IMAPFILTER_CONFIG(5)

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, 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”.

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”.

hostnames
    When this option is enabled, the server hostname is validated, in order to verify the client is talking to the correct server. This variable takes a boolean as a value. Default is “true”.

info
    When this option 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 some IMAP servers might not 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 “” (i.e. 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 (e.g. because they are not part of the user's personal namespace mailboxes). This variable takes a boolean as a value. Default is “true”.

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.

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 (e.g. 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.

    Passwords can also be extracted during execution time from an encrypted password vault. The samples/extend.lua file contains such an example.

    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 also been 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.

    The samples/extend.lua file contains an example of authentication using OAuth2.

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, i.e. 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 (e.g. 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 (i.e. using the check_status() method), but instead the server sends an update when there is a change in the mailbox (e.g. 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 an 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.mymailbox: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 (e.g. 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 also be 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 three optional elements, the size (number), name (string) and encoding (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)
become_daemon(interval, commands, nochdir)
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/.

sleep(interval)
    Delay for the specified interval (number) in seconds.

recover(commands)
recover(commands, retries)
    Protects the commands (function) executed from raising an error. Whenever an error is raised, it sleeps for a few seconds (using exponential backoff up to some upper limit), and then re-executes the commands (function) from start.

    If the maximum count of retries (number) is specified, it will retry up to the specified number of times, otherwise it will never give up.

    Returns the status code of the execution as the first result, “true” if it succeeded or “false” if it failed. If it succeeded, it returns all values the commands (function) returned as additional results. If it failed, it returns the error as an additional result.

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')
    sleep(300)
    recover(myfunction, 5)

For more examples, see the samples/extend.lua file.

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

ENVIRONMENT

HOME
    User's home directory.

SEE ALSO
imapfilter(1)