Actions

Here is the list of actions. Arguments and pipelines are evaluations of data, defined in detail in the corresponding sections that follow.

{{ }}

Empty action is discarded. It may be useful to trim the preceding or following whitespace, as in {{- -}} .

{{/* a comment */}}

Comments are discarded. They may span multiple lines of text. Comments do not nest and must start immediately after the opening delimiter (with optional dash and whitespace in between). A comment may be followed by any action described below.

Comments may be used to control trailing and leading whitespace as well:

{{- a comment trimming the surrounding whitespace -}}
    

{{pipeline}}

Pipeline is evaluated, and the default textual representation of its value is copied to the output.

{{if pipeline}} T1 {{end}}

If the value of the pipeline is empty, no output is generated; otherwise, T1 is executed. The empty values are null, false, numeric 0, empty string (""), array ([]), or object ({}). Dot is unaffected.

{{if pipeline}} T1 {{else}} T0 {{end}}

If the value of the pipeline is empty, T0 is executed; otherwise, T1 is executed. Dot is unaffected.

{{if pipeline}} T1 {{else if pipeline}} T2 {{else}} T0 {{end}}

A shortcut to simplify writing the if-else chains. Equivalent to (newlines added for readability):

{{if pipeline }}
  T1
{{else -}}
 {{if pipeline }}
   T2
 {{else}}
   T0
 {{end}}
{{end}}
    

{{range pipeline}} T1 {{end}}

The value of pipeline must be an object or array. If it is of length zero, nothing is output. Otherwise, dot is set to the successive elements of the array or object and T1 is executed. For objects, the elements will be visited in sorted key order.

{{range pipeline}} T1 {{else}} T0 {{end}}

Same as above, except that if the value of the pipeline is of length zero, T0 is executed with dot unaffected.

Within the {{range}} action, the following two keywords may appear:

{{break}}

The innermost {{range pipeline}} loop is ended early, stopping the current iteration and bypassing all remaining iterations.

{{continue}}

The current iteration of the innermost {{range pipeline}} loop is stopped, and the loop starts the next iteration.

{{define "name"}} text {{end}}

The text is collected and stored for the further use as template with the given name. It can be invoked using the {{template}} action (see below).

{{template "name"}}

The template with the specified name (see the {{define}} above) is executed with dot set to null.

{{template "name" value}}

The template with the specified name (see the {{define}} above) is executed with dot set to value.

{{block "name" pipeline}} T1 {{end}}

A block is shorthand for defining a template

{{define "name"}} T1 {{end}}
    

and then executing it in place

{{template "name" pipeline}}
    

{{with pipeline}} T1 {{end}}

If the value of the pipeline is empty, no output is generated; otherwise, dot is set to the value of the pipeline and T1 is executed.

{{with pipeline}} T1 {{else}} T0 {{end}}

Same as above, but if the value of the pipeline is empty, T0 is executed with dot unchanged.

Arguments

An argument is a simple value, i.e. any of the following:

Numeric value (integer or floating point)

Boolean value: true or false.

Quoted string.

A dot (.)

This represents the cursor value.

Attribute: .Attr

This is the value of the attribute Attr in the current value (dot).

Attribute references can be nested, as in .Attr.Xattr.Yattr.

A variable reference: $var.

Here, var is the name of the variable defined in the range action. See the subsection Variables, below.

Function call in parentheses, for grouping.

Pipelines

A pipeline is a series of one or more commands delimited by pipe sign (|). Each command is either an argument or a function call, in form:

func arg1 arg2...

where func is the name of one of the built-in functions discussed below.

Pipelines are executed from left to right, with the result of the previous command implicitly added to the list of arguments of each subsequent command. For example, the pipeline

.attr | eq $x

is equivalent to

eq $x .attr

i.e. it calls the built-in function eq with two arguments: the value of the variable x and attribute attr of the cursor value.

The following built-in functions are defined:

and A1 A2

Evaluates to true if pipelines A1 and A2 both evaluate to true. Notice, that there is no boolean shortcut evaluation: both pipelines are evaluated prior to calling and.

or A1 A2

Evaluates to true if at least one of the pipelines A1 and A2 evaluates to true. Notice, that there is no boolean shortcut evaluation: both pipelines are evaluated prior to calling or.

index A1 A2...

Returns the result of indexing its first argument by the following arguments. Thus, if . is an array, then:

index . 5
    

evaluates to its fifth element (.[5]).

len A1

Returns the integer length of its argument.

not A1

Returns true if its argument evaluates to false.

eq A1 A2

Returns true if both its arguments are equal. This applies only if both A1 and A2 are numeric or if they both are strings.

ne A1 A2

Returns true if its arguments (both must be numeric or strings) are not equal.

lt A1 A2

Returns true if A1 is numerically less than A2.

le A1 A2

Returns true if A1 is numerically less than or equal to A2.

gt A1 A2

Returns true if A1 is numerically greater than A2.

ge A1 A2

Returns true if A1 is numerically greater than or equal to A2.

even A1

Returns true if A1, which must evaluate to an integer value, is divisible by 2.

printf FMT A1...

Implements the printf(3) function. FMT must evaluate to a string. Rest of arguments is interpreted according to the conversion specifications in FMT. The result is a formatted string.

In addition to the standard conversion specifications described in printf(3), the "%v" specifier is implemented: it formats its argument in the best way, depending on its actual type.

typeof A1

Evaluates to the type of its argument, one of: null, bool, number, integer, string, array, object.

exists A1 A2

A1 must evaluate to an object and A2 to string. The function evaluates to true if the attribute A2 is present in A1.

add A1 A2...

Returns the sum of its arguments.

sub A1 A2

Returns the difference A1 - A2.

mul A1 A2

Multiplies A1 by A2.

div A1 A2

Divides A1 by A2.

Variables

Variables (referred to as $name) can be defined in range and with actions. For range, the syntax is:

{{range $index, $element = pipeline}} T1 {{end}}

where index and element are arbitrary variable names. When executing this action, during each iteration $index and $element are set to the index (attribute name) and value of each successive element. Dot remains unaffected.

For with, the syntax is:

{{with $var = pipeline}} T1 {{end}}

Pipeline is evaluated, its result is assigned to $var and the T1 block is executed with dot unchanged.

A variable's scope extends to the end action of the control structure (with or range) in which it is declared. This includes any nested statements that may appear in between.

Full listing

A full listing contains the following attributes:

listeners

An array of listener objects. See below for a description.

services

An array of service objects, representing services defined in the global scope of the pound configuration file.

pid

PID of the running pound daemon.

version

Pound version number (string).

workers

Workers statistics. This is a JSON object with the following attributes:

queue_len

Number of incoming HTTP requests in the queue (integer).

timestamp

Current time on the server, formatted as ISO 8601 date-time with microsecond precision, e.g.: "2023-01-05T22:43:18.071559".

Listener

A listener object represents a single HTTP or HTTPS listener in pound configuration. It has the following attributes:

address

String. Address of this listener. A string formatted as "IP:PORT" for IPv4 and IPv6 addresses or containing socket file name, for UNIX sockets.

protocol

String. Protocol used: either http or https.

services

Array of service objects representing services defined in this listener. See below for the definition of a service object.

enabled

Boolean. Whether this listener is enabled or not.

nohttps11

Integer. Value of the NoHTTPS11 configuration statement for this listener. One of: 0, 1, 2.

Service

A service object describes a single service.

name

String. Symbolic name of this service.

enabled

Boolean. Whether this service is enabled or not.

session_type

String. Name of the session handling algorithm for this service. One of: IP, BASIC, URL, PARM, COOKIE, HEADER.

sessions

List of active sessions in this service. Each session is represented as object with the following attributes:

backends

List of backends defined for this service.

emergency

Emergency backend object, or null if no such backend is defined.

Backend

The following attributes are always present in each backend object:

alive

Boolean. Whether or not this backend is alive.

conn_to

Integer. Connection timeout for this backend (seconds).

enabled

Boolean. Whether or not this backend is enabled.

io_to

Integer. I/O timeout for this backend (seconds).

priority

Integer in range 0-9. Priority value assigned to this backend.

protocol

String. Protocol used by this backend: either http or https.

type

String. Backend type. One of: acme, backend, control, redirect.

ws_to

Integer Websocket timeout (seconds).

Depending on the backend type, the following attributes may be present:

acme

backend

redirect

If backend statistics is enabled (see BackendStats in pound(8)), the stats object will be present, with the following attributes:

request_count

Total number of requests processed by this backend.

request_time_avg

Average time per request, in nanoseconds.

request_time_stddev

Standard deviation of the above.