NAME
zshcalsys - zsh calendar systemDESCRIPTION
The shell is supplied with a series of functions to replace and enhance the traditional Unix calendar programme, which warns the user of imminent or future events, details of which are stored in a text file (typically calendar in the user's home directory). The version provided here includes a mechanism for alerting the user when an event is due. In addition functions age, before and after are provided that can be used in a glob qualifier; they allow files to be selected based on their modification times. The format of the calendar file and the dates used there in and in the age function are described first, then the functions that can be called to examine and modify the calendar file. The functions here depend on the availability of the zsh/datetime module which is usually installed with the shell. The library function strptime() must be available; it is present on most recent operating systems.FILE AND DATE FORMATS
Calendar File Format
The calendar file is by default ~/calendar. This can be configured by the calendar-file style, see the section STYLES below. The basic format consists of a series of separate lines, with no indentation, each including a date and time specification followed by a description of the event. Various enhancements to this format are supported, based on the syntax of Emacs calendar mode. An indented line indicates a continuation line that continues the description of the event from the preceding line (note the date may not be continued in this way). An initial ampersand ( &) is ignored for compatibility. An indented line on which the first non-whitespace character is # is not displayed with the calendar entry, but is still scanned for information. This can be used to hide information useful to the calendar system but not to the user, such as the unique identifier used by calendar_add. The Emacs extension that a date with no description may refer to a number of succeeding events at different times is not supported. Unless the done-file style has been altered, any events which have been processed are appended to the file with the same name as the calendar file with the suffix .done, hence ~/calendar.done by default. An example is shown below.Date Format
The format of the date and time is designed to allow flexibility without admitting ambiguity. (The words `date' and `time' are both used in the documentation below; except where specifically noted this implies a string that may include both a date and a time specification.) Note that there is no localization support; month and day names must be in English and separator characters are fixed. Matching is case insensitive, and only the first three letters of the names are significant, although as a special case a form beginning "month" does not match "Monday". Furthermore, time zones are not handled; all times are assumed to be local. It is recommended that, rather than exploring the intricacies of the system, users find a date format that is natural to them and stick to it. This will avoid unexpected effects. Various key facts should be noted.- •
- In particular, note the confusion between month/ day/year and day/month/year when the month is numeric; these formats should be avoided if at all possible. Many alternatives are available.
- •
- The year must be given in full to avoid confusion, and only years from 1900 to 2099 inclusive are matched.
2007/04/03 13:13 2007/04/03:13:13 2007/04/03 1:13 pm 3rd April 2007, 13:13 April 3rd 2007 1:13 p.m. Apr 3, 2007 13:13 Tue Apr 03 13:13:00 2007 13:13 2007/apr/3
- •
- HH:MM[:SS[.FFFFF]] [ am|pm|a.m.|p.m.]
- •
- HH:MM.SS[.FFFFF] [ am|pm|a.m.|p.m.]
+0100 GMT GMT-7 CET+1CDT
- •
- YYYY/MM/DD
- •
- YYYY-MM-DD
- •
- YYYY/MNM/DD
- •
- YYYY-MNM-DD
- •
- DD[th|st|rd] MNM[,] [ YYYY ]
- •
- MNM DD[th|st|rd][,] [ YYYY ]
- •
- DD[th|st|rd]/MM[,] YYYY
- •
- DD[th|st|rd]/MM/YYYY
- •
- MM/DD[th|st|rd][,] YYYY
- •
- MM/DD[th|st|rd]/YYYY
Fri Aug 18 17:00:48 BST 2006
Fri Aug 18 2006
Relative Time Format
In certain places relative times are handled. Here, a date is not allowed; instead a combination of various supported periods are allowed, together with an optional time. The periods must be in order from most to least significant. In some cases, a more accurate calculation is possible when there is an anchor date: offsets of months or years pick the correct day, rather than being rounded, and it is possible to pick a particular day in a month as `(1st Friday)', etc., as described in more detail below. Anchors are available in the following cases. If one or two times are passed to the function calendar, the start time acts an anchor for the end time when the end time is relative (even if the start time is implicit). When examining calendar files, the scheduled event being examined anchors the warning time when it is given explicitly by means of the WARN keyword; likewise, the scheduled event anchors a repetition period when given by the RPT keyword, so that specifications such as RPT 2 months, 3rd Thursday are handled properly. Finally, the -R argument to calendar_scandate directly provides an anchor for relative calculations. The periods handled, with possible abbreviations are:- Years
- years, yrs, ys, year, yr, y, yearly. A year is 365.25 days unless there is an anchor.
- Months
- months, mons, mnths, mths, month, mon, mnth, mth, monthly. Note that m, ms, mn, mns are ambiguous and are not handled. A month is a period of 30 days rather than a calendar month unless there is an anchor.
- Weeks
- weeks, wks, ws, week, wk, w, weekly
- Days
- days, dys, ds, day, dy, d, daily
- Hours
- hours, hrs, hs, hour, hr, h, hourly
- Minutes
- minutes, mins, minute, min, but not m, ms, mn or mns
- Seconds
- seconds, secs, ss, second, sec, s
30 years 3 months 4 days 3:42:41 14 days 5 hours Monthly, 3rd Thursday 4d,10hr
Example
Here is an example calendar file. It uses a consistent date format, as recommended above.Feb 1, 2006 14:30 Pointless bureaucratic meeting Mar 27, 2006 11:00 Mutual recrimination and finger pointing Bring water pistol and waterproofs Mar 31, 2006 14:00 Very serious managerial pontification # UID 12C7878A9A50 Apr 10, 2006 13:30 Even more pointless blame assignment exercise WARN 30 mins May 18, 2006 16:00 Regular moaning session RPT monthly, 3rd Thursday
USER FUNCTIONS
This section describes functions that are designed to be called directly by the user. The first part describes those functions associated with the user's calendar; the second part describes the use in glob qualifiers.Calendar system functions
- calendar [ -abdDsv ] [ -C calfile ] [ -n num ] [ -S showprog ]
- [ [ start ] end ]
- calendar -r [ -abdDrsv ] [ -C calfile ] [ -n num ] [ -S showprog ]
- [ start ]
- Show events in the calendar.
With no arguments, show events from the start of today until the end of the next
working day after today. In other words, if today is Friday, Saturday, or
Sunday, show up to the end of the following Monday, otherwise show today and
tomorrow.
If end is given, show events from the start of today up to the time and
date given, which is in the format described in the previous section. Note
that if this is a date the time is assumed to be midnight at the start of the
date, so that effectively this shows all events before the given date.
end may start with a +, in which case the remainder of the
specification is a relative time format as described in the previous section
indicating the range of time from the start time that is to be included.
If start is also given, show events starting from that time and date. The
word now can be used to indicate the current time.
To implement an alert when events are due, include calendar -s in your
~/.zshrc file.
Options:
- -a
- Show all items in the calendar, regardless of the start and end.
- -b
- Brief: don't display continuation lines (i.e. indented lines following the line with the date/time), just the first line.
- -B lines
- Brief: display at most the first lines lines of the calendar entry. ` -B 1' is equivalent to `-b'.
- -C calfile
- Explicitly specify a calendar file instead of the value of the calendar-file style or the default ~/calendar.
- -d
- Move any events that have passed from the calendar file to the "done" file, as given by the done-file style or the default which is the calendar file with .done appended. This option is implied by the -s option.
- -D
- Turns off the option -d, even if the -s option is also present.
- -n num, -num
- Show at least num events, if present in the calendar file, regardless of the start and end.
- -r
- Show all the remaining options in the calendar, ignoring the given end time. The start time is respected; any argument given is treated as a start time.
- -s
- Use the shell's sched command to schedule a timed event that will warn the user when an event is due. Note that the sched command only runs if the shell is at an interactive prompt; a foreground task blocks the scheduled task from running until it is finished.
The timed event usually runs the programme calendar_show to show the
event, as described in the section UTILITY FUNCTIONS below.
By default, a warning of the event is shown five minutes before it is due. The
warning period can be configured by the style warn-time or for a single
calendar entry by including WARN reltime in the first line of
the entry, where reltime is one of the usual relative time formats.
A repeated event may be indicated by including RPT reldate in the
first line of the entry. After the scheduled event has been displayed it will
be re-entered into the calendar file at a time reldate after the
existing event. Note that this is currently the only use made of the repeat
count, so that it is not possible to query the schedule for a recurrence of an
event in the calendar until the previous event has passed.
If RPT is used, it is also possible to specify that certain recurrences
of an event are rescheduled or cancelled. This is done with the
OCCURRENCE keyword, followed by whitespace and the date and time of the
occurrence in the regular sequence, followed by whitespace and either the date
and time of the rescheduled event or the exact string CANCELLED. In
this case the date and time must be in exactly the "date with local
time" format used by the text/calendar MIME type (RFC 2445),
<YYYY><MM><DD>
T<hh><mm><ss> (note the presence of the
literal character T). The first word (the regular recurrence) may be
something other than a proper date/time to indicate that the event is
additional to the normal sequence; a convention that retains the formatting
appearance is XXXXXXXXTXXXXXX.
Furthermore, it is useful to record the next regular recurrence (as then the
displayed date may be for a rescheduled event so cannot be used for
calculating the regular sequence). This is specified by RECURRENCE and
a time or date in the same format. calendar_add adds such an indication
when it encounters a recurring event that does not include one, based on the
headline date/time.
If calendar_add is used to update occurrences the UID keyword
described there should be present in both the existing entry and the added
occurrence in order to identify recurring event sequences.
For example,
The event that occurs at 11:00 on 13th May 2010 is rescheduled an hour later.
The event that occurs a week later is cancelled. The occurrences are given on
a continuation line starting with a # character so will not usually be
displayed as part of the event. As elsewhere, no account of time zones is
taken with the times. After the next event occurs the headline date/time will
be ` Thu May 13, 2010 12:00' while the RECURRENCE date/time will
be ` 20100513T110000' (note that cancelled and moved events are not
taken account of in the RECURRENCE, which records what the next regular
recurrence is, but they are accounted for in the headline date/time).
It is safe to run calendar -s to reschedule an existing event (if the
calendar file has changed, for example), and also to have it running in
multiples instances of the shell since the calendar file is locked when in
use.
By default, expired events are moved to the "done" file; see the
-d option. Use -D to prevent this.
Thu May 6, 2010 11:00 Informal chat RPT 1 week # RECURRENCE 20100506T110000 # OCCURRENCE 20100513T110000 20100513T120000 # OCCURRENCE 20100520T110000 CANCELLED
- -S showprog
- Explicitly specify a programme to be used for showing events instead of the value of the show-prog style or the default calendar_show.
- -v
- Verbose: show more information about stages of processing. This is useful for confirming that the function has successfully parsed the dates in the calendar file.
- calendar_add [ -BL ] event ...
- Adds a single event to the calendar in the appropriate location. The event can contain multiple lines, as described in the section `Calendar File Format' above. Using this function ensures that the calendar file is sorted in date and time order. It also makes special arrangements for locking the file while it is altered. The old calendar is left in a file with the suffix .old.
The option -B indicates that backing up the calendar file will be handled
by the caller and should not be performed by calendar_add. The option
-L indicates that calendar_add does not need to lock the
calendar file as it is already locked. These options will not usually be
needed by users.
If the style reformat-date is true, the date and time of the new entry
will be rewritten into the standard date format: see the descriptions of this
style and the style date-format.
The function can use a unique identifier stored with each event to ensure that
updates to existing events are treated correctly. The entry should contain the
word UID, followed by whitespace, followed by a word consisting
entirely of hexadecimal digits of arbitrary length (all digits are
significant, including leading zeroes). As the UID is not directly useful to
the user, it is convenient to hide it on an indented continuation line
starting with a #, for example:
The second line will not be shown by the calendar function.
It is possible to specify the RPT keyword followed by CANCELLED
instead of a relative time. This causes any matched event or series of events
to be cancelled (the original event does not have to be marked as recurring in
order to be cancelled by this method). A UID is required in order to
match an existing event in the calendar.
calendar_add will attempt to manage recurrences and occurrences of
repeating events as described for event scheduling by calendar -s
above. To reschedule or cancel a single event calendar_add should be
called with an entry that includes the correct UID but does not
include the RPT keyword as this is taken to mean the entry applies to a
series of repeating events and hence replaces all existing information. Each
rescheduled or cancelled occurrence must have an OCCURRENCE keyword in
the entry passed to calendar_add which will be merged into the calendar
file. Any existing reference to the occurrence is replaced. An occurrence that
does not refer to a valid existing event is added as a one-off occurrence to
the same calendar entry.
Aug 31, 2007 09:30 Celebrate the end of the holidays # UID 045B78A0
- calendar_edit
- This calls the user's editor to edit the calendar file. If there are arguments, they are taken as the editor to use (the file name is appended to the commands); otherwise, the editor is given by the variable VISUAL, if set, else the variable EDITOR.
If the calendar scheduler was running, then after editing the file calendar
-s is called to update it.
This function locks out the calendar system during the edit. Hence it should be
used to edit the calendar file if there is any possibility of a calendar event
occurring meanwhile. Note this can lead to another shell with calendar
functions enabled hanging waiting for a lock, so it is necessary to quit the
editor as soon as possible.
- calendar_parse calendar-entry
- This is the internal function that analyses the parts of a calendar entry, which is passed as the only argument. The function returns status 1 if the argument could not be parsed as a calendar entry and status 2 if the wrong number of arguments were passed; it also sets the parameter reply to an empty associative array. Otherwise, it returns status 0 and sets elements of the associative array reply as follows:
- time
- The time as a string of digits in the same units as $EPOCHSECONDS
- schedtime
- The regularly scheduled time. This may differ from the actual event time time if this is a recurring event and the next occurrence has been rescheduled. Then time gives the actual time and schedtime the time of the regular recurrence before modification.
- text1
- The text from the line not including the date and time of the event, but including any WARN or RPT keywords and values.
- warntime
- Any warning time given by the WARN keyword as a string of digits containing the time at which to warn in the same units as $EPOCHSECONDS. (Note this is an absolute time, not the relative time passed down.) Not set no WARN keyword and value were matched.
- warnstr
- The raw string matched after the WARN keyword, else unset.
- rpttime
- Any recurrence time given by the RPT keyword as a string of digits containing the time of the recurrence in the same units as $EPOCHSECONDS. (Note this is an absolute time.) Not set if no RPT keyword and value were matched.
- schedrpttime
- The next regularly scheduled occurrence of a recurring event before modification. This may differ from rpttime, which is the actual time of the event that may have been rescheduled from the regular time.
- rptstr
- The raw string matched after the RPT keyword, else unset.
- text2
- The text from the line after removal of the date and any keywords and values.
- calendar_showdate [ -r ] [ -f fmt ] date-spec ...
- The given date-spec is interpreted and the corresponding date and time printed. If the initial date-spec begins with a + or - it is treated as relative to the current time; date-specs after the first are treated as relative to the date calculated so far and a leading + is optional in that case. This allows one to use the system as a date calculator. For example, calendar_showdate '+1 month, 1st Friday' shows the date of the first Friday of next month.
With the option -r nothing is printed but the value of the date and time
in seconds since the epoch is stored in the parameter REPLY.
With the option -f fmt the given date/time conversion format is
passed to strftime; see notes on the date-format style below.
In order to avoid ambiguity with negative relative date specifications, options
must occur in separate words; in other words, -r and -f should
not be combined in the same word.
- calendar_sort
- Sorts the calendar file into date and time order. The old calendar is left in a file with the suffix .old.
Glob qualifiers
- age
- The function age can be autoloaded and use separately from the calendar system, although it uses the function calendar_scandate for date formatting. It requires the zsh/stat builtin, but uses only the builtin zstat.
age selects files having a given modification time for use as a glob
qualifier. The format of the date is the same as that understood by the
calendar system, described in the section FILE AND DATE FORMATS above.
The function can take one or two arguments, which can be supplied either
directly as command or arguments, or separately as shell parameters.
The example above matches all files modified between the start of those dates.
The second argument may alternatively be a relative time introduced by a
+:
The example above is equivalent to the previous example.
In addition to the special use of days of the week, today and
yesterday, times with no date may be specified; these apply to today.
Obviously such uses become problematic around midnight.
The example above shows files modified between 12:00 and 13:00 today.
The example above matches all files modified on that date. If the second
argument is omitted it is taken to be exactly 24 hours after the first
argument (even if the first argument contains a time).
The example above supplies times. Note that whitespace within the time and date
specification must be quoted to ensure age receives the correct
arguments, hence the use of the additional colon to separate the date and
time.
This shows the same example before using another form of argument passing. The
dates and times in the parameters AGEREF and AGEREF2 stay in
effect until unset, but will be overridden if any argument is passed as an
explicit argument to age. Any explicit argument causes both parameters to be
ignored.
Instead of an explicit date and time, it's possible to use the modification time
of a file as the date and time for either argument by introducing the file
name with a colon:
matches all files created on the same day (24 hours starting from midnight) as
file1.
matches all files modified no earlier than file1 and no later than
file2; precision here is to the nearest second.
print *(e:age 2006/10/04 2006/10/09:)
print *(e:age 2006/10/04 +5d:)
print *(e-age 12:00 13:30-)
print *(e:age 2006/10/04:)
print *(e-age 2006/10/04:10:15 2006/10/04:10:45-)
AGEREF=2006/10/04:10:15 AGEREF2=2006/10/04:10:45 print *(+age)
print *(e-age :file1-)
print *(e-age :file1 :file2-)
- after
- before
- The functions after and before are simpler versions of age that take just one argument. The argument is parsed similarly to an argument of age; if it is not given the variable AGEREF is consulted. As the names of the functions suggest, a file matches if its modification time is after or before the time and date specified. If a time only is given the date is today.
The two following examples are therefore equivalent:
print *(e-after 12:00-) print *(e-after today:12:00-)
STYLES
The zsh style mechanism using the zstyle command is describe in zshmodules(1). This is the same mechanism used in the completion system. The styles below are all examined in the context :datetime:function :, for example :datetime:calendar:.- calendar-file
- The location of the main calendar. The default is ~/calendar.
- date-format
- A strftime format string (see strftime(3)) with the zsh extensions providing various numbers with no leading zero or space if the number is a single digit as described for the %D{string } prompt format in the section EXPANSION OF PROMPT SEQUENCES in zshmisc(1).
This is used for outputting dates in calendar, both to support the
-v option and when adding recurring events back to the calendar file,
and in calendar_showdate as the final output format.
If the style is not set, the default used is similar the standard system format
as output by the date command (also known as `ctime format'): ` %a
%b %d %H:%M:%S %Z %Y'.
- done-file
- The location of the file to which events which have passed are appended. The default is the calendar file location with the suffix .done. The style may be set to an empty string in which case a "done" file will not be maintained.
- reformat-date
- Boolean, used by calendar_add. If it is true, the date and time of new entries added to the calendar will be reformatted to the format given by the style date-format or its default. Only the date and time of the event itself is reformatted; any subsidiary dates and times such as those associated with repeat and warning times are left alone.
- show-prog
- The programme run by calendar for showing events. It will be passed the start time and stop time of the events requested in seconds since the epoch followed by the event text. Note that calendar -s uses a start time and stop time equal to one another to indicate alerts for specific events.
The default is the function calendar_show.
- warn-time
- The time before an event at which a warning will be displayed, if the first line of the event does not include the text EVENT reltime. The default is 5 minutes.
UTILITY FUNCTIONS
- calendar_lockfiles
- Attempt to lock the files given in the argument. To prevent problems with network file locking this is done in an ad hoc fashion by attempting to create a symbolic link to the file with the name file.lockfile. No other system level functions are used for locking, i.e. the file can be accessed and modified by any utility that does not use this mechanism. In particular, the user is not prevented from editing the calendar file at the same time unless calendar_edit is used.
Three attempts are made to lock the file before giving up. If the module
zsh/zselect is available, the times of the attempts are jittered so
that multiple instances of the calling function are unlikely to retry at the
same time.
The files locked are appended to the array lockfiles, which should be
local to the caller.
If all files were successfully locked, status zero is returned, else status one.
This function may be used as a general file locking function, although this will
only work if only this mechanism is used to lock files.
- calendar_read
- This is a backend used by various other functions to parse the calendar file, which is passed as the only argument. The array calendar_entries is set to the list of events in the file; no pruning is done except that ampersands are removed from the start of the line. Each entry may contain multiple lines.
- calendar_scandate
- This is a generic function to parse dates and times that may be used separately from the calendar system. The argument is a date or time specification as described in the section FILE AND DATE FORMATS above. The parameter REPLY is set to the number of seconds since the epoch corresponding to that date or time. By default, the date and time may occur anywhere within the given argument.
Returns status zero if the date and time were successfully parsed, else one.
Options:
- -a
- The date and time are anchored to the start of the argument; they will not be matched if there is preceding text.
- -A
- The date and time are anchored to both the start and end of the argument; they will not be matched if the is any other text in the argument.
- -d
- Enable additional debugging output.
- -m
- Minus. When -R anchor_time is also given the relative time is calculated backwards from anchor_time.
- -r
- The argument passed is to be parsed as a relative time.
- -R anchor_time
- The argument passed is to be parsed as a relative time. The time is relative to anchor_time, a time in seconds since the epoch, and the returned value is the absolute time corresponding to advancing anchor_time by the relative time given. This allows lengths of months to be correctly taken into account. If the final day does not exist in the given month, the last day of the final month is given. For example, if the anchor time is during 31st January 2007 and the relative time is 1 month, the final time is the same time of day during 28th February 2007.
- -s
- In addition to setting REPLY, set REPLY2 to the remainder of the argument after the date and time have been stripped. This is empty if the option -A was given.
- -t
- Allow a time with no date specification. The date is assumed to be today. The behaviour is unspecified if the iron tongue of midnight is tolling twelve.
- calendar_show
- The function used by default to display events. It accepts a start time and end time for events, both in epoch seconds, and an event description.
The event is always printed to standard output. If the command line editor is
active (which will usually be the case) the command line will be redisplayed
after the output.
If the parameter DISPLAY is set and the start and end times are the same
(indicating a scheduled event), the function uses the command xmessage
to display a window with the event details.
BUGS
As the system is based entirely on shell functions (with a little support from the zsh/datetime module) the mechanisms used are not as robust as those provided by a dedicated calendar utility. Consequently the user should not rely on the shell for vital alerts. There is no calendar_delete function. There is no localization support for dates and times, nor any support for the use of time zones. Relative periods of months and years do not take into account the variable number of days. The calendar_show function is currently hardwired to use xmessage for displaying alerts on X Window System displays. This should be configurable and ideally integrate better with the desktop. calendar_lockfiles hangs the shell while waiting for a lock on a file. If called from a scheduled task, it should instead reschedule the event that caused it.May 14, 2022 | zsh 5.9 |