not taken into account very well. If
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things are critical, your best bet is to set your TZ environment
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variable to `:Universal', and express all your configuration files in
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Universal Coordinated Time (UTC).
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@node Two hours every day, Missing the first appointment, Every second Sunday, Extended Guile examples
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@subsection Two hours every day
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@ -461,10 +466,10 @@ effect.
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@end example
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Rather than running the my-program program at one o'clock and two
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o'clock every day, it will only run it at one o'clock. This is because
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o'clock every day, it will only run it at one o'clock. This is because
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each time mcron has to compute the next time to run the command, it
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first obtains the next day, and then finds the earliest hour in that
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day to run at. Thus, after running the command at one o'clock, the
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day to run at. Thus, after running the command at one o'clock, the
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program first skips forwards to the next midnight (missing the two
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o'clock appointment), and then finds the next one o'clock schedule.
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@ -488,7 +493,7 @@ The command
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@end example
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will run @code{my-program} every day at four o'clock in the
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afternoon. However, if mcron is started with this script at midday,
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afternoon. However, if mcron is started with this script at midday,
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the first time the command will run will be four o'clock tomorrow;
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today's appointment will be missed (one time only).
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@ -520,9 +525,9 @@ second-to-last day of every month.
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@cindex vixie definition
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@cindex vixie compatibility
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@cindex compatibility, vixie
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@emph{NOTE} that this section is definitive. If there is a difference in
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@emph{NOTE} that this section is definitive. If there is a difference in
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behaviour between the mcron program and this part of the manual, then
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there is a bug in the program. This section is also copied verbatim
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there is a bug in the program. This section is also copied verbatim
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from Paul Vixie's documentation for his cron program, and his
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copyright notice is duly reproduced below.
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@ -530,10 +535,10 @@ There are three problems with this specification.
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@cindex zero'th day of month
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@cindex 0'th day of month
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1. It is allowed to specify days of the month in the range 0-31. What
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1. It is allowed to specify days of the month in the range 0-31. What
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does it mean to specify day 0? Looking at the Vixie source code, it
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seems that if this date appears as part of a list, it has no
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effect. However, if it appears on its own, the effect is to say
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effect. However, if it appears on its own, the effect is to say
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``don't run on any particular day of the month, only take the week-day
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specification into account.'' Mcron has been coded to mimic this
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behaviour as a special case (unmodified mcron logic implies that this
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@ -542,17 +547,17 @@ previous month).
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@cindex thirteenth month of year
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@cindex 13th month of year
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2. Similarly to the above (but different), months of the year can be
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specified in the range 0-12. In the case of mcron (don't know what
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2. Similarly to the above (but different), months of the year can be
|
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specified in the range 0-12. In the case of mcron (don't know what
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Vixie cron did) month 12 will cause the program to wait until January
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of the following year (but don't rely on this).
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@cindex shell
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@cindex environment variables, shell
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@cindex /etc/passwd
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3. Somewhere it says that cron sets the SHELL environment variable to
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3. Somewhere it says that cron sets the SHELL environment variable to
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/bin/sh, and elsewhere it implies that the default behaviour is for
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the user's default shell to be used to execute commands. Mcron sets
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the user's default shell to be used to execute commands. Mcron sets
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the variable and runs the command in the user's default shell, as
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advertised by the /etc/passwd file.
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@ -624,7 +629,7 @@ trailing blanks.
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@cindex HOME environment variable
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@cindex /etc/passwd
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Several environment variables are set up automatically by the
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@code{cron} daemon. SHELL is set to /bin/sh, and LOGNAME and HOME are
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@code{cron} daemon. SHELL is set to /bin/sh, and LOGNAME and HOME are
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set from the /etc/passwd line of the crontab's owner. HOME and SHELL
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may be overridden by settings in the crontab; LOGNAME may not.
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@ -653,7 +658,7 @@ followed by a user name if this is the system crontab file,
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followed by a command. Commands are executed by @code{cron}
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when the minute, hour, and month of year fields match the current
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time, @strong{and} when at least one of the two day fields (day of month, or day of week)
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match the current time (see ``Note'' below). @code{cron} examines cron entries once every minute.
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match the current time (see ``Note'' below). @code{cron} examines cron entries once every minute.
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The time and date fields are:
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@cindex vixie time specification fields
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@ -693,7 +698,7 @@ hours'', just use ``*/2''.
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Names can also be used for the ``month'' and ``day of week''
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fields. Use the first three letters of the particular
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day or month (case doesn't matter). Ranges or
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lists of names are not allowed. @footnote{Mcron allows any alphabetic
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lists of names are not allowed. @footnote{Mcron allows any alphabetic
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characters after a name, so full names of days or months are also valid.}
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@cindex % character on vixie-style commands
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@ -785,14 +790,14 @@ either).
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@cindex crond program
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@cindex crontab program
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The program adopts one of three different personalities depending on
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the name used to invoke it. In a standard installation, the program is
|
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the name used to invoke it. In a standard installation, the program is
|
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installed in the system under the names mcron, cron and crontab
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(installed SUID).
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The recommended way to invoke the program is via the mcron personality
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described in the next section. The program can also be run as cron by
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described in the next section. The program can also be run as cron by
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root, and by the SUID program crontab by individual users to gain
|
||||
backwards compatibility with Vixie cron. However, due to the fact that
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backwards compatibility with Vixie cron. However, due to the fact that
|
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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
|
||||
unusable, hence the recommendation to use the mcron personality.
|
||||
|
|
@ -800,7 +805,7 @@ unusable, hence the recommendation to use the mcron personality.
|
|||
@cindex deprecated, vixie personality
|
||||
Furthermore, the Vixie personality is considered deprecated by this
|
||||
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
|
||||
personality will ever actually go away, but the program may in future
|
||||
be split into two distinct parts, and new developments will only take
|
||||
place in the part which implements the mcron personality.
|
||||
|
|
@ -822,17 +827,20 @@ place in the part which implements the mcron personality.
|
|||
@cindex mcron arguments
|
||||
@cindex command line, mcron
|
||||
@cindex mcron command line
|
||||
Mcron should be run by the user who wants to schedule his jobs. It may
|
||||
be made a background job using the facilities of the shell. The basic
|
||||
Mcron should be run by the user who wants to schedule his jobs. It may
|
||||
be made a background job using the facilities of the shell. The basic
|
||||
command is
|
||||
@code{mcron [OPTION ...] [file ...]}
|
||||
which has the effect of reading all the configuration files specified
|
||||
(subject to the options) and then waiting until it is time to execute
|
||||
some command. If no files are given on the command line, then mcron
|
||||
will look in the user's ~/.cron directory. In either case, files which
|
||||
some command. If no files are given on the command line, then mcron
|
||||
will look in the user's ~/.cron directory. In either case, files which
|
||||
end in the extension .vixie or .vix will be assumed to contain
|
||||
Vixie-style crontabs, and files ending .guile or .gle will be assumed
|
||||
to contain scheme code and will be executed as such.
|
||||
to contain scheme code and will be executed as 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 read them, possibly
|
||||
using the @code{stdin} option to specify the type of file.
|
||||
|
||||
The program accepts the following options.
|
||||
|
||||
|
|
@ -845,12 +853,12 @@ The program accepts the following options.
|
|||
@cindex options, -s
|
||||
@cindex -s option
|
||||
@cindex --schedule option
|
||||
With this option specified no commands are run. Instead, the program
|
||||
With this option specified no commands are run. Instead, the program
|
||||
computes the times the commands would be run and prints the
|
||||
information to the screen, and then immediately exits.
|
||||
|
||||
The count, if supplied, indicates the number of commands to
|
||||
display. The default value is 8.
|
||||
display. The default value is 8.
|
||||
|
||||
@cindex daemon option
|
||||
@cindex options, daemon
|
||||
|
|
@ -873,7 +881,7 @@ terminal and run as a daemon process.
|
|||
@itemx --stdin=(vixie|guile)
|
||||
This option is used to indicate whether the configuration information
|
||||
being passed on the standard input is in Vixie format or Guile
|
||||
format. Guile is the default.
|
||||
format. Guile is the default.
|
||||
|
||||
@cindex -v option
|
||||
@cindex --version option
|
||||
|
|
@ -903,19 +911,23 @@ standard output.
|
|||
@cindex running crond
|
||||
@cindex @CONFIG_SPOOL_DIR@
|
||||
@cindex @CONFIG_SOCKET_FILE@
|
||||
NOTE THAT THIS SECTION ONLY APPLIES IF THE @code{cron} or
|
||||
@code{crond}, and @code{crontab} PROGRAMS HAVE BEEN INSTALLED BY THE
|
||||
SYSTEM ADMINISTRATOR.
|
||||
|
||||
If the program runs by the name of @code{cron} or @code{crond}, then
|
||||
it will read all the files in @code{@CONFIG_SPOOL_DIR@} (which should only
|
||||
be readable by root) and the file @code{/etc/crontab}, and then
|
||||
detaches itself from the terminal to live forever as a daemon
|
||||
process. Additionally, it creates a UNIX socket at
|
||||
process. Additionally, it creates a UNIX socket at
|
||||
@code{@CONFIG_SOCKET_FILE@}, and listens for messages sent to that socket
|
||||
consisting of a user name whose crontabs have been changed. In this
|
||||
case, the program will re-read that user's crontab. This is for
|
||||
consisting of a user name whose crontabs have been changed. In this
|
||||
case, the program will re-read that user's crontab. This is for
|
||||
correct functioning with the crontab program.
|
||||
|
||||
Further, if the @code{--noetc} option was not used, a job is scheduled
|
||||
to run every minute to check if /etc/crontab has been modified
|
||||
recently. If so, this file will also be re-read.
|
||||
recently. If so, this file will also be re-read.
|
||||
|
||||
The options which may be used with this program are as follows.
|
||||
|
||||
|
|
@ -947,12 +959,12 @@ standard output.
|
|||
@cindex options, -s
|
||||
@cindex -s option
|
||||
@cindex --schedule option
|
||||
With this option specified no commands are run. Instead, the program
|
||||
With this option specified no commands are run. Instead, the program
|
||||
computes the times the commands would be run and prints the
|
||||
information to the screen, and then immediately exits.
|
||||
|
||||
The count, if supplied, indicates the number of commands to
|
||||
display. The default value is 8.
|
||||
display. The default value is 8.
|
||||
|
||||
@cindex -n option
|
||||
@cindex --noetc option
|
||||
|
|
@ -961,7 +973,7 @@ display. The default value is 8.
|
|||
@item -n
|
||||
@itemx --noetc
|
||||
This tells cron not to add a job to the system which wakes up every
|
||||
minute to check for modifications to @code{/etc/crontab}. It is
|
||||
minute to check for modifications to @code{/etc/crontab}. It is
|
||||
recommended that this option be used (and further that the
|
||||
@code{/etc/crontab} file be taken off the system altogether!)
|
||||
|
||||
|
|
@ -972,9 +984,9 @@ recommended that this option be used (and further that the
|
|||
@cindex crontab, invoking
|
||||
@cindex running crontab
|
||||
This program is run by individual users to inspect or modify their
|
||||
crontab files. If a change is made to the file, then the root daemon
|
||||
crontab files. If a change is made to the file, then the root daemon
|
||||
process will be given a kick, and will immediately read the new
|
||||
configuration. A warning will be issued to standard output if it
|
||||
configuration. A warning will be issued to standard output if it
|
||||
appears that a cron daemon is not running.
|
||||
|
||||
The command is used as
|
||||
|
|
@ -986,7 +998,7 @@ or
|
|||
@code{crontab [-u user] ( -l | -e | -r )}
|
||||
|
||||
Only the root user can use the -u option, to specify the manipulation
|
||||
of another user's crontab file. In the first instance, the entire
|
||||
of another user's crontab file. In the first instance, the entire
|
||||
crontab file of the user is replaced with the contents of the
|
||||
specified file, or standard input if the file is ``-''.
|
||||
|
||||
|
|
@ -1025,7 +1037,7 @@ Delete the user's crontab file, and exit.
|
|||
@item -e
|
||||
@item --edit
|
||||
Using the editor specified in the user's VISUAL or EDITOR environment
|
||||
variables, allow the user to edit his crontab. Once the user exits the
|
||||
variables, allow the user to edit his crontab. Once the user exits the
|
||||
editor, the crontab is checked for parseability, and if it is okay
|
||||
then it is installed as the user's new crontab and the daemon is
|
||||
notified that a change has taken place, so that the new file will
|
||||
|
|
@ -1064,25 +1076,25 @@ No problems.
|
|||
|
||||
@item 1
|
||||
An attempt has been made to start cron but there is already a
|
||||
@CONFIG_PID_FILE@ file. If there really is no other cron daemon
|
||||
@CONFIG_PID_FILE@ file. If there really is no other cron daemon
|
||||
running (this does not include invokations of mcron) then you should
|
||||
remove this file before attempting to run cron.
|
||||
|
||||
@item 2
|
||||
In parsing a guile configuration file, a @code{job} command has been
|
||||
seen but the second argument is neither a procedure, list or
|
||||
string. This argument is the job's action, and needs to be specified
|
||||
string. This argument is the job's action, and needs to be specified
|
||||
in one of these forms.
|
||||
|
||||
@item 3
|
||||
In parsing a guile configuration file, a @code{job} command has been
|
||||
seen but the first argument is neither a procedure, list or
|
||||
string. This argument is the job's next-time specification, and needs
|
||||
string. This argument is the job's next-time specification, and needs
|
||||
to be specified in one of these forms.
|
||||
|
||||
@item 4
|
||||
An attempt to run cron has been made by a user who does not have
|
||||
permission to access the crontabs in @CONFIG_SPOOL_DIR@. These files
|
||||
permission to access the crontabs in @CONFIG_SPOOL_DIR@. These files
|
||||
should be readable only by root, and the cron daemon must be run as
|
||||
root.
|
||||
|
||||
|
|
@ -1096,11 +1108,11 @@ the files @CONFIG_ALLOW_FILE@ and @CONFIG_DENY_FILE@.
|
|||
|
||||
@item 7
|
||||
Crontab has been run with more than one of the arguments @code{-l},
|
||||
@code{-r}, @code{-e}. These are mutually exclusive options.
|
||||
@code{-r}, @code{-e}. These are mutually exclusive options.
|
||||
|
||||
@item 8
|
||||
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
|
||||
An invalid vixie-style time specification has been supplied.
|
||||
|
|
@ -1120,12 +1132,12 @@ Either the ~/.cron directory does not exist, or there is a problem
|
|||
reading the files there.
|
||||
|
||||
@c @item 14
|
||||
@c There is a problem writing to /var/cron/update. This is probably
|
||||
@c There is a problem writing to /var/cron/update. This is probably
|
||||
@c because the crontab program is not installed SUID root, as it should
|
||||
@c be.
|
||||
|
||||
@item 15
|
||||
Crontab has been run without any arguments at all. There is no default
|
||||
Crontab has been run without any arguments at all. There is no default
|
||||
behaviour in this case.
|
||||
|
||||
@item 16
|
||||
|
|
@ -1144,13 +1156,13 @@ programs if they are linked against libguile.
|
|||
It may be, for example, that a program needs to perform house-keeping
|
||||
functions at certain times of the day, in which case it can spawn
|
||||
(either fork or thread) a sub-process which uses a built-in
|
||||
mcron. Another example may be a program which must sleep until some
|
||||
mcron. Another example may be a program which must sleep until some
|
||||
non-absolute time specified on the Gregorian calendar (the first day
|
||||
of next week, for example). Finally, it may be the wish of the user to
|
||||
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.
|
||||
|
||||
The core 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 main function. It also
|
||||
introduces the facilities for accumulating a set of environment
|
||||
modifiers, which take effect when jobs run.
|
||||
|
||||
|
|
@ -1169,16 +1181,16 @@ modifiers, which take effect when jobs run.
|
|||
@cindex modules, core
|
||||
|
||||
This module may be used by including @code{(use-modules (mcron core))}
|
||||
in a program. The main functions are @code{add-job} and
|
||||
in a program. The main functions are @code{add-job} and
|
||||
@code{run-job-loop}, which allow a program to create a list of job
|
||||
specifications to run, and then to initiate the wait-run-wait loop
|
||||
firing the jobs off at the requisite times. However, before they are
|
||||
firing the jobs off at the requisite times. However, before they are
|
||||
introduced two functions which manipulate the environment that takes
|
||||
effect when a job runs are defined.
|
||||
|
||||
@cindex environment
|
||||
The environment is a set of name-value pairs which is built up
|
||||
incrementally. Each time the @code{add-job} function is called, the
|
||||
incrementally. Each time the @code{add-job} function is called, the
|
||||
environment modifiers that have been accumulated up to that point are
|
||||
stored with the new job specification, and when the job actually runs
|
||||
these name-value pairs are used to modify the run-time environment in
|
||||
|
|
@ -1196,16 +1208,16 @@ specified so far to be forgotten.
|
|||
|
||||
@deffn{Scheme procedure} add-job time-proc action displayable configuration-time configuration-user
|
||||
This procedure adds a job specification to the list of all jobs to
|
||||
run. @var{time-proc} should be a procedure taking exactly one argument
|
||||
which will be a UNIX time. This procedure must compute the next time
|
||||
that the job should run, and return the result. @var{action} should be
|
||||
run. @var{time-proc} should be a procedure taking exactly one argument
|
||||
which will be a UNIX time. This procedure must compute the next time
|
||||
that the job should run, and return the result. @var{action} should be
|
||||
a procedure taking no arguments, and contains the instructions that
|
||||
actually get executed whenever the job is scheduled to
|
||||
run. @var{displayable} should be a string, and is only for the use of
|
||||
run. @var{displayable} should be a string, and is only for the use of
|
||||
humans; it can be anything which identifies or simply gives a clue as
|
||||
to the purpose or function of this job. @var{configuration-time} is
|
||||
to the purpose or function of this job. @var{configuration-time} is
|
||||
the time from which the first invokation of this job should be
|
||||
computed. Finally, @var{configuration-user} should be the passwd entry
|
||||
computed. Finally, @var{configuration-user} should be the passwd entry
|
||||
for the user under whose personality the job is to run.
|
||||
@end deffn
|
||||
|
||||
|
|
@ -1215,9 +1227,9 @@ for the user under whose personality the job is to run.
|
|||
This procedure returns only under exceptional circumstances, but
|
||||
usually loops forever waiting for the next time to arrive when a job
|
||||
needs to run, running that job, recomputing the next run time, and
|
||||
then waiting again. However, the wait can be interrupted by data
|
||||
then waiting again. However, the wait can be interrupted by data
|
||||
becoming available for reading on one of the file descriptors in the
|
||||
fd-list, if supplied. Only in this case will the procedure return to
|
||||
fd-list, if supplied. Only in this case will the procedure return to
|
||||
the calling program, which may then make modifications to the job list
|
||||
before calling the @code{run-job-loop} procedure again to resume execution of
|
||||
the mcron core.
|
||||
|
|
@ -1227,17 +1239,17 @@ the mcron core.
|
|||
|
||||
The argument @var{user} should be a string naming a user (his
|
||||
login name), or an integer UID, or an object representing the user's passwd
|
||||
entry. All jobs on the current job list that are scheduled to be run
|
||||
entry. All jobs on the current job list that are scheduled to be run
|
||||
under this personality are removed from the job list.
|
||||
@end deffn
|
||||
|
||||
@deffn{Scheme procedure} get-schedule count
|
||||
@cindex schedule of jobs
|
||||
The argument @var{count} should be an integer value giving the number
|
||||
of time-points in the future to report that jobs will run as. Note
|
||||
of time-points in the future to report that jobs will run as. Note
|
||||
that this procedure is disruptive; if @code{run-job-loop} is called
|
||||
after this procedure, the first job to run will be the one after the
|
||||
last job that was reported in the schedule report. The report itself
|
||||
last job that was reported in the schedule report. The report itself
|
||||
is returned to the calling program as a string.
|
||||
@end deffn
|
||||
|
||||
|
|
@ -1250,7 +1262,7 @@ This module is introduced to a program with the command
|
|||
@code{(use-modules (mcron redirect))}.
|
||||
|
||||
This module provides the @code{with-mail-out} function, described
|
||||
fully in @ref{Guile Syntax}.
|
||||
fully in @ref{Guile Syntax}.
|
||||
|
||||
@node The vixie-time module, The job-specifier module, The redirect module, Guile modules
|
||||
@section The vixie-time module
|
||||
|
|
@ -1263,7 +1275,7 @@ vixie-time))}.
|
|||
This module provides a single method for converting a vixie-style time
|
||||
specification into a procedure which can be used as the
|
||||
@code{next-time-function} to the core @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}
|
||||
for full details of the allowed format for the time string.
|
||||
|
||||
@deffn{Scheme procedure} parse-vixie-time time-string
|
||||
|
|
@ -1287,7 +1299,7 @@ configuration files, namely @code{range}, @code{next-year-from},
|
|||
@code{next-day-from}, @code{next-day}, @code{next-hour-from},
|
||||
@code{next-hour}, @code{next-minute-from}, @code{next-minute},
|
||||
@code{next-second-from}, @code{next-second},
|
||||
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.
|
||||
|
||||
Once this module is loaded, a scheme configuration file can be used to
|
||||
|
|
@ -1320,7 +1332,7 @@ as the optional argument.
|
|||
@deffn{Scheme procedure} read-vixie-file name . parse-line
|
||||
|
||||
This procedure attempts to open the named file, and if it fails will
|
||||
return silently. Otherwise, the behaviour is identical to
|
||||
return silently. Otherwise, the behaviour is identical to
|
||||
@code{read-vixie-port} above.
|
||||
|
||||
@end deffn
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue