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System/Kernel/Gall/Reference/Scry Reference

Scry Reference

Gall's scry interface is mainly used to scry into the individual agents it's running. The vane itself does have its own interface, however. Both agent scries and vane scries are documented below.

Note that for all agent scries and most vane scries, q.beak, where there'd usually be a desk, will be the agent name instead, like:

.^(some-type %gx /=agent-name-here=/some/path/noun)

Important: Vane scries are differentiated from agent scries by an extra empty (%$) element at the beginning of the spur (the path after the beak), like: /=agent-name/$ or /=agent-name=//some/more/fields. Without that empty element, Gall will try route the scry to an agent instead.

Agent scries

In order to hit the +on-peek arm of a Gall agent, you need to:

  1. Put the agent in q.beak of the scry path (where the desk usually goes), like /=some-agent=.
  2. Make sure the beginning of the spur is not an empty %$ element, as that will route the scry to the vane endpoints instead. An agent scry must be /=some-agent=/some/path not /=some-agent=//some/path.

Any care can be used (dependent on what the agent accepts, of course). The most common is %x.

Note that %x cares alone must include an extra mark field at the end of the spur. This mark field lets Gall perform any necessary mark conversions before returning your data. For plain unmarked data, you can just use the %noun mark. As an example, if an agent specifies an endpoint /x/some/path and just returns ordinary data, you'd do .^(some-type %gx /=some-agent=/some/path/noun). If the endpoint returns a %json mark or whatever (and that's what you want), you'd put that at the end instead.

Vane scries

Gall itself provides the special vane-level endpoints listed below. They are organized by the care. In order to hit the vane-level endpoints, the beginning of the the spur (e.g. the path after the beak) must be a %$ empty element. For example:

.^(desk %gd /=acme=/$)
.^((set [=dude:gall live=?]) %ge /=base=/$)
.^((list path) %gt /=acme=//foo)

Note you can use $ to make the last element empty since it won't allow a trailing /. Note how in the third example, the empty element is at the beginning of the spur and after the beak. If you fail to include this empty element, Gall will try route the scry to an agent for handling instead.

%d: get desk of app

A scry with a %d care and an agent in q.beak will give you the desk that agent is on.

Produces

A desk

Example

> .^(desk %gd /=acme=/$)
%base

%e: running apps

A scry with an %e care will give you the agents on the desk given in q.beak.

Produces

A (set [=dude live=?]), where live is true if running and false if not.

Examples

> .^((set [=dude:gall live=?]) %ge /=base=/$)
{ [dude=%acme live=%.y]
  [dude=%hood live=%.y]
  [dude=%lens live=%.y]
  [dude=%dbug live=%.y]
  [dude=%azimuth live=%.y]
  [dude=%ping live=%.y]
  [dude=%dojo live=%.y]
  [dude=%eth-watcher live=%.y]
  [dude=%spider live=%.y]
  [dude=%herm live=%.y]
}

%f: nonces of apps

A scry with a care of %f and anything in q.beak will produce the subscription nonces of all apps. You are unlikely to use this, it's mostly for kernel debugging.

Produces

A (map dude @) where the @ is the nonce.

Examples

> .^((map dude:gall @) %gf /=//=/$)
[ n=[p=%treaty q=2]
    l
  [ n=[p=%metadata-hook q=1]
    l={[p=%contacts q=1] [p=%notify q=2] [p=%groups q=1] [p=%dm-hook q=1] [p=%spider q=1]}
      r
    { [p=%docket q=9]
      [p=%bait q=1]
      [p=%hood q=15]
      [p=%hark-graph-hook q=2]
      [p=%s3-store q=1]
      [p=%hark-system-hook q=1]
......(truncated for brevity)......

%n: get nonce of subscription

A scry with a care of %n, an agent in q.beak and a path of //[ship]/[agent]/[wire] will produce the nonce for that subscription. You are unlikely to use this, it's mostly for kernel debugging.

Produces

A @.

%t: remote scry subpaths

A scry with a %t care, an agent in q.beak and a path of //some/path will give you the list of remote scry subpaths bound under the given path.

See the remote scry guide for more details.

Produces

A (list path)

Examples

> .^((list path) %gt /=acme=//foo)
~

%u: check if installed

A scry with a %u care will check whether the given agent is installed and running.

Produces

A ?

Examples

> .^(? %gu /=acme=/$)
%.y
> .^(? %gu /=doesnt-exist=/$)
%.n

%w: latest revision of path

A scry with a %w care and an agent in q.beak will get the latest revision number of the bound remote scry path given in the spur.

See the remote scry guide for more details.

Produces

A cass:clay, specifically the %ud kind.

%x: remote scry file

A scry with a %x care and an agent in q.beak will get the value bound at the remote scry path given in the spur. The revision of the file must be given in the beak portion of the scry path. The general format is therefore:

[%gx /[ship]/[agent]/[file revision]//[file path]

See the remote scry guide for more details.

Produces

The type returned is the raw noun from the page. If the file has been tombstoned or does not exist, the scry will fail.

%z: hash of value at path

A scry with a %z care and an agent in q.beak will get the hash identifier of the value bound at the remote scry path given in the spur.

See the remote scry guide for more details.

Produces

A @uvI.