FDM.CONF(5) File Formats Manual FDM.CONF(5)

fdm.conffdm configuration file

This manual page describes the fdm(1) configuration file. It defines accounts from which to fetch mail, a number of possible actions to take, and connecting a regexp with an action. The file is parsed once from top to bottom, so action and account definitions must appear before they are referenced in a rule. Rules are evaluated from first to last and (unless overridden by the continue keyword) evaluation stops at the first match.

The file has the following format:

Empty lines and lines beginning with the ‘#’ character are ignored.

Regexps and strings must be enclosed in double quotes. Special characters in regexps and strings (including passwords) must be escaped. Note that this may mean double-escaping in regexps.

Possible commands are covered in the following sections.

Options are configured using the set command. It may be followed by the following options, one per command:

This is used to set the maximum size of a mail. Mails larger than this limit are dropped and, if applicable, not deleted from the server.

The size may be specified as a plain number in bytes or with a suffix of ‘K’ for kilobytes, ‘M’ for megabytes or ‘G’ for gigabytes. The default is 32 megabytes and the maximum is one gigabyte.

If this option is specified, fdm(1) attempts to delete messages which exceed maximum-size, and continue. If it is not specified, oversize messages are a fatal error and cause fdm(1) to abort.

Note that fdm(1) may have a number of messages queued (up to the queue-high setting, doubled for rewrite, per account), so this setting and the queue-high option should be set after consideration of the space available in the temporary folder and the implications should fdm(1) abort due to the space becoming full.

This sets the maximum number of messages fdm(1) will hold simultaneously. fdm(1) will attempt to process previously queued messages as the next is being fetched. Once this limit is reached, no further messages will be fetched until the number of messages held drops to the queue-low value.
This is the length to which the message queue must drop before fetching continues after the queue-high limit has been reached.
If set, fdm.conf will continue to process mail if a delivery fails rather than aborting.
If this option is specified, fdm(1) does not attempt to create a lock file and allows multiple instances to run simultaneously.
This sets an alternative lock file. The default is ~/.fdm.lock for non-root users and /var/db/fdm.lock for root.
Sets how long fdm.conf will try a lock file before giving up.
If present, fdm.conf will wait for lock-file for lock-timeout rather than exiting immediately with an error.
This specifies the user used to run exec and pipe actions. By default it is the user who invoked fdm.
This sets the default user to change to before delivering mail, if fdm(1) is running as root and no alternative user is specified as part of the action or rule. This option may be overridden with the -u switch on the command line. A default user must be given if running as root.
location ...
This specifies the order in which to do user lookup from left to right. Possible types are passwd to use the passwd(5) file, or courier to use Courier authlib (if support is compiled).
type ...
This specifies the locks to be used for mbox locking. Possible types are fcntl, flock, and dotlock. The flock and fcntl types are mutually exclusive. The default is flock.
This instructs fdm(1) to proxy all connections through url. HTTP and SOCKS5 proxies are supported at present (URLs of the form http://host[:port] or socks://[user:pass@]host[:port]). No authentication is supported for HTTP.
drop |
This option controls what fdm(1) does with mail that reaches the end of the ruleset (mail that matches no rules or matches only rules with the continue keyword). drop will cause such mail to be discarded, and keep will attempt to leave the mail on the server. The default is to keep the mail and log a warning that it reached the end of the ruleset.
The purge-after option makes fdm(1) attempt to purge deleted mail from the server (if supported) after count mails have been retrieved. This is useful on unreliable connections to limit the potential number of mails refetched if the connection drops, but note that it can incur a considerable speed penalty.
If this option is present, fdm(1) will not insert a ‘Received’ header into each mail.
If this option is set, fdm(1) will not attempt to create maildirs and mboxes or missing elements of their paths.
user | umask
This specifies the umask(2) to use when creating files. user means to use the umask set when fdm(1) is started, or umask may be specified as a three-digit octal number. The default is 077.
user | group
This option allows the default group ownership of files and directories created by fdm(1) to be specified. group may be a group name string or a numeric gid. If user is used, or this option does not appear in the configuration file, fdm(1) does not attempt to set the group of new files and directories.
This controls the maximum time to wait for a server to send data before closing a connection. The default is 900 seconds.
Instructs fdm(1) to verify SSL certificates for all SSL connections.

Further configuration files may be including using the include command:


The file to include is searched for first as an absolute path and then relative to the directory containing the main configuration file.

Macros may be defined using the following syntax:

  • name = string
  • name = number

Macros are prefixed with $ to indicate a string value and % to indicate a numeric value. Once defined, a macro may be used in any place a string or number is expected. Macros may be embedded in strings by surrounding their name (after the $ or %) with {}s, like so:

"abc ${mymacro} %{anothermacro} def"

The ifdef, ifndef and endif keywords may be used to conditionally parse a section of the configuration file depending on whether or not the macro given exists or does not exist. ifdef and ifndef blocks may be nested.

The result of a shell command may be used at any point a string or number is expected by wrapping it in $() or %(). If the former is used, the command result is used as a string; if the latter, it is converted to an integer. Shell commands are executed when the configuration file is parsed.

The account command is used to instruct fdm(1) to fetch mail from an account. The syntax is:

name [users] [disabled] type [args] [keep]

The name argument is a string specifying a name for the account. The optional users argument has the following form:

user | { user ... }

The first two options specify a user or list of users as which the mail should be delivered when an action is executed. If no users are specified, the default user (set with set default-user) is used. Users specified as part of the account definition may be overridden by similar arguments to action definitions or on match rules. If fdm(1) is run as non-root, it will still execute any actions once for each user, but will be unable to change to that user so the action will be executed multiple times as the current user.

The disabled keyword instructs fdm(1) to ignore this account unless it is explicitly enabled with a -a option on the command line. If the keep keyword is specified, all mail collected from this account is kept (not deleted) even if it matches a drop action.

Supported account types and arguments are:

This account type reads mail from stdin, if it is connected to a pipe. This may be used to deliver mail from sendmail(8), see fdm(1) for details.
server host [port port] [user user] [pass pass] [only] [no-apop] [no-uidl] [starttls] [insecure]
server host [port port] [userpass] [only] [no-apop] [no-verify] [no-uidl] [insecure]
These statements define a POP3 or POP3S account. The userpass element has the following form:
[user user] [pass pass]

The host, user and pass arguments must be strings. If the user or pass is not provided, fdm(1) attempts to look it up in the ~/.netrc file (see ftp(1) for details of the file format). The port option may be either a string which will be looked up in the services(5) database, or a number. If it is omitted, the default port (110 for POP3, 995 for POP3S) is used.

The only option takes the form:

[new-only | old-only] cache path

new-only fetches only mail not previously fetched, and old-only is the inverse: it fetches only mail that has been fetched before. The cache file is used to save the state of the POP3 mailbox. The no-apop flag forces fdm(1) not to use the POP3 APOP command for authentication, and the no-verify keyword instructs fdm(1) to skip SSL certificate validation for this account. The no-uidl keyword makes fdm(1) not use the UIDL command to retrieve mails. This is mainly useful for broken POP3 servers.

starttls attempts to use STARTTLS after connection.

insecure allows the use of insecure protocols, which currently includes SSLv2, SSLv3 and TLS1.0.

pipe command [userpass] [only] [no-apop]
This account type uses the POP3 protocol piped through command, such as ssh(1). If the command produces any output to stderr, it is logged. For POP3 over a pipe, providing a user and password is not optional and it may not be read from ~/.netrc.
server host [port port] [userpass] [folder name] [only] [no-cram-md5] [no-plain] [no-login] [starttls] [insecure] [oauthbearer] [xoauth2]
server host [port port] [userpass] [folders] { name ... } [only]
server host [port port] [userpass] [folders] [only] [no-verify] [no-cram-md5] [no-plain] [no-login] [insecure] [oauthbearer] [xoauth2]
These define an IMAP or IMAPS account. The parameters are as for a POP3 or POP3S account, aside from the additional folders option which sets the name of the folder or folders to use (the default is to fetch from the inbox). This has the form:
name | { name ... }

The default ports used are 143 for IMAP and 993 for IMAPS. For IMAP, the only item consists only of one of the keywords new-only or old-only - a cache file is not required.

Options no-cram-md5, no-plain and no-login disable the given authentication method. The default is to use CRAM-MD5 if it is available, then PLAIN, and LOGIN otherwise.

starttls attempts to use STARTTLS after connection.

insecure allows the use of insecure protocols, which currently includes SSLv2, SSLv3 and TLS1.0.

oauthbearer attempts to use OAuth 2.0 bearer token as authentication method.

pipe command [userpass] [folders] [only]
As with pop3 pipe, this account type uses the IMAP protocol piped through command. If the optional IMAP user and pass are supplied, they will be used if necessary, but if one is provided, both must be – using ~/.netrc is not permitted.

Mail fetched using the IMAP protocol is tagged with a folder tag containing the source folder name.

{ path ... }
These account types instruct fdm(1) to fetch mail from the maildir or maildirs specified. This allows fdm(1) to be used to filter mail, fetching from a maildir and deleting (dropping) unwanted mail, or delivering mail to another maildir or to an mbox.

Mail fetched from a maildir is tagged with a maildir tag containing the basename of the mail file.

{ path ... }
These are similar to maildir and maildirs, but cause fdm(1) to fetch mail from an mbox or set of mboxes.

Mail fetched from a mbox is tagged with a mbox tag containing the basename of the mbox file.

server host [port port] [userpass] group group cache cache
server host [port port] [userpass] groups { group ... } cache cache
server host [port port] [userpass] group group cache cache
server host [port port] [userpass] groups { group ... } cache cache
An NNTP account. Articles are fetched from the specified group or groups and delivered. The index and message-id of the last article fetched in each group is saved in the specified cache file. When fdm(1) is run again, fetching begins at the cached article. Note that the keep option is completely ignored for NNTP accounts – all mail is kept, and the cache is always updated.

As mail is processed by fdm(1), it is tagged with a number of name/value pairs. Some tags are added automatically, and mail may also be tagged explicitly by the user using the tag action. Tags may be inserted in most strings in a similar manner to macros, except tags are processed at runtime rather than as the configuration file is parsed. A tag's value is inserted by wrapping its name in %[], for example:


The default tags also have a single-letter shorthand. Including a nonexistent tag in a string is equivalent to including a tag with an empty value, so "abc%[nonexistent]def" will be translated to "abcdef".

The automatically added tags are:

account (%a)
The name of the account from which the mail was fetched.
home (%h)
The delivery user's home directory.
uid (%n)
The delivery user's uid.
action (%t)
The name of the last action executed for this mail.
user (%u)
The delivery user's username.
hour (%H)
The current hour (00–23).
minute (%M)
The current minute (00–59).
second (%S)
The current second (00–59).
day (%d)
The current day of the month (01–31).
month (%m)
The current month (01–12).
year (%y)
The current year.
The current year as two digits.
dayofweek (%W)
The current day of the week (0–6, Sunday is 0).
dayofyear (%Y)
The current day of the year (001–366).
quarter (%Q)
The current quarter (1–4).
The current date in RFC822 format.
The hour from the mail's date header, if it exists and is valid, otherwise the current time.
The minute from the mail's date header.
The second from the mail's date header.
The day from the mail's date header.
The month from the mail's date header.
The year from the mail's date header.
The same as two digits.
The day of the week from the mail's date header.
The day of the year from the mail's date header.
The quarter (1–4) from the mail's date header.
The mail's date in RFC822 format.
The total number of lines in the message.
The number of lines in the body.
The number of lines in the header.
The message id from the mail's header (if present).
The local hostname.

In addition, the shorthand %% is replaced with a literal %, and %0 to %9 are replaced with the result of any bracket expressions in the last regexp.

fdm(1) can maintain a cache file with a set of user-defined strings. In order to use caches, fdm(1) must have been compiled with them enabled. Caches are declared with the cache keyword:

path [expire age]

The path is the location of the cache file. If the expire keyword is specified, items in the cache are removed after they reach the age specified. age may be given unadorned in seconds, or followed by one of the modifiers: seconds, hours, minutes, days, months or years.

Caches must be declared before they are used. Items are added to caches using the add-to-cache action, removed using the remove-from-cache action, and searched for using the in-cache condition; see below for information on these.

The action command is used to define actions. These may be specified by name in rules (see below) to perform some action on a mail. The syntax is:

name [users] action
name [users] { action ... }

The name is a string defining a name for the action. The users argument has the same form as for an account definition. An action's user setting may be overridden in the matching rule.

The possible values for action are listed below. If multiple actions are specified they are executed once in the order specified, for each user.

Discard the mail.
Keep the mail, do not remove it from the account.
string [value value]
This tags mail with string, and optionally value, which may be matched using the tagged or string conditions.
Save the mail to the maildir specified by path. If the maildir or any part of its path does not exist, it is created, unless the no-create option is set.

Mail delivered to a maildir is tagged with a mail_file tag containing the full path of the mail file.

path [compress]
Append the mail to the mbox at path. If compress is specified, fdm(1) will add ‘.gz’ to path and attempt to write mail using gzip(1) compression. If the mbox or any part of its path does not exist, it is created, unless the no-create option is set.

Mail delivered to an mbox is tagged with a mbox_file tag containing the path of the mbox.

Execute command.
Pipe the mail to command. exec and pipe commands are run as the command user.
Write the mail to path.
Append the mail to path.
server host [port port] [from from] [to to]
Connect to an SMTP server and attempt to deliver the mail to it. If from or to is specified, they are passed to the server in the MAIL FROM or RCPT TO commands. If not, the current user and host names are used.
server path | host [port port] [from from] [to to]
Connect to an LMTP server and attempt to store the mail there. If a UNIX socket is to be used, path must be the absolute pathname.

port defaults to 24. If from or to is specified, they are passed to the server in the MAIL FROM or RCPT TO commands. If not, the current user and host names are used.

Pipe the entire mail through command to generate a new mail and use that mail for any following actions or rules. An example of the rewrite action is:
action "cat" pipe "cat"
action "rewrite" rewrite "sed 's/bob/fred/g'"
# this rule will rewrite the message
match all action "rewrite" continue
# this rule will cat the rewritten message
match all action "cat"
name value value
Add a header name with contents value.
{ name ... }
Remove all occurrences of headers matching the fnmatch(3) pattern name.
Write the mail to stdout.
path key key
This action adds the string key to the cache specified by path. If key already exists in the cache, it is replaced.
path key key
Remove the string key from the cache path, if a matching key is present.
This invokes another named action. A maximum of five actions may be called in a sequence.

Rules are specified using the match keyword. It has the following basic form:

condition [and | or condition ...] [users] actions [continue]

The condition argument may be one of:

Matches all mail.
Matches only mail that has matched a previous rule and been passed on with continue.
The opposite of matched: matches only mails which have matched no previous rules.
name | { name ... }
Matches only mail fetched from the named account or accounts. The account names may include shell glob wildcards to match multiple accounts, as with the -a and -x command line options.
Matches mails tagged with string.
[case] regexp [in headers | in body]
Specifies a regexp against which each mail should be matched. The regexp matches may be restricted to either the headers or body of the message by specifying either in headers or in body. The case keyword forces the regexp to be matched case-sensitively: the default is case-insensitive matching.
command [user user] returns (return code, stdout regexp)
command [user user] returns (return code, [case] stdout regexp)
These two conditions execute a command and test its return value and output. The return code argument is the numeric return code expected and stdout regexp is a regexp to be tested against the output of the command to stdout. Either of these two arguments may be omitted: if both are specified, both must match for the condition to be true. The pipe version will pipe the mail to the command's stdin when executing it. If a user is specified, fdm(1) will change to that user before executing the command, otherwise the current user (or root if started as root) is used.
< number
> number
Compare the mail size with number.
string to [case] regexp
Match string against regexp.
< time
> time
The age condition examines the mail's date header to determine its age, and matches if the mail is older (>) or newer (<) than the time specified. The time may be given as a simple number in seconds, or followed by the word seconds, hours, minutes, days, months or years to specify a time in different units.
path key key
This condition evaluates to true if the string key is in the cache at path.
count < number
count > number
count == number
count != number
These conditions match if the mail possesses a number of attachments less than, greater than, equal to or not equal to number.
total-size < size
total-size > size
Matches if the total size of all attachments is smaller or larger than size.
any-size < size
any-size > size
Compare each individual attachment on a mail to size and match if any of them are smaller or larger.
any-type string
any-name string
Match true if any of a mail's attachments possesses a MIME type or filename that matches string. fnmatch(3) wildcards may be used.

Multiple conditions may be chained together using the and or or keywords. The conditions are tested from left to right. Any condition may be prefixed by the not keyword to invert it.

The optional users argument to the first form has the same syntax as for an action definition. A rule's user list overrides any users given as part of the actions.

The actions list specifies the actions to perform when the rule matches a mail. It is either of a similar form:

name | { name ... }

Or may specify a number of actions inline (lambda actions):

{ action ... }

In the latter case, action follows the same form as described in the ACTIONS section. The actions are performed from first to last in the order they are specified in the rule definition.

If the continue keyword is present, evaluation will not stop if this rule is matched. Instead, fdm(1) will continue to match further rules after performing any actions for this rule.

Rules may be nested by specifying further rules in braces:

condition [and | or condition ...] {

The inner rules will not be evaluated unless the outer one matches. Rules may be multiply nested. Note that the outer rule does not count as a match for the purposes of the matched and unmatched conditions.

default fdm.conf configuration file
default system-wide configuration file
default lock file
lock file for root user

fdm(1), re_format(7)

Nicholas Marriott <nicholas.marriott@gmail.com>

August 21, 2006 Linux 6.8.7-arch1-1