name class args
name is the symbolic name. The
class is the kind
of database to use (see Section 33.3.2, "The class").
args specifies the location and properties of the database file
(see Section 33.3.3, "The args").
We describe each in turn.
name portion of the
K configuration command immediately
K. Whitespace between the
K and the
name is optional.
name class argsoptional whitespace
The name must begin with a letter or digit and may contain only letters, digits, and the underscore character. For example:
K local_hosts good K $andCents bad
If you begin a
name with a bad character, the following error
will be printed and that
K line will be ignored:
num: readcf: config K line: no map name
If a bad character appears in the middle of a name, the part preceding the
bad character will be taken as the
name, and the part
following the bad character will be taken as the
me@home will produce this error:
num: readcf: map me: class home not available
The case of the letters in
name does not matter.
All names are converted to lowercase before they are stored.
Recall that the
class portion of the
command follows the
name class args
Note that whitespace between the
name and the
may be a joined indented line, which allows commenting and improves
name# Why this name
class# Why this class
args# and so on
class is the database type. It must be
one of the classes listed in
|btree||Section 33.8.1||V8.1 and above|
Berkeley's db form of database
|bestmx||Section 33.8.2, bestmx||V8.7 and above|
Look up the best MX record for a host
|dbm||Section 33.8.3||V8.1 and above|
Really ndbm supplied with most versions of UNIX
|dequote||Section 33.8.4, dequote||V8.1 and above|
A pseudo map for removing quotation marks
|hash||Section 33.8.5, hash||V8.1 and above|
Berkeley's db form of database
|hesiod||Section 33.8.6||V8.7 and above|
MIT network user authentication services
|host||Section 33.4.3, "$[ and $]: A Special Case"||V8.1 and above|
Internal table to store and look up hostnames
|implicit||Section 33.8.8, implicit||V8.1 and above|
Search for an aliases database file
|ldapx||Section 33.8.9||V8.8 and above|
The Lightweight Directory Access Protocol
|netinfo||Section 33.8.10||V8.7 and above|
NeXT Computers network information services
|nis||Section 33.8.11||V8.1 and above|
Sun's Network Information Services (NIS)
|nisplus||Section 33.8.12||V8.7 and above|
Sun's newer Network Information Services (NIS+)
|null||Section 33.8.13, null||V8.7 and above|
Provide a never found service
|program||Section 33.8.14, program||V8.7 and above|
Run an external program to look up the key
|sequence||Section 33.8.15, sequence||V8.7 and above|
Search a series of maps
|stab||Section 33.8.16, stab||V8.1 and above|
Internally load aliases into the symbol table
|switch||Section 33.8.17, switch||V8.7 and above|
Internal hook to auto-build sequences
|text||Section 33.8.18, text||V8.7 and above|
Look up in flat text files
|userdb||Section 33.8.19, userdb||V8.7 and above|
Look up in the User Database
|user||Section 33.8.20, user||V8.7 and above|
Look up local passwd information
All of these classes are described in Section 33.8, "Alphabetized Reference" at the end
of this chapter. If the
class is not one of those listed,
or if support for the
class was not compiled in, the following error
is printed and the
K command is ignored:
num: readcf: map mehome: class badclass not available
The case of the
class is ignored by sendmail. That is,
HASH are all the same.
args of the
K configuration command follow symbolic name and class type:
name class args
(among other things) the location of the database file or the name
of a network map. The
is like a miniature command line, and its general form looks
switches are letters prefixed with a
character that modify the use of the database. (We'll discuss
them in the next section.) The
is the location of the database file or the name of a network
file_or_map should exclude the .pag and .dir
suffixes for dbm class files and exclude
the .db suffix for hash or btree class files.
A database or map is opened for reading when the configuration
file is processed. If the
file cannot be opened (and
-o is omitted; see Section 188.8.131.52, "-o the database file is optional (V8.1 and above)"), an appropriate error
is printed. The
file_or_map should be an absolute pathname
of a file (such as /etc/uuhosts)
or a literal network map name (such as hosts.byname).
nis map specification can include a domain:
Relative filenames (names that omit a leading
/) are interpreted
as relative to the current directory of the process that invoked
sendmail and should never be used.
switches must follow the
class and precede
name class switches file_or_map
they are silently ignored.
switches begin with a
- character and
are listed in
 This is true as of version 8.8.4. Future versions may change the semantics of the
Kline such that switches may follow.
|Section 184.108.40.206, "-A append values for duplicate keys (V8.7 and above)"||V8.7 and above||Append values for duplicate keys|
|Section 220.127.116.11, "-a append tag on successful match (V8.1 and above)"||V8.1 and above||Append tag on successful match|
|Section 18.104.22.168, "-f don't fold keys to lowercase (V8.1 and above)"||V8.1 and above||Don't fold keys to lowercase|
|Section 22.214.171.124, "-k specify column for key (V8.7 and above)"||V8.7 and above||Specify column for key|
|Section 126.96.36.199, "-m suppress replacement on match (V8.1 and above)"||V8.1 and above||Suppress replacement on match|
|Section 188.8.131.52||V8.1 and above||Append a null byte to all keys|
|Section 184.108.40.206, "-O adaptive versus never add a null (V8.2 and above)"||V8.2 and above||Adaptive versus never add a null|
|Section 220.127.116.11||V8.1 and above||The database file is optional|
|Section 18.104.22.168, "-q don't strip quotes from key (V8.7 and above)"||V8.7 and above||Don't strip quotes from key|
|Section 22.214.171.124, "-s space replacement character (V8.7 and above)"||V8.7 and above||Space replacement character|
|Section 126.96.36.199, "-v specify the value's column (V8.7 and above)"||V8.7 and above||Specify the value's column|
|Section 188.8.131.52, "-z specify the column delimiter (V8.7 and above)"||V8.7 and above||Specify the column delimiter|
If a switch other than those listed is specified, that switch is silently ignored.
Not all switches work with all classes. Some classes use many switches; others use none. The switches that are used by each class are shown in Table 33.5.
Some classes of databases use special switches that are not available to the broad class of databases. Others redefine the meaning of some switches. These special switches are shown in Table 33.6. Future versions of sendmail may be changed in such a way that it may be possible to have only one list.
|Switch||Class or Vendor||Description|
Base from which to begin the search
Use domain wide information (see Section 38.16, "K Command's -d switch")
Host that serves this network database
Time limit to timeout connection
Retrieve attribute names only, not values
Port to use when connecting to host
Don't auto chase referrals
Search scope of "base," "one," or "sub"
staff: bill staff: leopold this is an error
But sometimes, in automating for example, such duplicates are necessary.
In such instances, the
-A switch can be used with the
A) option (see Section 34.8.1, AliasFile (A))
to cause duplicates to be silently appended:
staff: bill staff: leopold ... silently modified by sendmail to internally become staff: bill, leopold
Note that this process is further illustrated in Section 24.4.4, "Duplicate Entries and Automation".
-A database switch is useful only with alias files, because
those are the only files that sendmail rebuilds on its own.
When a key is looked up in a database (from inside the
$) operators of the RHS of rules), a successfully found
key is replaced by its data. If the
-a switch is
given, the text following that switch, up to the first delimiting
whitespace character, is appended to the replacement data. For example:
-a appends nothing -a. appends . -a,MAGICTOKEN appends ,MAGICTOKEN
The text to be appended is taken literally. Quotation marks and
backslashed characters are included without interpretation, so
whitespace cannot be included in that text. Because the rewritten
RHS is normalized as an address, special address expressions
(such as parentheses) should be avoided.
The use of appended text is one of two methods used for recognizing
a successful lookup in rules.
We'll discuss the other,
$:, in Section 33.4.1, "Specify a Default with $:".
Ordinarily, sendmail will normalize a key to lowercase
before looking it up in the database. If the keys in the database
are case-sensitive ("TEX" is considered different from "tex," for example),
-f switch should be used to prevent this normalization.
Note that if the
-f switch is omitted (the default), the database
must have been created with all lowercase keys (also the default).
When such files are read as databases (with the
see Section 33.8.18), you need to specify which column is the
key and which is the value.
netinfo maps, the
-k switch specifies the
name (text) of the desired column.
-k switch specifies which column is the key, its absence
defaults to 0 for the
text class and to
the name of the zeroth column for the
Note that the numbered columns are indexed beginning with 0 for the first
and 1 for the second. See also
-v (see Section 184.108.40.206)
for the value's column (
-z (see Section 220.127.116.11) for the column delimiter
Ordinarily, a successful lookup in a database or map causes the
key to be replaced by its value. When the intention is to merely verify
that the key exists (not replace it), the
can be used to suppress replacement.
For example, the values that are returned from the hosts.byname
NIS map are not generally useful (they contain multiple hostnames).
In looking up a key in this map (with
see Section 33.4), the
-m switch prevents
those multiple names from wrongly replacing the single hostname
in the key. Note that the
-a (see Section 18.104.22.168)
can still be used to append a suffix to a successful lookup.
default (see Section 33.4.1)
is still used if the lookup fails.
If a database was created with makemap's
(see Section 22.214.171.124) to include
the terminating zero byte with each key, this
-N switch may be specified to force all lookups to
also include a zero byte. Note that
-N is not needed for the
nis class and, if included, is ignored. See also
-O is specified,
sendmail uses an adaptive algorithm to decide
whether or not to look for the terminating zero byte.
The algorithm starts by accepting either. If the first key looked up
is found to end with a terminating zero byte, the algorithm
will thereafter look only for keys with terminating zero bytes.
If the first key that is looked up is found to not end with a terminating
zero byte, the algorithm will thereafter look only for keys without
terminating zero bytes.
-O switch is specified, sendmail never tries a zero byte, which
can speed matches.
Note that if both
-O are specified,
sendmail will never try to match at all,
thus causing all lookups to appear to fail.
Ordinarily, sendmail will complain if a database file cannot
be opened for reading. If the presence of a database file is optional
(as it may be on certain machines), the
switch should be used to tell sendmail that the database is optional.
Note that if a database is optional and cannot be opened, all lookups
will silently fail for rules that use that database.
"Bob \"bigboy\" Roberts \(esq\)"@bob.com
will have its nonescaped quotation marks removed to end up like this:
Bob "bigboy" Roberts (esq)@bob.com
Note that all escaped characters are de-escaped (have the backslash removed) during this process.
When quotation marks and escaped characters need to be preserved
in a key before it is looked up, you can use the
K configuration command. The
suppresses dequoting and de-escaping.
dequote class (see Section 33.8.4) refuses to
remove quotation marks if doing so will result in an illegal address.
For example, internal space characters are illegal in addresses:
"a b" becomes "a b"
-s switch causes all the quoted space characters to be
changed into a character that you specify just before the dequoting process.
Kdequote dequote -s+
Here, we specify that quoted strings will have quoted spaces converted into a plus before dequoting. Therefore, the above conversion becomes the following:
"a b" becomes a+b
The manner in which the key and its value are visually displayed
in flat, sequential, text files and certain network services, may not
be directly suitable for use in maps.
text class file, for example /etc/hosts,
may display the key on the right and the value on the left:
For such circumstances the
-v switch can be used with
K command to specify the column or item that will
be returned as the value when a key is matched. For example:
Kaddr text -k1 -v0 /etc/hosts
netinfo maps, the
-v switch specifies the
name (text) of the value's column.
-v switch specifies which column is the value to return. If it is
omitted, it defaults to 0 for the
text class and to
the last named column for the
Note that text columns are indexed beginning with 0 for the first
and 1 for the second. See also
-k (see Section 126.96.36.199)
for the key's column and
-z (see Section 188.8.131.52) for
the column delimiter.
184.108.40.206 here.our.domain /etc/hosts uses a whitespace nobody:*:65534:65534::/: /etc/passwd uses a colon
-z switch can be used to specify a delimiter whenever the
default delimiter of whitespace is not appropriate. In the case
of the /etc/passwd file, a database declaration might
look like this:
Kuid text -z: -k2 -v0 /etc/passwd # map to convert uid to login name