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zshcalsys (1)

Name

zshcalsys - zsh calendar system

Synopsis

Please see following description for synopsis

Description

ZSHCALSYS(1)                General Commands Manual               ZSHCALSYS(1)



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  immi-
       nent or future events, details of which are stored in a text file (typ-
       ically 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 mod-
       ule 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 for-
       mat 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 infor-
       mation.  This can be used to hide information useful  to  the  calendar
       system  but not to the user, such as the unique identifier used by cal-
       endar_add.

       The Emacs extension that a date with no description may refer to a num-
       ber 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 with-
       out 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  insensi-
       tive,  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.

       o      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.

       o      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:

       o      HH:MM[:SS[.FFFFF]] [am|pm|a.m.|p.m.]

       o      HH:MM.SS[.FFFFF] [am|pm|a.m.|p.m.]

       Here,  square brackets indicate optional elements, possibly with alter-
       natives.  Fractions of a second are recognised but ignored.  For  abso-
       lute 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:

       o      YYYY/MM/DD

       o      YYYY-MM-DD

       o      YYYY/MNM/DD

       o      YYYY-MNM-DD

       o      DD[th|st|rd] MNM[,] [ YYYY ]

       o      MNM DD[th|st|rd][,] [ YYYY ]

       o      DD[th|st|rd]/MM[,] YYYY

       o      DD[th|st|rd]/MM/YYYY

       o      MM/DD[th|st|rd][,] YYYY

       o      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 sep-
       arators  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 yester-
       day, today and tomorrow are handled.  All matches are case-insensitive.
       Hence  if today is Monday, then Sunday is equivalent to yesterday, Mon-
       day 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 argu-
       ment to calendar_scandate directly provides an anchor for relative cal-
       culations.

       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 specifica-
       tion 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 con-
       tinuation 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 associ-
       ated  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  effec-
              tively this shows all events before the given date.

              end may start with a +, in which case the remainder of the spec-
              ification 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 cal-
                     endar 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  inter-
                     active  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  rel-
                     date 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 cer-
                     tain recurrences of an  event  are  rescheduled  or  can-
                     celled.   This  is done with the OCCURRENCE keyword, fol-
                     lowed by whitespace and the date and time of  the  occur-
                     rence 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 recur-
                     rence) 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 iden-
                     tify 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  con-
                     tinuation  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 process-
                     ing.  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  sec-
              tion  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  calen-
              dar_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  calen-
              dar  -s  above.   To  reschedule or cancel a single event calen-
              dar_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 can-
              celled 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  edi-
              tor as soon as possible.

       calendar_parse calendar-entry
              This  is the internal function that analyses the parts of a cal-
              endar entry, which is passed as the only argument.  The function
              returns status 1 if the argument could not be parsed as a calen-
              dar 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 regu-
                     lar 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 key-
                     word 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, calen-
              dar_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 specifi-
              cations,  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 sup-
              plied 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 rel-
              ative 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  con-
              tains 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  argu-
              ment  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  con-
              sulted.   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 zshmod-
       ules(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 exten-
              sions 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  cal-
              endar file, and in calendar_showdate as the final output format.

              If  the  style is not set, the default used is similar the stan-
              dard 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  argu-
                     ment;  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  rela-
                     tive  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 com-
              mand 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  sup-
       port  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 vari-
       able number of days.

       The  calendar_show  function is currently hardwired to use xmessage for
       displaying alerts on X Window System displays.  This should be  config-
       urable 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.



zsh 5.6.2                     September 14, 2018                  ZSHCALSYS(1)