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Merge remote-tracking branch 'origin/topic/dnthayer/langref'

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* origin/topic/dnthayer/langref:
  Minor improvements to script language reference docs
  Add more script language reference documentation
  Split the types and attributes reference doc into two docs

Wow, this is great!

BIT-1269 #merged
This commit is contained in:
Robin Sommer 2014-10-07 14:18:08 -07:00
commit 175ff9cf2d
7 changed files with 1481 additions and 367 deletions
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7
doc/ext/bro.py
View file

@ -176,6 +176,10 @@ class BroIdentifier(BroGeneric):
def get_index_text(self, objectname, name):
return name
class BroKeyword(BroGeneric):
def get_index_text(self, objectname, name):
return name
class BroAttribute(BroGeneric):
def get_index_text(self, objectname, name):
return _('%s (attribute)') % (name)
@ -213,6 +217,7 @@ class BroDomain(Domain):
'type': ObjType(l_('type'), 'type'),
'namespace': ObjType(l_('namespace'), 'namespace'),
'id': ObjType(l_('id'), 'id'),
'keyword': ObjType(l_('keyword'), 'keyword'),
'enum': ObjType(l_('enum'), 'enum'),
'attr': ObjType(l_('attr'), 'attr'),
}
@ -221,6 +226,7 @@ class BroDomain(Domain):
'type': BroGeneric,
'namespace': BroNamespace,
'id': BroIdentifier,
'keyword': BroKeyword,
'enum': BroEnum,
'attr': BroAttribute,
}
@ -229,6 +235,7 @@ class BroDomain(Domain):
'type': XRefRole(),
'namespace': XRefRole(),
'id': XRefRole(),
'keyword': XRefRole(),
'enum': XRefRole(),
'attr': XRefRole(),
'see': XRefRole(),

232
doc/script-reference/attributes.rst Normal file
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@ -0,0 +1,232 @@
Attributes
==========
The Bro scripting language supports the following attributes.
+-----------------------------+-----------------------------------------------+
| Name | Description |
+=============================+===============================================+
| :bro:attr:`&redef` |Redefine a global constant or extend a type. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&priority` |Specify priority for event handler or hook. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&log` |Mark a record field as to be written to a log. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&optional` |Allow a record field value to be missing. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&default` |Specify a default value. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&add_func` |Specify a function to call for each "redef +=".|
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&delete_func` |Same as "&add_func", except for "redef -=". |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&expire_func` |Specify a function to call when container |
| |element expires. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&read_expire` |Specify a read timeout interval. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&write_expire` |Specify a write timeout interval. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&create_expire` |Specify a creation timeout interval. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&synchronized` |Synchronize a variable across nodes. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&persistent` |Make a variable persistent (written to disk). |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&rotate_interval`|Rotate a file after specified interval. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&rotate_size` |Rotate a file after specified file size. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&encrypt` |Encrypt a file when writing to disk. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&raw_output` |Open file in raw mode (chars. are not escaped).|
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&mergeable` |Prefer set union for synchronized state. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&group` |Group event handlers to activate/deactivate. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&error_handler` |Used internally for reporter framework events. |
+-----------------------------+-----------------------------------------------+
| :bro:attr:`&type_column` |Used by input framework for "port" type. |
+-----------------------------+-----------------------------------------------+
Here is a more detailed explanation of each attribute:
.. bro:attr:: &redef
Allows for redefinition of initial values of global objects declared as
constant.
In this example, the constant (assuming it is global) can be redefined
with a :bro:keyword:`redef` at some later point::
const clever = T &redef;
.. bro:attr:: &priority
Specifies the execution priority (as a signed integer) of a hook or
event handler. Higher values are executed before lower ones. The
default value is 0. Example::
event bro_init() &priority=10
{
print "high priority";
}
.. bro:attr:: &log
Writes a :bro:type:`record` field to the associated log stream.
.. bro:attr:: &optional
Allows a record field value to be missing (i.e., neither initialized nor
ever assigned a value).
In this example, the record could be instantiated with either
"myrec($a=127.0.0.1)" or "myrec($a=127.0.0.1, $b=80/tcp)"::
type myrec: record { a: addr; b: port &optional; };
The ``?$`` operator can be used to check if a record field has a value or
not (it returns a ``bool`` value of ``T`` if the field has a value,
and ``F`` if not).
.. bro:attr:: &default
Specifies a default value for a record field, container element, or a
function/hook/event parameter.
In this example, the record could be instantiated with either
"myrec($a=5, $c=3.14)" or "myrec($a=5, $b=53/udp, $c=3.14)"::
type myrec: record { a: count; b: port &default=80/tcp; c: double; };
In this example, the table will return the string ``"foo"`` for any
attempted access to a non-existing index::
global mytable: table[count] of string &default="foo";
When used with function/hook/event parameters, all of the parameters
with the "&default" attribute must come after all other parameters.
For example, the following function could be called either as "myfunc(5)"
or as "myfunc(5, 53/udp)"::
function myfunc(a: count, b: port &default=80/tcp)
{
print a, b;
}
.. bro:attr:: &add_func
Can be applied to an identifier with &redef to specify a function to
be called any time a "redef <id> += ..." declaration is parsed. The
function takes two arguments of the same type as the identifier, the first
being the old value of the variable and the second being the new
value given after the "+=" operator in the "redef" declaration. The
return value of the function will be the actual new value of the
variable after the "redef" declaration is parsed.
.. bro:attr:: &delete_func
Same as :bro:attr:`&add_func`, except for :bro:keyword:`redef` declarations
that use the "-=" operator.
.. bro:attr:: &expire_func
Called right before a container element expires. The function's
first parameter is of the same type of the container and the second
parameter the same type of the container's index. The return
value is an :bro:type:`interval` indicating the amount of additional
time to wait before expiring the container element at the given
index (which will trigger another execution of this function).
.. bro:attr:: &read_expire
Specifies a read expiration timeout for container elements. That is,
the element expires after the given amount of time since the last
time it has been read. Note that a write also counts as a read.
.. bro:attr:: &write_expire
Specifies a write expiration timeout for container elements. That
is, the element expires after the given amount of time since the
last time it has been written.
.. bro:attr:: &create_expire
Specifies a creation expiration timeout for container elements. That
is, the element expires after the given amount of time since it has
been inserted into the container, regardless of any reads or writes.
.. bro:attr:: &synchronized
Synchronizes variable accesses across nodes. The value of a
``&synchronized`` variable is automatically propagated to all peers
when it changes.
.. bro:attr:: &persistent
Makes a variable persistent, i.e., its value is written to disk (per
default at shutdown time).
.. bro:attr:: &rotate_interval
Rotates a file after a specified interval.
.. bro:attr:: &rotate_size
Rotates a file after it has reached a given size in bytes.
.. bro:attr:: &encrypt
Encrypts files right before writing them to disk.
.. bro:attr:: &raw_output
Opens a file in raw mode, i.e., non-ASCII characters are not
escaped.
.. bro:attr:: &mergeable
Prefers merging sets on assignment for synchronized state. This
attribute is used in conjunction with :bro:attr:`&synchronized`
container types: when the same container is updated at two peers
with different values, the propagation of the state causes a race
condition, where the last update succeeds. This can cause
inconsistencies and can be avoided by unifying the two sets, rather
than merely overwriting the old value.
.. bro:attr:: &group
Groups event handlers such that those in the same group can be
jointly activated or deactivated.
.. bro:attr:: &error_handler
Internally set on the events that are associated with the reporter
framework: :bro:id:`reporter_info`, :bro:id:`reporter_warning`, and
:bro:id:`reporter_error`. It prevents any handlers of those events
from being able to generate reporter messages that go through any of
those events (i.e., it prevents an infinite event recursion). Instead,
such nested reporter messages are output to stderr.
.. bro:attr:: &type_column
Used by the input framework. It can be used on columns of type
:bro:type:`port` (such a column only contains the port number) and
specifies the name of an additional column in
the input file which specifies the protocol of the port (tcp/udp/icmp).
In the following example, the input file would contain four columns
named "ip", "srcp", "proto", and "msg"::
type Idx: record {
ip: addr;
};
type Val: record {
srcp: port &type_column = "proto";
msg: string;
};

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doc/script-reference/directives.rst Normal file
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@ -0,0 +1,173 @@
Directives
==========
The Bro scripting language supports a number of directives that can
affect which scripts will be loaded or which lines in a script will be
executed. Directives are evaluated before script execution begins.
.. bro:keyword:: @DEBUG
TODO
.. bro:keyword:: @DIR
Expands to the directory pathname where the current script is located.
Example::
print "Directory:", @DIR;
.. bro:keyword:: @FILENAME
Expands to the filename of the current script.
Example::
print "File:", @FILENAME;
.. bro:keyword:: @load
Loads the specified Bro script, specified as the relative pathname
of the file (relative to one of the directories in Bro's file search path).
If the Bro script filename ends with ".bro", then you don't need to
specify the file extension. The filename cannot contain any whitespace.
In this example, Bro will try to load a script
"policy/misc/capture-loss.bro" by looking in each directory in the file
search path (the file search path can be changed by setting the BROPATH
environment variable)::
@load policy/misc/capture-loss
If you specify the name of a directory instead of a filename, then
Bro will try to load a file in that directory called "__load__.bro"
(presumably that file will contain additional "@load" directives).
In this example, Bro will try to load a file "tuning/defaults/__load__.bro"
by looking in each directory in the file search path::
@load tuning/defaults
The purpose of this directive is to ensure that all script dependencies
are satisfied, and to avoid having to list every needed Bro script
on the command-line. Bro keeps track of which scripts have been
loaded, so it is not an error to load a script more than once (once
a script has been loaded, any subsequent "@load" directives
for that script are ignored).
.. bro:keyword:: @load-sigs
This works similarly to "@load", except that in this case the filename
represents a signature file (not a Bro script). If the signature filename
ends with ".sig", then you don't need to specify the file extension
in the "@load-sigs" directive. The filename cannot contain any
whitespace.
In this example, Bro will try to load a signature file
"base/protocols/ssl/dpd.sig"::
@load-sigs base/protocols/ssl/dpd
The format for a signature file is explained in the documentation for the
`Signature Framework <../frameworks/signatures.html>`_.
.. bro:keyword:: @unload
This specifies a Bro script that we don't want to load (so a subsequent
attempt to load the specified script will be skipped). However,
if the specified script has already been loaded, then this directive
has no affect.
In the following example, if the "policy/misc/capture-loss.bro" script
has not been loaded yet, then Bro will not load it::
@unload policy/misc/capture-loss
.. bro:keyword:: @prefixes
Specifies a filename prefix to use when looking for script files
to load automatically. The prefix cannot contain any whitespace.
In the following example, the prefix "cluster" is used and all prefixes
that were previously specified are not used::
@prefixes = cluster
In the following example, the prefix "cluster-manager" is used in
addition to any previously-specified prefixes::
@prefixes += cluster-manager
The way this works is that after Bro parses all script files, then for each
loaded script Bro will take the absolute path of the script and then
it removes the portion of the directory path that is in Bro's file
search path. Then it replaces each "/" character with a period "."
and then prepends the prefix (specified in the "@prefixes" directive)
followed by a period. The resulting filename is searched for in each
directory in Bro's file search path. If a matching file is found, then
the file is automatically loaded.
For example, if a script called "local.bro" has been loaded, and a prefix
of "test" was specified, then Bro will look for a file named
"test.local.bro" in each directory of Bro's file search path.
An alternative way to specify prefixes is to use the "-p" Bro
command-line option.
.. bro:keyword:: @if
The specified expression must evaluate to type :bro:type:`bool`. If the
value is true, then the following script lines (up to the next "@else"
or "@endif") are available to be executed.
Example::
@if ( ver == 2 )
print "version 2 detected";
@endif
.. bro:keyword:: @ifdef
This works like "@if", except that the result is true if the specified
identifier is defined.
Example::
@ifdef ( pi )
print "pi is defined";
@endif
.. bro:keyword:: @ifndef
This works exactly like "@ifdef", except that the result is true if the
specified identifier is not defined.
Example::
@ifndef ( pi )
print "pi is not defined";
@endif
.. bro:keyword:: @else
This directive is optional after an "@if", "@ifdef", or
"@ifndef". If present, it provides an else clause.
Example::
@ifdef ( pi )
print "pi is defined";
@else
print "pi is not defined";
@endif
.. bro:keyword:: @endif
This directive is required to terminate each "@if", "@ifdef", or
"@ifndef".

6
doc/script-reference/index.rst
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@ -5,10 +5,14 @@ Script Reference
.. toctree::
:maxdepth: 1
operators
types
attributes
statements
directives
notices
proto-analyzers
file-analyzers
builtins
packages
scripts
Broxygen Example Script </scripts/broxygen/example.bro>

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@ -0,0 +1,191 @@
Operators
=========
The Bro scripting language supports the following operators. Note that
each data type only supports a subset of these operators. For more
details, see the documentation about the `data types <types.html>`_.
Relational operators
--------------------
The relational operators evaluate to type :bro:type:`bool`.
+------------------------------+--------------+
| Name | Syntax |
+==============================+==============+
| Equality | *a* == *b* |
+------------------------------+--------------+
| Inequality | *a* != *b* |
+------------------------------+--------------+
| Less than | *a* < *b* |
+------------------------------+--------------+
| Less than or equal | *a* <= *b* |
+------------------------------+--------------+
| Greater than | *a* > *b* |
+------------------------------+--------------+
| Greater than or equal | *a* >= *b* |
+------------------------------+--------------+
Logical operators
-----------------
The logical operators require operands of type :bro:type:`bool`, and
evaluate to type :bro:type:`bool`.
+------------------------------+--------------+
| Name | Syntax |
+==============================+==============+
| Logical AND | *a* && *b* |
+------------------------------+--------------+
| Logical OR | *a* \|\| *b* |
+------------------------------+--------------+
| Logical NOT | ! *a* |
+------------------------------+--------------+
Arithmetic operators
--------------------
+------------------------------+-------------+-------------------------------+
| Name | Syntax | Notes |
+==============================+=============+===============================+
| Addition | *a* + *b* | For :bro:type:`string` |
| | | operands, this performs |
| | | string concatenation. |
+------------------------------+-------------+-------------------------------+
| Subtraction | *a* - *b* | |
+------------------------------+-------------+-------------------------------+
| Multiplication | *a* \* *b* | |
+------------------------------+-------------+-------------------------------+
| Division | *a* / *b* | For :bro:type:`int` or |
| | | :bro:type:`count` operands, |
| | | the fractional part of the |
| | | result is dropped. |
+------------------------------+-------------+-------------------------------+
| Modulo | *a* % *b* | Operand types cannot be |
| | | "double". |
+------------------------------+-------------+-------------------------------+
| Unary plus | \+ *a* | |
+------------------------------+-------------+-------------------------------+
| Unary minus | \- *a* | |
+------------------------------+-------------+-------------------------------+
| Pre-increment | ++ *a* | Operand type cannot be |
| | | "double". |
+------------------------------+-------------+-------------------------------+
| Pre-decrement | ``--`` *a* | Operand type cannot be |
| | | "double". |
+------------------------------+-------------+-------------------------------+
| Absolute value | \| *a* \| | If operand is |
| | | :bro:type:`string`, |
| | | :bro:type:`set`, |
| | | :bro:type:`table`, or |
| | | :bro:type:`vector`, this |
| | | evaluates to number |
| | | of elements. |
+------------------------------+-------------+-------------------------------+
Assignment operators
--------------------
The assignment operators evaluate to the result of the assignment.
+------------------------------+-------------+
| Name | Syntax |
+==============================+=============+
| Assignment | *a* = *b* |
+------------------------------+-------------+
| Addition assignment | *a* += *b* |
+------------------------------+-------------+
| Subtraction assignment | *a* -= *b* |
+------------------------------+-------------+
Record field operators
----------------------
The record field operators take a :bro:type:`record` as the first operand,
and a field name as the second operand. For both operators, the specified
field name must be in the declaration of the record type.
+------------------------------+-------------+-------------------------------+
| Name | Syntax | Notes |
+==============================+=============+===============================+
| Field access | *a* $ *b* | |
+------------------------------+-------------+-------------------------------+
| Field value existence test | *a* ?$ *b* | Evaluates to type |
| | | :bro:type:`bool`. |
| | | True if the specified field |
| | | has been assigned a value, or |
| | | false if not. |
+------------------------------+-------------+-------------------------------+
Other operators
---------------
+--------------------------------+-------------------+------------------------+
| Name | Syntax | Notes |
+================================+===================+========================+
| Membership test | *a* in *b* |Evaluates to type |
| | |:bro:type:`bool`. Do not|
| | |confuse this use of "in"|
| | |with that used in a |
| | |:bro:keyword:`for` |
| | |statement. |
+--------------------------------+-------------------+------------------------+
| Non-membership test | *a* !in *b* |This is the logical NOT |
| | |of the "in" operator. |
| | |For example: "a !in b" |
| | |is equivalent to |
| | |"!(a in b)". |
+--------------------------------+-------------------+------------------------+
| Table or vector element access | *a* [ *b* ] |This operator can also |
| | |be used with a |
| | |:bro:type:`set`, but |
| | |only with the |
| | |:bro:keyword:`add` or |
| | |:bro:keyword:`delete` |
| | |statement. |
+--------------------------------+-------------------+------------------------+
| Substring extraction | *a* [ *b* : *c* ] |See the |
| | |:bro:type:`string` type |
| | |for more details. |
+--------------------------------+-------------------+------------------------+
| Create a deep copy | copy ( *a* ) |This is relevant only |
| | |for data types that are |
| | |assigned by reference, |
| | |such as |
| | |:bro:type:`vector`, |
| | |:bro:type:`set`, |
| | |:bro:type:`table`, |
| | |and :bro:type:`record`. |
+--------------------------------+-------------------+------------------------+
| Module namespace access | *a* \:\: *b* |The first operand is the|
| | |module name, and the |
| | |second operand is an |
| | |identifier that refers |
| | |to a global variable, |
| | |enumeration constant, or|
| | |user-defined type that |
| | |was exported from the |
| | |module. |
+--------------------------------+-------------------+------------------------+
| Conditional | *a* ? *b* : *c* |The first operand must |
| | |evaluate to type |
| | |:bro:type:`bool`. |
| | |If true, then the |
| | |second expression is |
| | |evaluated and is the |
| | |result of the entire |
| | |expression. Otherwise, |
| | |the third expression is |
| | |evaluated and is the |
| | |result of the entire |
| | |expression. The types of|
| | |the second and third |
| | |operands must be |
| | |compatible. |
+--------------------------------+-------------------+------------------------+

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@ -0,0 +1,602 @@
Declarations and Statements
===========================
The Bro scripting language supports the following declarations and
statements.
Declarations
~~~~~~~~~~~~
+----------------------------+-----------------------------+
| Name | Description |
+============================+=============================+
| :bro:keyword:`module` | Change the current module |
+----------------------------+-----------------------------+
| :bro:keyword:`export` | Export identifiers from the |
| | current module |
+----------------------------+-----------------------------+
| :bro:keyword:`global` | Declare a global variable |
+----------------------------+-----------------------------+
| :bro:keyword:`const` | Declare a constant |
+----------------------------+-----------------------------+
| :bro:keyword:`type` | Declare a user-defined type |
+----------------------------+-----------------------------+
| :bro:keyword:`redef` | Redefine a global value or |
| | extend a user-defined type |
+----------------------------+-----------------------------+
| `function/event/hook`_ | Declare a function, event |
| | handler, or hook |
+----------------------------+-----------------------------+
Statements
~~~~~~~~~~
+----------------------------+------------------------+
| Name | Description |
+============================+========================+
| :bro:keyword:`local` | Declare a local |
| | variable |
+----------------------------+------------------------+
| :bro:keyword:`add`, | Add or delete |
| :bro:keyword:`delete` | elements |
+----------------------------+------------------------+
| :bro:keyword:`print` | Print to stdout or a |
| | file |
+----------------------------+------------------------+
| :bro:keyword:`for`, | Loop over each |
| :bro:keyword:`next`, | element in a container |
| :bro:keyword:`break` | object |
+----------------------------+------------------------+
| :bro:keyword:`if` | Evaluate boolean |
| | expression and if true,|
| | execute a statement |
+----------------------------+------------------------+
| :bro:keyword:`switch`, | Evaluate expression |
| :bro:keyword:`break`, | and execute statement |
| :bro:keyword:`fallthrough` | with a matching value |
+----------------------------+------------------------+
| :bro:keyword:`when` | Asynchronous execution |
+----------------------------+------------------------+
| :bro:keyword:`event`, | Invoke or schedule |
| :bro:keyword:`schedule` | an event handler |
+----------------------------+------------------------+
| :bro:keyword:`return` | Return from function, |
| | hook, or event handler |
+----------------------------+------------------------+
Declarations
------------
The following global declarations cannot occur within a function, hook, or
event handler. Also, these declarations cannot appear after any statements
that are outside of a function, hook, or event handler.
.. bro:keyword:: module
The "module" keyword is used to change the current module. This
affects the scope of any subsequently declared global identifiers.
Example::
module mymodule;
If a global identifier is declared after a "module" declaration,
then its scope ends at the end of the current Bro script or at the
next "module" declaration, whichever comes first. However, if a
global identifier is declared after a "module" declaration, but inside
an :bro:keyword:`export` block, then its scope ends at the end of the
last loaded Bro script, but it must be referenced using the namespace
operator (``::``) in other modules.
There can be any number of "module" declarations in a Bro script.
The same "module" declaration can appear in any number of different
Bro scripts.
.. bro:keyword:: export
An "export" block contains one or more declarations
(no statements are allowed in an "export" block) that the current
module is exporting. This enables these global identifiers to be visible
in other modules (but not prior to their declaration) via the namespace
operator (``::``). See the :bro:keyword:`module` keyword for a more
detailed explanation.
Example::
export {
redef enum Log::ID += { LOG };
type Info: record {
ts: time &log;
uid: string &log;
};
const conntime = 30sec &redef;
}
Note that the braces in an "export" block are always required
(they do not indicate a compound statement). Also, no semicolon is
needed to terminate an "export" block.
.. bro:keyword:: global
Variables declared with the "global" keyword will be global.
If a type is not specified, then an initializer is required so that
the type can be inferred. Likewise, if an initializer is not supplied,
then the type must be specified. Example::
global pi = 3.14;
global hosts: set[addr];
global ciphers: table[string] of string = table();
Variable declarations outside of any function, hook, or event handler are
required to use this keyword (unless they are declared with the
:bro:keyword:`const` keyword). Definitions of functions, hooks, and
event handlers are not allowed to use the "global"
keyword (they already have global scope), except function declarations
where no function body is supplied use the "global" keyword.
The scope of a global variable begins where the declaration is located,
and extends through all remaining Bro scripts that are loaded (however,
see the :bro:keyword:`module` keyword for an explanation of how modules
change the visibility of global identifiers).
.. bro:keyword:: const
A variable declared with the "const" keyword will be constant.
Variables declared as constant are required to be initialized at the
time of declaration. Example::
const pi = 3.14;
const ssh_port: port = 22/tcp;
The value of a constant cannot be changed later (the only
exception is if the variable is global and has the :bro:attr:`&redef`
attribute, then its value can be changed only with a :bro:keyword:`redef`).
The scope of a constant is local if the declaration is in a
function, hook, or event handler, and global otherwise.
Note that the "const" keyword cannot be used with either the "local"
or "global" keywords (i.e., "const" replaces "local" and "global").
.. bro:keyword:: type
The "type" keyword is used to declare a user-defined type. The name
of this new type has global scope and can be used anywhere a built-in
type name can occur.
The "type" keyword is most commonly used when defining a
:bro:type:`record` or an :bro:type:`enum`, but is also useful when
dealing with more complex types.
Example::
type mytype: table[count] of table[addr, port] of string;
global myvar: mytype;
.. bro:keyword:: redef
There are three ways that "redef" can be used: to change the value of
a global variable, to extend a record type or enum type, or to specify
a new event handler body that replaces all those that were previously
defined.
If you're using "redef" to change a global variable (defined using either
:bro:keyword:`const` or :bro:keyword:`global`), then the variable that you
want to change must have the :bro:attr:`&redef` attribute. If the variable
you're changing is a table, set, or pattern, you can use ``+=`` to add
new elements, or you can use ``=`` to specify a new value (all previous
contents of the object are removed). If the variable you're changing is a
set or table, then you can use the ``-=`` operator to remove the
specified elements (nothing happens for specified elements that don't
exist). If the variable you are changing is not a table, set, or pattern,
then you must use the ``=`` operator.
Examples::
redef pi = 3.14;
If you're using "redef" to extend a record or enum, then you must
use the ``+=`` assignment operator.
For an enum, you can add more enumeration constants, and for a record
you can add more record fields (however, each record field in the "redef"
must have either the :bro:attr:`&optional` or :bro:attr:`&default`
attribute).
Examples::
redef enum color += { Blue, Red };
redef record MyRecord += { n2:int &optional; s2:string &optional; };
If you're using "redef" to specify a new event handler body that
replaces all those that were previously defined (i.e., any subsequently
defined event handler body will not be affected by this "redef"), then
the syntax is the same as a regular event handler definition except for
the presence of the "redef" keyword.
Example::
redef event myevent(s:string) { print "Redefined", s; }
.. _function/event/hook:
**function/event/hook**
For details on how to declare a :bro:type:`function`,
:bro:type:`event` handler, or :bro:type:`hook`,
see the documentation for those types.
Statements
----------
Each statement in a Bro script must be terminated with a semicolon (with a
few exceptions noted below). An individual statement can span multiple
lines.
All statements (except those contained within a function, hook, or event
handler) must appear after all global declarations.
Here are the statements that the Bro scripting language supports.
.. bro:keyword:: add
The "add" statement is used to add an element to a :bro:type:`set`.
Nothing happens if the specified element already exists in the set.
Example::
local myset: set[string];
add myset["test"];
.. bro:keyword:: break
The "break" statement is used to break out of a :bro:keyword:`switch` or
:bro:keyword:`for` statement.
.. bro:keyword:: delete
The "delete" statement is used to remove an element from a
:bro:type:`set` or :bro:type:`table`. Nothing happens if the
specified element does not exist in the set or table.
Example::
local myset = set("this", "test");
local mytable = table(["key1"] = 80/tcp, ["key2"] = 53/udp);
delete myset["test"];
delete mytable["key1"];
.. bro:keyword:: event
The "event" statement immediately queues invocation of an event handler.
Example::
event myevent("test", 5);
.. bro:keyword:: fallthrough
The "fallthrough" statement can be used as the last statement in a
"case" block to indicate that execution should continue into the
next "case" or "default" label.
For an example, see the :bro:keyword:`switch` statement.
.. bro:keyword:: for
A "for" loop iterates over each element in a string, set, vector, or
table and executes a statement for each iteration.
For each iteration of the loop, a loop variable will be assigned to an
element if the expression evaluates to a string or set, or an index if
the expression evaluates to a vector or table. Then the statement
is executed. However, the statement will not be executed if the expression
evaluates to an object with no elements.
If the expression is a table or a set with more than one index, then the
loop variable must be specified as a comma-separated list of different
loop variables (one for each index), enclosed in brackets.
A :bro:keyword:`break` statement can be used at any time to immediately
terminate the "for" loop, and a :bro:keyword:`next` statement can be
used to skip to the next loop iteration.
Note that the loop variable in a "for" statement is not allowed to be
a global variable, and it does not need to be declared prior to the "for"
statement. The type will be inferred from the elements of the
expression.
Example::
local myset = set(80/tcp, 81/tcp);
local mytable = table([10.0.0.1, 80/tcp]="s1", [10.0.0.2, 81/tcp]="s2");
for (p in myset)
print p;
for ([i,j] in mytable) {
if (mytable[i,j] == "done")
break;
if (mytable[i,j] == "skip")
next;
print i,j;
}
.. bro:keyword:: if
Evaluates a given expression, which must yield a :bro:type:`bool` value.
If true, then a specified statement is executed. If false, then
the statement is not executed. Example::
if ( x == 2 ) print "x is 2";
However, if the expression evaluates to false and if an "else" is
provided, then the statement following the "else" is executed. Example::
if ( x == 2 )
print "x is 2";
else
print "x is not 2";
.. bro:keyword:: local
A variable declared with the "local" keyword will be local. If a type
is not specified, then an initializer is required so that the type can
be inferred. Likewise, if an initializer is not supplied, then the
type must be specified.
Examples::
local x1 = 5.7;
local x2: double;
local x3: double = 5.7;
Variable declarations inside a function, hook, or event handler are
required to use this keyword (the only two exceptions are variables
declared with :bro:keyword:`const`, and variables implicitly declared in a
:bro:keyword:`for` statement).
The scope of a local variable starts at the location where it is declared
and persists to the end of the function, hook,
or event handler in which it is declared (this is true even if the
local variable was declared within a `compound statement`_ or is the loop
variable in a "for" statement).
.. bro:keyword:: next
The "next" statement can only appear within a :bro:keyword:`for` loop.
It causes execution to skip to the next iteration.
For an example, see the :bro:keyword:`for` statement.
.. bro:keyword:: print
The "print" statement takes a comma-separated list of one or more
expressions. Each expression in the list is evaluated and then converted
to a string. Then each string is printed, with each string separated by
a comma in the output.
Examples::
print 3.14;
print "Results", x, y;
By default, the "print" statement writes to the standard
output (stdout). However, if the first expression is of type
:bro:type:`file`, then "print" writes to that file.
If a string contains non-printable characters (i.e., byte values that are
not in the range 32 - 126), then the "print" statement converts each
non-printable character to an escape sequence before it is printed.
For more control over how the strings are formatted, see the :bro:id:`fmt`
function.
.. bro:keyword:: return
The "return" statement immediately exits the current function, hook, or
event handler. For a function, the specified expression (if any) is
evaluated and returned. A "return" statement in a hook or event handler
cannot return a value because event handlers and hooks do not have
return types.
Examples::
function my_func(): string
{
return "done";
}
event my_event(n: count)
{
if ( n == 0 ) return;
print n;
}
There is a special form of the "return" statement that is only allowed
in functions. Syntactically, it looks like a :bro:keyword:`when` statement
immediately preceded by the "return" keyword. This form of the "return"
statement is used to specify a function that delays its result (such a
function can only be called in the expression of a :bro:keyword:`when`
statement). The function returns at the time the "when"
statement's condition becomes true, and the function returns the value
that the "when" statement's body returns (or if the condition does
not become true within the specified timeout interval, then the function
returns the value that the "timeout" block returns).
Example::
global X: table[string] of count;
function a() : count
{
# This delays until condition becomes true.
return when ( "a" in X )
{
return X["a"];
}
timeout 30 sec
{
return 0;
}
}
event bro_init()
{
# Installs a trigger which fires if a() returns 42.
when ( a() == 42 )
print "expected result";
print "Waiting for a() to return...";
X["a"] = 42;
}
.. bro:keyword:: schedule
The "schedule" statement is used to raise a specified event with
specified parameters at a later time specified as an :bro:type:`interval`.
Example::
schedule 30sec { myevent(x, y, z) };
Note that the braces are always required (they do not indicate a
`compound statement`_).
Note that "schedule" is actually an expression that returns a value
of type "timer", but in practice the return value is not used.
.. bro:keyword:: switch
A "switch" statement evaluates a given expression and jumps to
the first "case" label which contains a matching value (the result of the
expression must be type-compatible with all of the values in all of the
"case" labels). If there is no matching value, then execution jumps to
the "default" label instead, and if there is no "default" label then
execution jumps out of the "switch" block.
Here is an example (assuming that "get_day_of_week" is a
function that returns a string)::
switch get_day_of_week()
{
case "Sa", "Su":
print "weekend";
fallthrough;
case "Mo", "Tu", "We", "Th", "Fr":
print "valid result";
break;
default:
print "invalid result";
break;
}
A "switch" block can have any number of "case" labels, and one
optional "default" label.
A "case" label can have a comma-separated list of
more than one value. A value in a "case" label can be an expression,
but it must be a constant expression (i.e., the expression can consist
only of constants).
Each "case" and the "default" block must
end with either a :bro:keyword:`break`, :bro:keyword:`fallthrough`, or
:bro:keyword:`return` statement (although "return" is allowed only
if the "switch" statement is inside a function, hook, or event handler).
If a "case" (or "default") block contain more than one statement, then
there is no need to wrap them in braces.
Note that the braces in a "switch" statement are always required (these
do not indicate the presence of a `compound statement`_), and that no
semicolon is needed at the end of a "switch" statement.
.. bro:keyword:: when
Evaluates a given expression, which must result in a value of type
:bro:type:`bool`. When the value of the expression becomes available
and if the result is true, then a specified statement is executed.
In the following example, if the expression evaluates to true, then
the "print" statement is executed::
when ( (local x = foo()) && x == 42 )
print x;
However, if a timeout is specified, and if the expression does not
evaluate to true within the specified timeout interval, then the
statement following the "timeout" keyword is executed::
when ( (local x = foo()) && x == 42 )
print x;
timeout 5sec {
print "timeout";
}
Note that when a timeout is specified the braces are
always required (these do not indicate a `compound statement`_).
The expression in a "when" statement can contain a declaration of a local
variable but only if the declaration is written in the form
"local *var* = *init*" (example: "local x = myfunction()"). This form
of a local declaration is actually an expression, the result of which
is always a boolean true value.
The expression in a "when" statement can contain an asynchronous function
call such as :bro:id:`lookup_hostname` (in fact, this is the only place
such a function can be called), but it can also contain an ordinary
function call. When an asynchronous function call is in the expression,
then Bro will continue processing statements in the script following
the "when" statement, and when the result of the function call is available
Bro will finish evaluating the expression in the "when" statement.
See the :bro:keyword:`return` statement for an explanation of how to
create an asynchronous function in a Bro script.
.. _compound statement:
**compound statement**
A compound statement is created by wrapping zero or more statements in
braces ``{ }``. Individual statements inside the braces need to be
terminated by a semicolon, but a semicolon is not needed at the end
(outside of the braces) of a compound statement.
A compound statement is required in order to execute more than one
statement in the body of a :bro:keyword:`for`, :bro:keyword:`if`, or
:bro:keyword:`when` statement.
Example::
if ( x == 2 ) {
print "x is 2";
++x;
}
Note that there are other places in the Bro scripting language that use
braces, but that do not indicate the presence of a compound
statement (these are noted in the documentation).
.. _null:
**null statement**
The null statement (executing it has no effect) consists of just a
semicolon. This might be useful during testing or debugging a Bro script
in places where a statement is required, but it is probably not useful
otherwise.
Example::
if ( x == 2 )
;

637
doc/script-reference/builtins.rst → doc/script-reference/types.rst
View file

@ -1,106 +1,128 @@
Types and Attributes
====================
Types
-----
=====
Every value in a Bro script has a type (see below for a list of all built-in
types). Although Bro variables have static types (meaning that their type
is fixed), their type is inferred from the value to which they are
initially assigned when the variable is declared without an explicit type
name.
The Bro scripting language supports the following built-in types:
Automatic conversions happen when a binary operator has operands of
different types. Automatic conversions are limited to converting between
numeric types. The numeric types are ``int``, ``count``, and ``double``
(``bool`` is not a numeric type).
When an automatic conversion occurs, values are promoted to the "highest"
type in the expression. In general, this promotion follows a simple
hierarchy: ``double`` is highest, ``int`` comes next, and ``count`` is
lowest.
+-----------------------+--------------------+
| Name | Description |
+=======================+====================+
| :bro:type:`bool` | Boolean |
+-----------------------+--------------------+
| :bro:type:`count`, | Numeric types |
| :bro:type:`int`, | |
| :bro:type:`double` | |
+-----------------------+--------------------+
| :bro:type:`time`, | Time types |
| :bro:type:`interval` | |
+-----------------------+--------------------+
| :bro:type:`string` | String |
+-----------------------+--------------------+
| :bro:type:`pattern` | Regular expression |
+-----------------------+--------------------+
| :bro:type:`port`, | Network types |
| :bro:type:`addr`, | |
| :bro:type:`subnet` | |
+-----------------------+--------------------+
| :bro:type:`enum` | Enumeration |
| | (user-defined type)|
+-----------------------+--------------------+
| :bro:type:`table`, | Container types |
| :bro:type:`set`, | |
| :bro:type:`vector`, | |
| :bro:type:`record` | |
+-----------------------+--------------------+
| :bro:type:`function`, | Executable types |
| :bro:type:`event`, | |
| :bro:type:`hook` | |
+-----------------------+--------------------+
| :bro:type:`file` | File type (only |
| | for writing) |
+-----------------------+--------------------+
| :bro:type:`opaque` | Opaque type (for |
| | some built-in |
| | functions) |
+-----------------------+--------------------+
| :bro:type:`any` | Any type (for |
| | functions or |
| | containers) |
+-----------------------+--------------------+
The Bro scripting language supports the following built-in types.
.. bro:type:: void
An internal Bro type (i.e., "void" is not a reserved keyword in the Bro
scripting language) representing the absence of a return type for a
function.
Here is a more detailed description of each type:
.. bro:type:: bool
Reflects a value with one of two meanings: true or false. The two
``bool`` constants are ``T`` and ``F``.
"bool" constants are ``T`` and ``F``.
The ``bool`` type supports the following operators: equality/inequality
The "bool" type supports the following operators: equality/inequality
(``==``, ``!=``), logical and/or (``&&``, ``||``), logical
negation (``!``), and absolute value (where ``|T|`` is 1, and ``|F|`` is 0).
negation (``!``), and absolute value (where ``|T|`` is 1, and ``|F|`` is 0,
and in both cases the result type is :bro:type:`count`).
.. bro:type:: int
A numeric type representing a 64-bit signed integer. An ``int`` constant
is a string of digits preceded by a ``+`` or ``-`` sign, e.g.
A numeric type representing a 64-bit signed integer. An "int" constant
is a string of digits preceded by a "+" or "-" sign, e.g.
``-42`` or ``+5`` (the "+" sign is optional but see note about type
inferencing below). An ``int`` constant can also be written in
inferencing below). An "int" constant can also be written in
hexadecimal notation (in which case "0x" must be between the sign and
the hex digits), e.g. ``-0xFF`` or ``+0xabc123``.
The ``int`` type supports the following operators: arithmetic
The "int" type supports the following operators: arithmetic
operators (``+``, ``-``, ``*``, ``/``, ``%``), comparison operators
(``==``, ``!=``, ``<``, ``<=``, ``>``, ``>=``), assignment operators
(``=``, ``+=``, ``-=``), pre-increment (``++``), pre-decrement
(``--``), and absolute value (e.g., ``|-3|`` is 3).
(``--``), unary plus and minus (``+``, ``-``), and absolute value
(e.g., ``|-3|`` is 3, but the result type is :bro:type:`count`).
When using type inferencing use care so that the
intended type is inferred, e.g. ``local size_difference = 0`` will
infer :bro:type:`count`, while ``local size_difference = +0``
will infer :bro:type:`int`.
intended type is inferred, e.g. "local size_difference = 0" will
infer ":bro:type:`count`", while "local size_difference = +0"
will infer "int".
.. bro:type:: count
A numeric type representing a 64-bit unsigned integer. A ``count``
constant is a string of digits, e.g. ``1234`` or ``0``. A ``count``
A numeric type representing a 64-bit unsigned integer. A "count"
constant is a string of digits, e.g. ``1234`` or ``0``. A "count"
can also be written in hexadecimal notation (in which case "0x" must
precede the hex digits), e.g. ``0xff`` or ``0xABC123``.
The ``count`` type supports the same operators as the :bro:type:`int`
type. A unary plus or minus applied to a ``count`` results in an ``int``.
.. bro:type:: counter
An alias to :bro:type:`count`.
The "count" type supports the same operators as the ":bro:type:`int`"
type, but a unary plus or minus applied to a "count" results in an
"int".
.. bro:type:: double
A numeric type representing a double-precision floating-point
number. Floating-point constants are written as a string of digits
with an optional decimal point, optional scale-factor in scientific
notation, and optional ``+`` or ``-`` sign. Examples are ``-1234``,
notation, and optional "+" or "-" sign. Examples are ``-1234``,
``-1234e0``, ``3.14159``, and ``.003E-23``.
The ``double`` type supports the following operators: arithmetic
The "double" type supports the following operators: arithmetic
operators (``+``, ``-``, ``*``, ``/``), comparison operators
(``==``, ``!=``, ``<``, ``<=``, ``>``, ``>=``), assignment operators
(``=``, ``+=``, ``-=``), and absolute value (e.g., ``|-3.14|`` is 3.14).
(``=``, ``+=``, ``-=``), unary plus and minus (``+``, ``-``), and
absolute value (e.g., ``|-3.14|`` is 3.14).
When using type inferencing use care so that the
intended type is inferred, e.g. ``local size_difference = 5`` will
infer :bro:type:`count`, while ``local size_difference = 5.0``
will infer :bro:type:`double`.
intended type is inferred, e.g. "local size_difference = 5" will
infer ":bro:type:`count`", while "local size_difference = 5.0"
will infer "double".
.. bro:type:: time
A temporal type representing an absolute time. There is currently
no way to specify a ``time`` constant, but one can use the
:bro:id:`double_to_time`, :bro:id:`current_time`, or :bro:id:`network_time`
built-in functions to assign a value to a ``time``-typed variable.
built-in functions to assign a value to a ``time``-typed variable.
Time values support the comparison operators (``==``, ``!=``, ``<``,
``<=``, ``>``, ``>=``). A ``time`` value can be subtracted from
another ``time`` value to produce an ``interval`` value. An ``interval``
value can be added to, or subtracted from, a ``time`` value to produce a
``time`` value. The absolute value of a ``time`` value is a ``double``
with the same numeric value.
another ``time`` value to produce an :bro:type:`interval` value. An
``interval`` value can be added to, or subtracted from, a ``time`` value
to produce a ``time`` value. The absolute value of a ``time`` value is
a :bro:type:`double` with the same numeric value.
.. bro:type:: interval
@ -115,52 +137,58 @@ The Bro scripting language supports the following built-in types.
``3.5mins``. An ``interval`` can also be negated, for example
``-12 hr`` represents "twelve hours in the past".
Intervals support addition and subtraction. Intervals also support
division (in which case the result is a ``double`` value), the
comparison operators (``==``, ``!=``, ``<``, ``<=``, ``>``, ``>=``),
and the assignment operators (``=``, ``+=``, ``-=``). Also, an
``interval`` can be multiplied or divided by an arithmetic type
(``count``, ``int``, or ``double``) to produce an ``interval`` value.
The absolute value of an ``interval`` is a ``double`` value equal to the
number of seconds in the ``interval`` (e.g., ``|-1 min|`` is 60).
Intervals support addition and subtraction, the comparison operators
(``==``, ``!=``, ``<``, ``<=``, ``>``, ``>=``), the assignment
operators (``=``, ``+=``, ``-=``), and unary plus and minus (``+``, ``-``).
Intervals also support division (in which case the result is a
:bro:type:`double` value). An ``interval`` can be multiplied or divided
by an arithmetic type (``count``, ``int``, or ``double``) to produce
an ``interval`` value. The absolute value of an ``interval`` is a
``double`` value equal to the number of seconds in the ``interval``
(e.g., ``|-1 min|`` is 60.0).
.. bro:type:: string
A type used to hold character-string values which represent text.
String constants are created by enclosing text in double quotes (")
and the backslash character (\\) introduces escape sequences (all of
the C-style escape sequences are supported).
A type used to hold character-string values which represent text, although
strings in a Bro script can actually contain any arbitrary binary data.
String constants are created by enclosing text within a pair of double
quotes ("). A string constant cannot span multiple lines in a Bro script.
The backslash character (\\) introduces escape sequences. The
following escape sequences are recognized: ``\n``, ``\t``, ``\v``, ``\b``,
``\r``, ``\f``, ``\a``, ``\ooo`` (where each 'o' is an octal digit),
``\xhh`` (where each 'h' is a hexadecimal digit). For escape sequences
that don't match any of these, Bro will just remove the backslash (so
to represent a literal backslash in a string constant, you just use
two consecutive backslashes).
Strings support concatenation (``+``), and assignment (``=``, ``+=``).
Strings also support the comparison operators (``==``, ``!=``, ``<``,
``<=``, ``>``, ``>=``). The number of characters in a string can be
found by enclosing the string within pipe characters (e.g., ``|"abc"|``
is 3).
The subscript operator can extract an individual character or a substring
of a string (string indexing is zero-based, but an index of
-1 refers to the last character in the string, and -2 refers to the
second-to-last character, etc.). When extracting a substring, the
starting and ending index values are separated by a colon. For example::
local orig = "0123456789";
local third_char = orig[2];
local last_char = orig[-1];
local first_three_chars = orig[0:2];
Substring searching can be performed using the "in" or "!in"
is 3). Substring searching can be performed using the "in" or "!in"
operators (e.g., "bar" in "foobar" yields true).
Note that Bro represents strings internally as a count and vector of
bytes rather than a NUL-terminated byte string (although string
constants are also automatically NUL-terminated). This is because
network traffic can easily introduce NULs into strings either by
nature of an application, inadvertently, or maliciously. And while
NULs are allowed in Bro strings, when present in strings passed as
arguments to many functions, a run-time error can occur as their
presence likely indicates a sort of problem. In that case, the
string will also only be represented to the user as the literal
"<string-with-NUL>" string.
The subscript operator can extract a substring of a string. To do this,
specify the starting index to extract (if the starting index is omitted,
then zero is assumed), followed by a colon and index
one past the last character to extract (if the last index is omitted,
then the extracted substring will go to the end of the original string).
However, if both the colon and last index are omitted, then a string of
length one is extracted. String indexing is zero-based, but an index
of -1 refers to the last character in the string, and -2 refers to the
second-to-last character, etc. Here are a few examples::
local orig = "0123456789";
local second_char = orig[1];
local last_char = orig[-1];
local first_two_chars = orig[:2];
local last_two_chars = orig[8:];
local no_first_and_last = orig[1:9];
Note that the subscript operator cannot be used to modify a string (i.e.,
it cannot be on the left side of an assignment operator).
.. bro:type:: pattern
@ -174,7 +202,7 @@ The Bro scripting language supports the following built-in types.
and embedded.
In exact matching the ``==`` equality relational operator is used
with one :bro:type:`pattern` operand and one :bro:type:`string`
with one "pattern" operand and one ":bro:type:`string`"
operand (order of operands does not matter) to check whether the full
string exactly matches the pattern. In exact matching, the ``^``
beginning-of-line and ``$`` end-of-line anchors are redundant since
@ -190,8 +218,8 @@ The Bro scripting language supports the following built-in types.
yields false. The ``!=`` operator would yield the negation of ``==``.
In embedded matching the ``in`` operator is used with one
:bro:type:`pattern` operand (which must be on the left-hand side) and
one :bro:type:`string` operand, but tests whether the pattern
"pattern" operand (which must be on the left-hand side) and
one ":bro:type:`string`" operand, but tests whether the pattern
appears anywhere within the given string. For example::
/foo|bar/ in "foobar"
@ -203,27 +231,12 @@ The Bro scripting language supports the following built-in types.
is false since "oob" does not appear at the start of "foobar". The
``!in`` operator would yield the negation of ``in``.
.. bro:type:: enum
A type allowing the specification of a set of related values that
have no further structure. An example declaration:
.. code:: bro
type color: enum { Red, White, Blue, };
The last comma after ``Blue`` is optional.
The only operations allowed on enumerations are equality comparisons
(``==``, ``!=``) and assignment (``=``).
Enumerations do not have associated values or ordering.
.. bro:type:: port
A type representing transport-level port numbers. Besides TCP and
A type representing transport-level port numbers (besides TCP and
UDP ports, there is a concept of an ICMP "port" where the source
port is the ICMP message type and the destination port the ICMP
message code. A ``port`` constant is written as an unsigned integer
message code). A ``port`` constant is written as an unsigned integer
followed by one of ``/tcp``, ``/udp``, ``/icmp``, or ``/unknown``.
Ports support the comparison operators (``==``, ``!=``, ``<``, ``<=``,
@ -255,14 +268,6 @@ The Bro scripting language supports the following built-in types.
address) are treated internally as IPv4 addresses (for example,
``[::ffff:192.168.1.100]`` is equal to ``192.168.1.100``).
Hostname constants can also be used, but since a hostname can
correspond to multiple IP addresses, the type of such a variable is a
:bro:type:`set` of :bro:type:`addr` elements. For example:
.. code:: bro
local a = www.google.com;
Addresses can be compared for equality (``==``, ``!=``),
and also for ordering (``<``, ``<=``, ``>``, ``>=``). The absolute value
of an address gives the size in bits (32 for IPv4, and 128 for IPv6).
@ -285,9 +290,17 @@ The Bro scripting language supports the following built-in types.
if ( a in s )
print "true";
Note that you can check if a given ``addr`` is IPv4 or IPv6 using
You can check if a given ``addr`` is IPv4 or IPv6 using
the :bro:id:`is_v4_addr` and :bro:id:`is_v6_addr` built-in functions.
Note that hostname constants can also be used, but since a hostname can
correspond to multiple IP addresses, the type of such a variable is
"set[addr]". For example:
.. code:: bro
local a = www.google.com;
.. bro:type:: subnet
A type representing a block of IP addresses in CIDR notation. A
@ -296,13 +309,24 @@ The Bro scripting language supports the following built-in types.
number. For example, ``192.168.0.0/16`` or ``[fe80::]/64``.
Subnets can be compared for equality (``==``, ``!=``). An
:bro:type:`addr` can be checked for inclusion in a subnet using
the "in" or "!in" operators.
"addr" can be checked for inclusion in a subnet using
the ``in`` or ``!in`` operators.
.. bro:type:: any
.. bro:type:: enum
Used to bypass strong typing. For example, a function can take an
argument of type ``any`` when it may be of different types.
A type allowing the specification of a set of related values that
have no further structure. An example declaration:
.. code:: bro
type color: enum { Red, White, Blue, };
The last comma after ``Blue`` is optional. Both the type name ``color``
and the individual values (``Red``, etc.) have global scope.
Enumerations do not have associated values or ordering.
The only operations allowed on enumerations are equality comparisons
(``==``, ``!=``) and assignment (``=``).
.. bro:type:: table
@ -316,24 +340,25 @@ The Bro scripting language supports the following built-in types.
table [ type^+ ] of type
where *type^+* is one or more types, separated by commas. For example:
where *type^+* is one or more types, separated by commas.
For example:
.. code:: bro
global a: table[count] of string;
declares a table indexed by :bro:type:`count` values and yielding
:bro:type:`string` values. The yield type can also be more complex:
declares a table indexed by "count" values and yielding
"string" values. The yield type can also be more complex:
.. code:: bro
global a: table[count] of table[addr, port] of string;
which declares a table indexed by :bro:type:`count` and yielding
another :bro:type:`table` which is indexed by an :bro:type:`addr`
and :bro:type:`port` to yield a :bro:type:`string`.
which declares a table indexed by "count" and yielding
another "table" which is indexed by an "addr"
and "port" to yield a "string".
Initialization of tables occurs by enclosing a set of initializers within
One way to initialize a table is by enclosing a set of initializers within
braces, for example:
.. code:: bro
@ -343,18 +368,17 @@ The Bro scripting language supports the following built-in types.
[5] = "five",
};
A table constructor (equivalent to above example) can also be used
to create a table:
A table constructor can also be used to create a table:
.. code:: bro
global t2: table[count] of string = table(
[11] = "eleven",
[5] = "five"
global t2 = table(
[192.168.0.2, 22/tcp] = "ssh",
[192.168.0.3, 80/tcp] = "http"
);
Table constructors can also be explicitly named by a type, which is
useful for when a more complex index type could otherwise be
useful when a more complex index type could otherwise be
ambiguous:
.. code:: bro
@ -381,17 +405,7 @@ The Bro scripting language supports the following built-in types.
if ( 13 in t )
...
Iterate over tables with a ``for`` loop:
.. code:: bro
local t: table[count] of string;
for ( n in t )
...
local services: table[addr, port] of string;
for ( [a, p] in services )
if ( [192.168.0.2, 22/tcp] in t2 )
...
Add or overwrite individual table elements by assignment:
@ -400,7 +414,7 @@ The Bro scripting language supports the following built-in types.
t[13] = "thirteen";
Remove individual table elements with ``delete``:
Remove individual table elements with :bro:keyword:`delete`:
.. code:: bro
@ -416,6 +430,9 @@ The Bro scripting language supports the following built-in types.
|t|
See the :bro:keyword:`for` statement for info on how to iterate over
the elements in a table.
.. bro:type:: set
A set is like a :bro:type:`table`, but it is a collection of indices
@ -426,25 +443,22 @@ The Bro scripting language supports the following built-in types.
where *type^+* is one or more types separated by commas.
Sets are initialized by listing elements enclosed by curly braces:
Sets can be initialized by listing elements enclosed by curly braces:
.. code:: bro
global s: set[port] = { 21/tcp, 23/tcp, 80/tcp, 443/tcp };
global s2: set[port, string] = { [21/tcp, "ftp"], [23/tcp, "telnet"] };
The types are explicitly shown in the example above, but they could
have been left to type inference.
A set constructor (equivalent to above example) can also be used to
create a set:
.. code:: bro
global s3: set[port] = set(21/tcp, 23/tcp, 80/tcp, 443/tcp);
global s3 = set(21/tcp, 23/tcp, 80/tcp, 443/tcp);
Set constructors can also be explicitly named by a type, which is
useful for when a more complex index type could otherwise be
useful when a more complex index type could otherwise be
ambiguous:
.. code:: bro
@ -465,18 +479,10 @@ The Bro scripting language supports the following built-in types.
if ( 21/tcp in s )
...
if ( 21/tcp !in s )
if ( [21/tcp, "ftp"] !in s2 )
...
Iterate over a set with a ``for`` loop:
.. code:: bro
local s: set[port];
for ( p in s )
...
Elements are added with ``add``:
Elements are added with :bro:keyword:`add`:
.. code:: bro
@ -485,7 +491,7 @@ The Bro scripting language supports the following built-in types.
Nothing happens if the element with value ``22/tcp`` was already present in
the set.
And removed with ``delete``:
And removed with :bro:keyword:`delete`:
.. code:: bro
@ -501,6 +507,9 @@ The Bro scripting language supports the following built-in types.
|s|
See the :bro:keyword:`for` statement for info on how to iterate over
the elements in a set.
.. bro:type:: vector
A vector is like a :bro:type:`table`, except it's always indexed by a
@ -515,7 +524,7 @@ The Bro scripting language supports the following built-in types.
.. code:: bro
global v: vector of string = vector("one", "two", "three");
local v = vector("one", "two", "three");
Vector constructors can also be explicitly named by a type, which
is useful for when a more complex yield type could otherwise be
@ -539,14 +548,6 @@ The Bro scripting language supports the following built-in types.
print v[2];
Iterate over a vector with a ``for`` loop:
.. code:: bro
local v: vector of string;
for ( n in v )
...
An element can be added to a vector by assigning the value (a value
that already exists at that index will be overwritten):
@ -577,11 +578,17 @@ The Bro scripting language supports the following built-in types.
The resulting vector of bool is the logical "and" (or logical "or") of
each element of the operand vectors.
See the :bro:keyword:`for` statement for info on how to iterate over
the elements in a vector.
.. bro:type:: record
A ``record`` is a collection of values. Each value has a field name
A "record" is a collection of values. Each value has a field name
and a type. Values do not need to have the same type and the types
have no restrictions. An example record type definition:
have no restrictions. Field names must follow the same syntax as
regular variable names (except that field names are allowed to be the
same as local or global variables). An example record type
definition:
.. code:: bro
@ -590,85 +597,44 @@ The Bro scripting language supports the following built-in types.
s: string &optional;
};
Access to a record field uses the dollar sign (``$``) operator:
.. code:: bro
global r: MyRecordType;
r$c = 13;
Record assignment can be done field by field or as a whole like:
.. code:: bro
r = [$c = 13, $s = "thirteen"];
Records can be initialized or assigned as a whole in three different ways.
When assigning a whole record value, all fields that are not
:bro:attr:`&optional` or have a :bro:attr:`&default` attribute must
be specified.
To test for existence of a field that is :bro:attr:`&optional`, use the
``?$`` operator:
be specified. First, there's a constructor syntax:
.. code:: bro
if ( r?$s )
...
Records can also be created using a constructor syntax:
.. code:: bro
global r2: MyRecordType = record($c = 7);
local r: MyRecordType = record($c = 7);
And the constructor can be explicitly named by type, too, which
is arguably more readable code:
is arguably more readable:
.. code:: bro
global r3 = MyRecordType($c = 42);
local r = MyRecordType($c = 42);
.. bro:type:: opaque
A data type whose actual representation/implementation is
intentionally hidden, but whose values may be passed to certain
functions that can actually access the internal/hidden resources.
Opaque types are differentiated from each other by qualifying them
like ``opaque of md5`` or ``opaque of sha1``. Any valid identifier
can be used as the type qualifier.
An example use of this type is the set of built-in functions which
perform hashing:
And the third way is like this:
.. code:: bro
local handle: opaque of md5 = md5_hash_init();
md5_hash_update(handle, "test");
md5_hash_update(handle, "testing");
print md5_hash_finish(handle);
local r: MyRecordType = [$c = 13, $s = "thirteen"];
Here the opaque type is used to provide a handle to a particular
resource which is calculating an MD5 checksum incrementally over
time, but the details of that resource aren't relevant, it's only
necessary to have a handle as a way of identifying it and
distinguishing it from other such resources.
.. bro:type:: file
Bro supports writing to files, but not reading from them. Files
can be opened using either the :bro:id:`open` or :bro:id:`open_for_append`
built-in functions, and closed using the :bro:id:`close` built-in
function. For example, declare, open, and write to a file
and finally close it like:
Access to a record field uses the dollar sign (``$``) operator, and
record fields can be assigned with this:
.. code:: bro
global f: file = open("myfile");
print f, "hello, world";
close(f);
local r: MyRecordType;
r$c = 13;
Writing to files like this for logging usually isn't recommended, for better
logging support see :doc:`/frameworks/logging`.
To test if a field that is :bro:attr:`&optional` has been assigned a
value, use the ``?$`` operator (it returns a :bro:type:`bool` value of
``T`` if the field has been assigned a value, or ``F`` if not):
.. code:: bro
if ( r ?$ s )
...
.. bro:type:: function
@ -700,6 +666,16 @@ The Bro scripting language supports the following built-in types.
type, but when it is, the return type and argument list (including the
name of each argument) must match exactly.
Here is an example function that takes no parameters and does not
return a value:
.. code:: bro
function my_func()
{
print "my_func";
}
Function types don't need to have a name and can be assigned anonymously:
.. code:: bro
@ -742,9 +718,20 @@ The Bro scripting language supports the following built-in types.
Event handlers are nearly identical in both syntax and semantics to
a :bro:type:`function`, with the two differences being that event
handlers have no return type since they never return a value, and
you cannot call an event handler. Instead of directly calling an
event handler from a script, event handler bodies are executed when
they are invoked by one of three different methods:
you cannot call an event handler.
Example:
.. code:: bro
event my_event(r: bool, s: string)
{
print "my_event", r, s;
}
Instead of directly calling an event handler from a script, event
handler bodies are executed when they are invoked by one of three
different methods:
- From the event engine
@ -765,7 +752,7 @@ The Bro scripting language supports the following built-in types.
This assumes that ``password_exposed`` was previously declared
as an event handler type with compatible arguments.
- Via the ``schedule`` expression in a script
- Via the :bro:keyword:`schedule` expression in a script
This delays the invocation of event handlers until some time in
the future. For example:
@ -789,8 +776,8 @@ The Bro scripting language supports the following built-in types.
immediate and they do not get scheduled through an event queue.
Also, a unique feature of a hook is that a given hook handler body
can short-circuit the execution of remaining hook handlers simply by
exiting from the body as a result of a ``break`` statement (as
opposed to a ``return`` or just reaching the end of the body).
exiting from the body as a result of a :bro:keyword:`break` statement (as
opposed to a :bro:keyword:`return` or just reaching the end of the body).
A hook type is declared like::
@ -859,142 +846,60 @@ The Bro scripting language supports the following built-in types.
executed due to one handler body exiting as a result of a ``break``
statement.
Attributes
----------
.. bro:type:: file
Attributes occur at the end of type/event declarations and change their
behavior. The syntax is ``&key`` or ``&key=val``, e.g., ``type T:
set[count] &read_expire=5min`` or ``event foo() &priority=-3``. The Bro
scripting language supports the following built-in attributes.
Bro supports writing to files, but not reading from them (to read from
files see the :doc:`/frameworks/input`). Files
can be opened using either the :bro:id:`open` or :bro:id:`open_for_append`
built-in functions, and closed using the :bro:id:`close` built-in
function. For example, declare, open, and write to a file and finally
close it like:
.. bro:attr:: &optional
.. code:: bro
Allows a record field to be missing. For example the type ``record {
a: addr; b: port &optional; }`` could be instantiated both as
singleton ``[$a=127.0.0.1]`` or pair ``[$a=127.0.0.1, $b=80/tcp]``.
local f = open("myfile");
print f, "hello, world";
close(f);
.. bro:attr:: &default
Writing to files like this for logging usually isn't recommended, for better
logging support see :doc:`/frameworks/logging`.
Uses a default value for a record field, a function/hook/event
parameter, or container elements. For example, ``table[int] of
string &default="foo"`` would create a table that returns the
:bro:type:`string` ``"foo"`` for any non-existing index.
.. bro:type:: opaque
.. bro:attr:: &redef
A data type whose actual representation/implementation is
intentionally hidden, but whose values may be passed to certain
built-in functions that can actually access the internal/hidden resources.
Opaque types are differentiated from each other by qualifying them
like "opaque of md5" or "opaque of sha1".
Allows for redefinition of initial object values. This is typically
used with constants, for example, ``const clever = T &redef;`` would
allow the constant to be redefined at some later point during script
execution.
An example use of this type is the set of built-in functions which
perform hashing:
.. bro:attr:: &rotate_interval
.. code:: bro
Rotates a file after a specified interval.
local handle = md5_hash_init();
md5_hash_update(handle, "test");
md5_hash_update(handle, "testing");
print md5_hash_finish(handle);
.. bro:attr:: &rotate_size
Here the opaque type is used to provide a handle to a particular
resource which is calculating an MD5 hash incrementally over
time, but the details of that resource aren't relevant, it's only
necessary to have a handle as a way of identifying it and
distinguishing it from other such resources.
Rotates a file after it has reached a given size in bytes.
.. bro:type:: any
.. bro:attr:: &add_func
Used to bypass strong typing. For example, a function can take an
argument of type ``any`` when it may be of different types.
The only operation allowed on a variable of type ``any`` is assignment.
Can be applied to an identifier with &redef to specify a function to
be called any time a "redef <id> += ..." declaration is parsed. The
function takes two arguments of the same type as the identifier, the first
being the old value of the variable and the second being the new
value given after the "+=" operator in the "redef" declaration. The
return value of the function will be the actual new value of the
variable after the "redef" declaration is parsed.
Note that users aren't expected to use this type. It's provided mainly
for use by some built-in functions and scripts included with Bro.
.. bro:attr:: &delete_func
.. bro:type:: void
Same as &add_func, except for "redef" declarations that use the "-="
operator.
An internal Bro type (i.e., "void" is not a reserved keyword in the Bro
scripting language) representing the absence of a return type for a
function.
.. bro:attr:: &expire_func
Called right before a container element expires. The function's
first parameter is of the same type of the container and the second
parameter the same type of the container's index. The return
value is an :bro:type:`interval` indicating the amount of additional
time to wait before expiring the container element at the given
index (which will trigger another execution of this function).
.. bro:attr:: &read_expire
Specifies a read expiration timeout for container elements. That is,
the element expires after the given amount of time since the last
time it has been read. Note that a write also counts as a read.
.. bro:attr:: &write_expire
Specifies a write expiration timeout for container elements. That
is, the element expires after the given amount of time since the
last time it has been written.
.. bro:attr:: &create_expire
Specifies a creation expiration timeout for container elements. That
is, the element expires after the given amount of time since it has
been inserted into the container, regardless of any reads or writes.
.. bro:attr:: &persistent
Makes a variable persistent, i.e., its value is written to disk (per
default at shutdown time).
.. bro:attr:: &synchronized
Synchronizes variable accesses across nodes. The value of a
``&synchronized`` variable is automatically propagated to all peers
when it changes.
.. bro:attr:: &encrypt
Encrypts files right before writing them to disk.
.. TODO: needs to be documented in more detail.
.. bro:attr:: &raw_output
Opens a file in raw mode, i.e., non-ASCII characters are not
escaped.
.. bro:attr:: &mergeable
Prefers set union to assignment for synchronized state. This
attribute is used in conjunction with :bro:attr:`&synchronized`
container types: when the same container is updated at two peers
with different value, the propagation of the state causes a race
condition, where the last update succeeds. This can cause
inconsistencies and can be avoided by unifying the two sets, rather
than merely overwriting the old value.
.. bro:attr:: &priority
Specifies the execution priority (as a signed integer) of a hook or
event handler. Higher values are executed before lower ones. The
default value is 0.
.. bro:attr:: &group
Groups event handlers such that those in the same group can be
jointly activated or deactivated.
.. bro:attr:: &log
Writes a record field to the associated log stream.
.. bro:attr:: &error_handler
Internally set on the events that are associated with the reporter
framework: :bro:id:`reporter_info`, :bro:id:`reporter_warning`, and
:bro:id:`reporter_error`. It prevents any handlers of those events
from being able to generate reporter messages that go through any of
those events (i.e., it prevents an infinite event recursion). Instead,
such nested reporter messages are output to stderr.
.. bro:attr:: &type_column
Used by the input framework. It can be used on columns of type
:bro:type:`port` and specifies the name of an additional column in
the input file which specifies the protocol of the port (tcp/udp/icmp).