Provided by: imapfilter_2.6.12-1_amd64 bug

NAME

     imapfilter_config — imapfilter configuration file

SYNOPSIS

     $HOME/.imapfilter/config.lua

DESCRIPTION

     imapfilter(1) uses the Lua programming language as a configuration and extension language,
     therefore the configuration file is a Lua script.

     Although knowledge of Lua is not required to use imapfilter(1), it is nonetheless
     recommended, especially if one wants to extend it.  For more information on Lua see
     http://www.lua.org/docs.html.

CONVENTIONS

     A brief description of the Lua values and types mentioned hereafter in the manual page
     follows:

         The nil is the type of the value “nil”, whose main property is to be different from any
         other value; usually it represents the absence of a useful value.

         The boolean is the type of the values “true” and “false”.  Both “nil” and “false” make a
         condition false; any other value makes it true.

         The type number represents real numbers.

         The type string represents a sequence of characters and can be defined using single
         quotes, double quotes or double square brackets.

         The type table implements associative arrays, that is, arrays that can be indexed not
         only with numbers, but with any value.

         A function is a first-class value; it can be stored in variables, passed as argument to
         other functions, and returned as a result.

OPTIONS

     Program's options are set using an already initialised table named “options”, in the
     following manner:

         options.timeout = 120
         options.namespace = false
         options.charset = 'ISO-8859-1'

     Available options are:

     cache   When this option is enabled, parts of messages are cached locally in memory to avoid
             being downloaded more than once.  The cache is preserved for the current session
             only. This variable takes a boolean as a value. Default is “true”.

     certificates
             When this option is enabled, the server certificate can be accepted and stored, in
             order to validate the authenticity of the server in future connections. This
             variable takes a boolean as a value. Default is “true”.

     charset
             Indicates to the server the character set of the strings for the searching methods.
             This variable takes a string as a value.  By default no character set is set, and
             thus plain ASCII should be assumed by the server.

     create  According to the IMAP specification, when trying to write a message to a non-
             existent mailbox, the server must send a hint to the client, whether it should
             create the mailbox and try again or not. However some IMAP servers don't follow the
             specification and don't send the correct response code to the client. By enabling
             this option the client tries to create the mailbox, despite of the server's
             response. This variable takes a boolean as a value.  Default is “false”.

     close   This option controls whether the currently selected mailbox is implicitly closed at
             the end of each performed operation, thus removing all messages that are marked
             deleted. This variable takes a boolean as a value.  Default is “false”.

     crammd5
             When this option is enabled and the server supports the Challenge-Response
             Authentication Mechanism (specifically CRAM-MD5), this method will be used for user
             authentication instead of a plaintext password LOGIN.  This variable takes a boolean
             as a value.  Default is “true”.

     expunge
             Normally, messages are marked for deletion and are actually deleted when the mailbox
             is closed.  When this option is enabled, messages are expunged immediately after
             being marked deleted.  This variable takes a boolean as a value.  Default is “true”.

     info    When this options is enabled, a summary of the program's actions is printed, while
             processing mailboxes.  This variable takes a boolean as a value.  Default is “true”.

     keepalive
             The time in minutes before terminating and re-issuing the IDLE command, in order to
             keep alive the connection, by resetting the inactivity timeout of the server.  A
             standards compliant server must have an inactivity timeout of at least 30 minutes.
             But it may happen that some IMAP servers don't respect that, or some intermediary
             network device has a shorter timeout.  By setting this option the above problem can
             be worked around. This variable takes a number as a value. Default is “29” minutes.

     limit   Some servers have problems handling very long requests, but some of the requests
             that need to be sent can become quite long, because they apply an action for many
             messages at once.  When this option is set, the client will try to break up these
             requests into smaller requests, that each operates on fewer messages at a time.  A
             good value for this would be “50”.  This variable takes a number as a value.
             Default is “0”.  See also the range option which is related.

     namespace
             When enabled, the program gets the namespace of the user's personal mailboxes, and
             applies automatically the prefix and hierarchy delimiter to any mailboxes residing
             on the mail server; the user must use the ‘/’ character as the delimiter and “” (ie.
             nothing) as the prefix, regardless of the folder format of the mail server.  This
             must be disabled, if the user wants to manually specify mailbox names (eg. because
             they are not part of the user's personal namespace mailboxes).  This variable takes
             a boolean as a value.  Default is “true”.

     persist
             When the recover option is enabled, the recovery function tries to restore the lost
             session, but if it fails to do so it gives up with an error.  In some cases a
             temporary network problem might cause the recovery function to fail, but the
             connection could be reestablished when trying a bit later.  By enabling this option,
             the recovery function will be called repeatedly after a timeout, thus it will
             persist when trying to restore the session.  Note, that this will case the execution
             of the configuration file to be halted at the point of failure until the session is
             restored, which can have side effects to other established sessions, for example
             they might get dropped by the server after a while.  This variable takes a boolean
             as a value.  Default is “false”.

     range   Some servers have problems handling long sequence number ranges, and by setting this
             option, the number of messages included in each range can be limited.  A good value
             for this would be “50”.  This variable takes a number as a value.  By default no
             such limit is imposed.  See also the limit option which is related.

     recover
             With this option it is possible to control the recovery functionality, which
             restores a session (the connection to the server and the IMAP state at the time),
             after some unexpected event takes place.  Currently there are two types of events
             that can end abnormally a session, and finally cause the program to terminate:
             network errors, and the IMAP BYE response which a server can send anytime.  When
             this option is set to “all” the recovery function is triggered by both types of
             events, when set to “errors” only in the case of network errors, and when set to
             “none” the mechanism is completely disabled.  Default is “all”.

     reenter
             When this option is enabled and the connection is recovered after some unexpected
             event while in IDLE mode (see also the recover option), the client will re-enter
             IDLE mode.  But when this option is disabled, and after the connection is recovered,
             the client will not re-enter IDLE mode, and instead will continue to execute the
             next line in the configuration file, ie. the one after enter_idle().  Default is
             “true”.

     starttls
             When this option is enabled and the server supports the IMAP STARTTLS extension, a
             TLS connection will be negotiated with the mail server in the beginning of the
             session.  This variable takes a boolean as value.  Default is “true”.

     subscribe
             By enabling this option new mailboxes that were automatically created, get also
             subscribed; they are set active in order for IMAP clients to recognize them.  This
             variable takes a boolean as a value.  Default is “false”.

     timeout
             The time in seconds for the program to wait for a mail server's response.  If set to
             0, the client will block indefinitely.  This variable takes a number as a value.
             Default is “60” seconds.

     wakeonany
             By enabling this option the IDLE command will return on any event that is received
             from the server, and not just on the “RECENT” and “EXISTS” events, that normally
             indicate the arrival of a new message.  Examples of other events are “FETCH”, which
             indicates that the details of a message (eg. its flags) have been modified, or
             “EXPUNGE”, which indicates that a message has been deleted.  This variable takes a
             boolean as a value.  Default is “false”.

ACCOUNTS

     Accounts are initialized using the IMAP() function, and the details of the connection are
     defined using an account table:

         myaccount = IMAP {
             server = 'imap.mail.server',
             username = 'me',
             password = 'secret',
             ssl = 'auto'
         }

     An account table must have the following elements:

     server  The hostname of the IMAP server to connect to.  It takes a string as a value.

     username
             User's name.  It takes a string as a value.

     An account table can also have the following optional elements:

     password
             User's secret keyword.  If a password wasn't supplied the user will be asked to
             enter one interactively the first time it will be needed (unless oauth2 has been
             set).  It takes a string as a value.

             Note that due to Lua using backslash ‘\’ as an escape character for its strings, one
             has to use double backslashes in order to insert a single backslash, and thus a
             backslash character inside a password might require four backslashes.

     oauth2  The OAuth2 string to use to authenticate if the server supports the XOAUTH2
             authentication mechanism.  If the server does not support it and a password has been
             also set, authentication will be attempted using the password.  It takes a string as
             a value.

             Note that this requires that an OAuth client ID and client secret have been
             obtained, an OAuth2 token has been generated and authorized, a new access token has
             been generated using the refresh token if the last access token has expired, and an
             OAuth2 string has been generated from the access token.  The aforementioned OAuth2
             string is a Base64 encoded string that should be set here.  For more information see
             https://developers.google.com/gmail/xoauth2_protocol.

     port    The port to connect to.  It takes a number as a value.  Default is “143” for imap
             and “993” for imaps.

     ssl     Forces an imaps connection and specifies the SSL/TLS protocol/version to be used.
             It takes a string as a value, specifically one of: “auto”, “tls1.2”, “tls1.1”,
             “tls1”, “ssl3”.

             Note that the latest versions of the OpenSSL library have deprecated version
             specific methods, and the actual protocol version used will be negotiated to be the
             highest version mutually supported by the client and the server.  This is also what
             the “auto” value does.

   LISTING
     The following methods can be used on an account to list mailboxes in a folder of an account:

     list_all(folder)
             Lists all the available mailboxes in the folder (string), and returns a table that
             contains strings, the available mailboxes, and a table that contains strings, the
             available folders.

     list_subscribed(folder)
             Lists all the subscribed mailboxes in the folder (string), and returns a table that
             contains strings, the subscribed mailboxes, and a table that contains strings, the
             subscribed folders.

     The following methods can be used on an account to list mailboxes, using wildcards, in a
     folder of an account.  The ‘*’ wildcard, matches any character and the ‘%’ matches any
     character except the folder delimiter, ie.  non-recursively:

     list_all(folder, mailbox)
             Lists all the available mailboxes in the folder (string) with the name mailbox
             (string), and returns a table that contains strings, the available mailboxes, and a
             table that contains strings, the available folders.  Wildcards may only be used in
             the mailbox argument.

     list_subscribed(folder, mailbox)
             Lists all the subscribed mailboxes in the folder (string) with the name mailbox
             (string), and returns a table that contains strings, the subscribed mailboxes, and a
             table that contains strings, the subscribed folders.  Wildcards may only be used in
             the mailbox argument.

     Examples:

         mailboxes, folders = myaccount:list_subscribed('myfolder')
         mailboxes, folders = myaccount:list_all('myfolder/mysubfolder', '*')

   MANIPULATING
     The following methods can be used to manipulate mailboxes in an account:

     create_mailbox(name)
             Creates the name (string) mailbox.

     delete_mailbox(name)
             Deletes the name (string) mailbox.

     rename_mailbox(oldname, newname)
             Renames the oldname (string) mailbox to newname (string).

     subscribe_mailbox(name)
             Subscribes the name (string) mailbox.

     unsubscribe_mailbox(name)
             Unsubscribes the name (string) mailbox.

     Examples:

         myaccount:create_mailbox('mymailbox')
         myaccount:subscribe_mailbox('mymailbox')
         myaccount:unsubscribe_mailbox('myfolder/mymailbox')
         myaccount:delete_mailbox('myfolder/mymailbox')

MAILBOXES

     After an IMAP account has been initialized, mailboxes residing in that account can be
     accessed simply as elements of the account table:

         myaccount.mymailbox

     If mailbox names don't only include letters, digits and underscores, or begin with a digit,
     an alternative form must be used:

         myaccount['mymailbox']

     A mailbox inside a folder can be only accessed by using the alternative form:

         myaccount['myfolder/mymailbox']

     The methods that are available for an account (eg.  list_all(), create_mailbox(), etc.) ,
     are considered keywords and must not be used as mailbox names, and the same also applies for
     any string starting with an underscore, as they are considered reserved.

   CHECKING
     The following methods can be used to check the status of a mailbox:

     check_status()

             The check_status() method gets the current status of a mailbox, and returns four
             values of number type: the total number of messages, the number of recent messages,
             the number of unseen messages in the mailbox, and the next UID to be assigned to a
             new message in the mailbox.

     enter_idle()
             The enter_idle() method implements the IMAP IDLE (RFC 2177) extension.  By using
             this extension it's not necessary to poll the server for changes to the selected
             mailbox (ie.  using the check_status() method), but instead the server sends an
             update when there is a change in the mailbox (eg. in case of new mail).  When the
             enter_idle() method has been called no more commands in the configuration file are
             executed until an update is received, at which point the enter_idle() method
             returns.  For the enter_idle() to work, the IDLE extension has to be supported by
             the IMAP server.

             The enter_idle() method returns a value of type boolean: “true” if the IDLE
             extension is supported and there was a update in the mailbox, and “false” if the
             IDLE extension is not supported, in which case the method returns immediately.  When
             the aforementioned return value was “true”, an additional second value of type
             string is also returned, indicating the event received from the server, which is
             useful when the wakeonany option has been enabled.

             Apart from an event received by the server, the SIGUSR1 or SIGUSR2 signals can also
             interrupt the IDLE mode at any time, and the execution of the configuration file
             will then continue from the next line after the enter_idle().  In this case only the
             value “true” is returned.

     Examples:

         exist, unread, unseen, uidnext = myaccount.mymailbox:check_status()
         update = myaccount.mymailbox:enter_idle()
         update, event = myaccount.mymailbox:enter_idle()

   SEARCHING
     The searching methods in this subsection can be applied to any mailbox.  They return a
     special form of table, that contains the messages that match the searching method.  This
     table can be combined with other tables using logic theory. There are three available
     operations, that implement logical “or”, logical “and” and logical “not”.

     The logical “or” is implemented using the ‘+’ operator:

         results = myaccount.mymailbox:is_unseen() +
                   myaccount.mymailbox:is_larger(100000)

     The logical “and” is implemented using the ‘*’ operator:

         results = myaccount.mymailbox:is_unseen() *
                   myaccount.mymailbox:is_larger(100000)

     The logical “not” is implemented using the ‘-’ operator:

         results = myaccount.mymailbox:is_unseen() -
                   myaccount.mymailbox:is_larger(100000)

     The three logical operators can be combined in the same expression. The logical “and” has
     higher precedence than the logical “or” and the logical “not”, with the latter two having
     the same precedence, and parentheses may be used to change this behaviour:

         results = myaccount.mymailbox:is_unseen() +
                   myaccount.mymailbox:is_larger(100000) *
                   myaccount.mymailbox:contain_subject('test')

         results = ( myaccount.mymailbox:is_unseen() +
                     myaccount.mymailbox:is_larger(100000) ) *
                     myaccount.mymailbox:contain_subject('test')

     The returned tables of the searching methods can also be stored in variables and then
     further processed:

         unseen = myaccount.myaccount:is_unseen()
         larger = myaccount.mymailbox:is_larger(100000)
         subject = myaccount.mymailbox:contain_subject('test')
         results = unseen + larger * subject

     A composite filter that includes one or more simple rules can be defined:

         myfilter = function ()
                        return myaccount.mymailbox:is_unseen() +
                               myaccount.mymailbox:is_larger(100000) *
                               myaccount.mymailbox:contain_subject('test')
                    end

         results = myfilter()

     Composite filters can may be more dynamic by adding arguments:

         myfilter = function (mailbox, size, subject)
                        return mailbox:is_unseen() +
                               mailbox:is_larger(size) *
                               mailbox:contain_subject(subject)
                    end

         results = myfilter(myaccount.mailbox, 100000, 'test')

     It is also possible to combine the searching methods in different mailboxes, either at the
     same or different accounts, for example when the same actions will be executed on messages
     residing in different mailboxes or accounts.

         results = myaccount.mymailbox:is_unseen() +
                   myaccount.myothermailbox:is_larger(100000) +
                   myotheraccount.myothermailbox:contain_subject('test')

     And for those that want to know more about the return values of the following methods, it is
     a table which contains tables with two values: the mailbox (table) the message belongs to,
     and the message UID (number) which points to the matching message.  For examples on
     iterating these returned tables, or creating new tables of this format (they are actually
     metatables implementing sets), see the samples/extend.lua file.

         {
             { <myaccount.mymailbox>, 1 },
             { <myaccount.mymailbox>, 3 },
             { <myaccount.myothermailbox>, 5 },
             { <myothermailbox.myothermailbox>, 7},
             { ... },
             ...
         }

     The following method can be used to get all messages in a mailbox:

     select_all()
             All messages.

     The following methods can be used to search for messages that are in a specific state:

     is_answered()
             Messages that have been answered.

     is_deleted()
             Messages that are marked for later removal.

     is_draft()
             Messages that have not completed composition.

     is_flagged()
             Messages that are flagged for urgent/special attention.

     is_new()
             Messages that are recently arrived (this session is the first to have been notified
             about these messages) and have not been read.

     is_old()
             Messages that are not recently arrived (this session is not the first to have been
             notified about these messages) and have not been read.

     is_recent()
             Messages that are recently arrived (this session is the first to have been notified
             about these messages).

     is_seen()
             Messages that have been read.

     is_unanswered()
             Messages that have not been answered.

     is_undeleted()
             Messages that are not marked for later removal.

     is_undraft()
             Messages that have completed composition.

     is_unflagged()
             Messages that are not flagged for urgent/special attention.

     is_unseen()
             Messages that have not been read.

     The following method can be used to search for messages that have a specific keyword flag
     set:

     has_keyword(flag)
             Messages with the specified keyword flag (string) set.
     has_unkeyword(flag)
             Messages without the specified keyword flag (string) set.

     The following methods can be used to search for messages based on their size:

     is_larger(size)
             Messages that are larger than the size (number) in octets (bytes).

     is_smaller(size)
             Messages that are smaller than the size (number) in octets (bytes).

     The following methods can be used to search for messages based on their age:

     is_newer(age)
             Messages that are newer than the age (number) in days.

     is_older(age)
             Messages that are older than the age (number) in days.

     The following methods can be used to search for messages based on their arrival or sent
     date, in the “day-month-year” form, where day is the day of the month as a decimal number
     (01-31), month is the abbreviated month ( “Jan”, “Feb”, “Mar”, “Apr”, “May”, “Jun”, “Jul”,
     “Aug”, “Sep”, “Oct”, “Nov”, “Dec”) and year is the year as decimal number including the
     century (eg. 2007):

     arrived_before(date)
             messages that have arrived earlier than the date (string), where date is in the
             “day-month-year” form.

     arrived_on(date)
             Messages that have arrived within the date (string), where date is in the
             “day-month-year” form.

     arrived_since(date)
             Messages that have arrived within or later than the date (string), where date is in
             the “day-month-year” form.

     sent_before(date)
             Messages that have been sent earlier than the date (string), where date is in the
             “day-month-year” form.

     sent_on(date)
             Messages that have been sent within the date (string), where date is in the
             “day-month-year” form.

     sent_since(date)
             Messages that have been sent within or later than the date (string), where date is
             in the “day-month-year” form.

     The following methods can be used to do case-insensitive searching, for messages that
     contain a specific word or phrase:

     contain_bcc(string)
             Messages that contain the string (string) in the “Bcc” header field.

     contain_cc(string)
             Messages that contain the string (string) in the “Cc” header field.

     contain_from(string)
             Messages that contain the string (string) in the “From” header field.

     contain_subject(string)
             Messages that contain the string (string) in the “Subject” header field.

     contain_to(string)
             Messages that contain the string (string) in the “To” header field.

     contain_field(field, string)
             Messages that contain the string (string) in the field (string) header field.

     contain_body(string)
             Messages that contain the string (string) in the message body.

     contain_message(string)
             Messages that contain the string (string) in the message.

     The following methods can be used to do case-sensitive searching, for messages that match a
     specific regular expression pattern. The matching mechanism that is used to support this is
     based on the Perl-compatible regular expressions (PCRE), and more information about the
     patterns and modifiers that can be used, is available in the relevant documentation at
     http://pcre.org/original/doc/html/.

     This way of searching is not supported by the IMAP protocol, and this means that what
     actually happens under the hood, is that the relevant parts of all the messages are
     downloaded and matched locally.  It is therefore recommended to use these methods with meta-
     searching (see following section), in order to narrow down the set of messages that should
     be searched, and thus minimize what will be downloaded.

     Note that due to Lua using backslash ‘\’ as an escape character for its strings, one has to
     use double backslashes in order to insert a single backslash inside a regular expression
     pattern:

     match_bcc(pattern)
             Messages that match the regular expression pattern (string) in the “Bcc” header
             field.

     match_cc(pattern)
             Messages that match the regular expression pattern (string) in the “Cc” header
             field.

     match_from(pattern)
             Messages that match the regular expression pattern (string) in the “From” header
             field.

     match_subject(pattern)
             Messages that match the regular expression pattern (string) in the “Subject” header
             field.

     match_to(pattern)
             Messages that match the regular expression pattern (string) in the “To” header
             field.

     match_field(field, pattern)
             Messages that match the regular expression pattern (string) in the field (string)
             header field.

     match_header(pattern)
             Messages that match the regular expression pattern (string) in the message header.

     match_body(pattern)
             Messages that match the regular expression pattern (string) in the message body.

     match_message(pattern)
             Messages that match the regular expression pattern (string) in the message.

     The following method can be used to search for messages using user queries based on the IMAP
     specification (RFC 3501 Section 6.4.4):

     send_query(criteria)
             Searches messages by sending an IMAP search query as described in the search
             criteria (string).

     Examples:

         results = myaccount.mymailbox:select_all()
         results = myaccount.mymailbox:is_new()
         results = myaccount.mymailbox:is_recent()
         results = myaccount.mymailbox:is_larger(100000)
         results = myaccount.mymailbox:is_older(10)
         results = myaccount.mymailbox:has_keyword('MyFlag')
         results = myaccount.mymailbox:arrived_before('01-Jan-2007')
         results = myaccount.mymailbox:sent_since('01-Jan-2007')
         results = myaccount.mymailbox:contain_subject('test')
         results = myaccount.mymailbox:contain_field('Sender', 'user@host')
         results = myaccount.mymailbox:contain_body('hello world')
         results = myaccount.mymailbox:match_from('.*(user1|user2)@host')
         results = myaccount.mymailbox:send_query('ALL')

         results = myaccount['mymailbox']:is_new()
         results = myaccount['myfolder/mymailbox']:is_recent()

RESULTS

     After one of more searching methods have been applied to one or more mailboxes, the result
     contains all the necessary information, such as which messages matched in which mailboxes.
     Using this result these messages can be either searched further or processed in various way.

   META-SEARCHING
     The results of the searching methods can be searched further on in the same way as searching
     is done in mailboxes.  The difference is that instead of doing the search in the whole
     mailbox, ie. in all the messages, it is instead done only to those messages that were
     returned in a previous search.

     Examples:

         results:match_message('^[Hh]ello world!?$')
         myaccount.mymailbox:is_new():match_body('^[Ww]orld, hello!?$')

   PROCESSING
     The processing methods are applied to the results that searching returned.

     The following method can be used to delete messages in a mailbox:

     delete_messages()
             Deletes the messages that matched.

     The following methods can be used to copy and move messages in a mailbox at the same or
     different accounts.  If the destination mailbox is in a different account than the source
     mailbox, then the messages are downloaded and then uploaded to the destination:

     copy_messages(destination)
             Copies the messages to the destination, which is a mailbox at an account.

     move_messages(destination)
             Moves the messages to the destination, which is a mailbox at an account.

     The following methods can be used to mark messages in a mailbox:

     mark_answered()
             Marks the messages as answered.

     mark_deleted()
             Marks the messages for later removal.

     mark_draft()
             Marks the messages as draft.

     mark_flagged()
             Marks the messages for urgent/special attention.

     mark_seen()
             Marks the messages as read.

     unmark_answered()
             Unmarks the messages that have been marked as answered.

     unmark_deleted()
             Unmarks the messages that have been marked for later removal.

     unmark_draft()
             Unmarks the messages that have been marked as draft.

     unmark_flagged()
             Unmarks the messages that have been marked for urgent/special attention.

     unmark_seen()
             Unmarks the messages that have been marked as read.

     The following methods can be used to flag messages in a mailbox. The standard system flags
     are “\Answered”, “\Deleted”, “\Draft”, “\Flagged”, “\Seen”, while if the server supports it,
     new user keywords may be defined:

     add_flags(flags)
             Adds the flags (table that contains strings) to the messages.

     remove_flags(flags)
             Removes the flags (table that contains strings) from the messages.

     replace_flags(flags)
             Replaces the flags (table that contains strings) of the messages.

     Examples:

         results:delete_messages()
         results:copy_messages(myaccount.myothermailbox)
         results:move_messages(myotheraccount.mymailbox)
         results:mark_seen()
         results:unmark_flagged()
         results:add_flags({ 'MyFlag', '\\Seen' })
         results:remove_flags({ '\\Seen' })

         results:move_messages(myotheraccount['myfolder/mymailbox'])

MESSAGES

     The messages that are residing in any mailbox can be also accessed, as a whole or in parts.
     Messages can be accessed using their unique identifier (UID):

         myaccount.mymailbox[22]

     The UIDs of messages the user is interested in, are gained from the results of searching:

         results = account.INBOX:is_unseen()
         for _, message in ipairs(results) do
             mailbox, uid = table.unpack(message)
             header = mailbox[uid]:fetch_header()
         end

   FETCHING
     The following methods can be used to fetch parts of messages.  The methods return a string.
     The downloaded message parts are cached locally, so they can be reused inside the same
     program session:

     fetch_message()
             Fetches the header and body of the message.

     fetch_header()
             Fetches the header of the message.

     fetch_body()
             Fetches the body of the messages.

     fetch_field(field)
             Fetches the specified header field (string) of the message.

     fetch_part(part)
             Fetches the specified part (string) of the message.

     The following methods can be used to fetch details about the state of a message:

     fetch_flags()
             Fetches the flags of the message.  Returns a table of strings.

     fetch_date()
             Fetches the internal date of the message.  Returns a string.

     fetch_size()
             Fetches the size of the message.  Returns a number.

     fetch_structure()
             Fetches the body structure of the message. Returns a table that has as keys the
             parts of the message, and as values a table that has one mandatory element, the type
             (string) of the part, and two optional elements, the size (number) and name (string)
             of the part.

   APPENDING
     The following methods can be used to append a message to a mailbox:

     append_message(message)
             Appends the message (string) to the mailbox.

     append_message(message, flags, date)
             Appends the message (string) to the mailbox, setting the specified flags (table of
             strings), as returned by fetch_flags(), and date (string), as returned by
             fetch_date().

     Examples:

         myaccount.mymailbox[2]:fetch_message()
         myaccount.mymailbox[3]:fetch_field('subject')
         myaccount.mymailbox[5]:fetch_part('1.1')

         myaccount['mymailbox'][7]:fetch_message()
         myaccount['myfolder/mymailbox'][11]:fetch_message()

         myaccount.mymailbox:append_message(message)

FUNCTIONS

     The following auxiliary functions are also available for convenience:

     form_date(days)
             Forms a date in “day-month-year” format that the system had before the number of
             days (number), and returns it as a string.

     get_password(prompt)
             Displays the specified prompt (string), and reads a password, while character
             echoing is turned off.  Returns that password as a string.

     become_daemon(interval, commands)
             Detaches the program from the controlling terminal and runs it in the background as
             system daemon. The program will then repeatedly poll at the specified interval
             (number) in seconds. Each time the program wakes up, the commands (function) are
             executed.

     become_daemon(interval, commands, nochdir, noclose)
             Detaches the program from the controlling terminal and runs it in the background as
             system daemon. The program will then repeatedly poll at the specified interval
             (number) in seconds. Each time the program wakes up, the commands (function) are
             executed.

             If nochdir (boolean) is “true”, the current working directory is not changed to the
             root directory (/).  If noclose (boolean) is “true”, the standard input, standard
             output and standard error are not redirected to /dev/null.

     pipe_to(command, data)
             Executes the system's command (string) and sends the data (string) to the standard
             input channel of the subprocess. Returns a number, the exit status of the child
             process.

     pipe_from(command)
             Executes the system's command (string) and retrieves the data from the standard
             output channel of the subprocess.  Returns a number, the exit status of the child
             process, and a string, the output of the child process.

     regex_search(pattern, string)
             Implements Perl-compatible regular expressions (PCRE). The pattern (string) is a
             PCRE pattern. The string (string) is the subject string in which the pattern is
             matched against. Returns at least a boolean, that denotes if the match was
             successful, and any captures which are of string type.  Note that due to Lua using
             backslash ‘\’ as an escape character for its strings, one has to use double
             backslashes in order to insert a single backslash inside a regular expression
             pattern.  For more information on PCRE see http://pcre.org/original/doc/html/.

     Examples:

         date = form_date(14)
         password = get_password('Enter password: ')
         become_daemon(600, myfunction)
         status = pipe_to('mycommandline', 'mydata')
         status, data = pipe_from('mycommandline')
         success, capture = regex_search('^(?i)pcre: (\\w)$', 'mystring')

EXAMPLES

     See samples/config.lua and samples/extend.lua in the source code distribution.

ENVIRONMENT

     HOME    User's home directory.

SEE ALSO

     imapfilter(1)