Provided by: zsh-common_5.9-1_all 
NAME
zshcalsys - zsh calendar system
DESCRIPTION
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.
The following give some obvious examples; users finding here a format they like and not
subject to vagaries of style may skip the full description. As dates and times are
matched separately (even though the time may be embedded in the date), any date format may
be mixed with any format for the time of day provide the separators are clear (whitespace,
colons, commas).
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
More detailed rules follow.
Times are parsed and extracted before dates. They must use colons to separate hours and
minutes, though a dot is allowed before seconds if they are present. This limits time
formats to the following:
• HH:MM[:SS[.FFFFF]] [am|pm|a.m.|p.m.]
• HH:MM.SS[.FFFFF] [am|pm|a.m.|p.m.]
Here, square brackets indicate optional elements, possibly with alternatives. Fractions
of a second are recognised but ignored. For absolute times (the normal format require by
the calendar file and the age, before and after functions) a date is mandatory but a time
of day is not; the time returned is at the start of the date. One variation is allowed:
if a.m. or p.m. or one of their variants is present, an hour without a minute is allowed,
e.g. 3 p.m..
Time zones are not handled, though if one is matched following a time specification it
will be removed to allow a surrounding date to be parsed. This only happens if the format
of the timezone is not too unusual. The following are examples of forms that are
understood:
+0100
GMT
GMT-7
CET+1CDT
Any part of the timezone that is not numeric must have exactly three capital letters in
the name.
Dates suffer from the ambiguity between DD/MM/YYYY and MM/DD/YYYY. It is recommended this
form is avoided with purely numeric dates, but use of ordinals, eg. 3rd/04/2007, will
resolve the ambiguity as the ordinal is always parsed as the day of the month. Years must
be four digits (and the first two must be 19 or 20); 03/04/08 is not recognised. Other
numbers may have leading zeroes, but they are not required. The following are handled:
• 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
Here, MNM is at least the first three letters of a month name, matched case-insensitively.
The remainder of the month name may appear but its contents are irrelevant, so janissary,
febrile, martial, apricot, maybe, junta, etc. are happily handled.
Where the year is shown as optional, the current year is assumed. There are only two such
cases, the form Jun 20 or 14 September (the only two commonly occurring forms, apart from
a "the" in some forms of English, which isn't currently supported). Such dates will of
course become ambiguous in the future, so should ideally be avoided.
Times may follow dates with a colon, e.g. 1965/07/12:09:45; this is in order to provide a
format with no whitespace. A comma and whitespace are allowed, e.g. 1965/07/12, 09:45.
Currently the order of these separators is not checked, so illogical formats such as
1965/07/12, : ,09:45 will also be matched. For simplicity such variations are not shown
in the list above. Otherwise, a time is only recognised as being associated with a date
if there is only whitespace in between, or if the time was embedded in the date.
Days of the week are not normally scanned, but will be ignored if they occur at the start
of the date pattern only. However, in contexts where it is useful to specify dates
relative to today, days of the week with no other date specification may be given. The
day is assumed to be either today or within the past week. Likewise, the words yesterday,
today and tomorrow are handled. All matches are case-insensitive. Hence if today is
Monday, then Sunday is equivalent to yesterday, Monday is equivalent to today, but Tuesday
gives a date six days ago. This is not generally useful within the calendar file. Dates
in this format may be combined with a time specification; for example Tomorrow, 8 p.m..
For example, the standard date format:
Fri Aug 18 17:00:48 BST 2006
is handled by matching HH:MM:SS and removing it together with the matched (but unused)
time zone. This leaves the following:
Fri Aug 18 2006
Fri is ignored and the rest is matched according to the standard rules.
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
Spaces between the numbers are optional, but are required between items, although a comma
may be used (with or without spaces).
The forms yearly to hourly allow the number to be omitted; it is assumed to be 1. For
example, 1 d and daily are equivalent. Note that using those forms with plurals is
confusing; 2 yearly is the same as 2 years, not twice yearly, so it is recommended they
only be used without numbers.
When an anchor time is present, there is an extension to handle regular events in the form
of the nth someday of the month. Such a specification must occur immediately after any
year and month specification, but before any time of day, and must be in the form
n(th|st|rd) day, for example 1st Tuesday or 3rd Monday. As in other places, days are
matched case insensitively, must be in English, and only the first three letters are
significant except that a form beginning `month' does not match `Monday'. No attempt is
made to sanitize the resulting date; attempts to squeeze too many occurrences into a month
will push the day into the next month (but in the obvious fashion, retaining the correct
day of the week).
Here are some examples:
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
The second entry has a continuation line. The third entry has a continuation line that
will not be shown when the entry is displayed, but the unique identifier will be used by
the calendar_add function when updating the event. The fourth entry will produce a
warning 30 minutes before the event (to allow you to equip yourself appropriately). The
fifth entry repeats after a month on the 3rd Thursday, i.e. June 15, 2006, at the same
time.
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,
Thu May 6, 2010 11:00 Informal chat RPT 1 week
# RECURRENCE 20100506T110000
# OCCURRENCE 20100513T110000 20100513T120000
# OCCURRENCE 20100520T110000 CANCELLED
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.
-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:
Aug 31, 2007 09:30 Celebrate the end of the holidays
# UID 045B78A0
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.
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.
print *(e:age 2006/10/04 2006/10/09:)
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 +:
print *(e:age 2006/10/04 +5d:)
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.
print *(e-age 12:00 13:30-)
The example above shows files modified between 12:00 and 13:00 today.
print *(e:age 2006/10/04:)
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).
print *(e-age 2006/10/04:10:15 2006/10/04:10:45-)
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.
AGEREF=2006/10/04:10:15
AGEREF2=2006/10/04:10:45
print *(+age)
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:
print *(e-age :file1-)
matches all files created on the same day (24 hours starting from midnight) as
file1.
print *(e-age :file1 :file2-)
matches all files modified no earlier than file1 and no later than file2; precision
here is to the nearest second.
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.