title: TiddlerFilters
tags: docs concepts

TiddlyWiki has a special syntax for expressing filters. They can be used to select tiddlers for an operation, or to filter a set of tiddlers to add or remove members.

The mechanism is easiest to understand by first presenting some example filter strings:

* `HelloThere` - the single tiddler titled `HelloThere` (if it exists)
* `[[A Title With Several Words]]` - the single tiddler titled `A Title With Several Words` (if it exists)
* `[title[MyTiddler]]` - the single tiddler titled `MyTiddler` (if it exists)
* `HelloThere Introduction` - The tiddlers titled `HelloThere` and `Introduction` (if they exist)
* `[tag[important]]` - any tiddlers with the tag `important`
* `[!tag[important]]` - any tiddlers not with the tag `important`
* `[tag[important]sort[title]]` - any tiddlers with the tag `important` sorted by title
* `[tag[important]!sort[title]]` - any tiddlers with the tag `important` reverse sorted by title
* `[[one][two][three]tag[tom]]` - any of the tiddlers called `one`, `two` or `three` that exist and are tagged with tom`
* `[[one][two][three]] [tag[tom]]` - any of the tiddlers called `one`, `two` or `three` that exist, along with all of the source tiddlers that are tagged with `tom`
* `[tag[tom]] [tag[harry]] -[[one][two][three]]` - all tiddlers tagged either `tom` or `harry`, but excluding `one`, two` and `three`
* `[[MyTiddler]tags[]]` - all tiddlers being used as tags on the tiddler `MyTiddler`
* `[[MyTiddler]tagging[]]` - all tiddlers being tagged with `MyTiddler`

! Explanation

A filter string consists of one or more filter operations, each comprising one or more filter operators with associated operands.

The operators look like `[operator[operand]]`, where `operator` is one of:

* ''title'': selects the tiddler with the title given in the operand
* ''is'': tests whether a tiddler is a member of the system defined set named in the operand (see below)
* ''has'': tests whether a tiddler has a specified field
* ''sort'': sorts the tiddlers by a given field
* ''sort-case-sensitive'': sorts the tiddlers by a given field with case sensitivity (ie, "a" and "A" are sorted differently)
* ''prefix'': tests whether a tiddlers title starts with a particular prefix
* ''limit'': limits the number of subresults
* ''tag'': tests whether a given tag is (`[tag[mytag]]`) or is not (`[!tag[mytag]]`) present on the tiddler
* ''{field}'': tests whether a tiddler field has a specified value (`[modifier[Jeremy]]`) or not (`[!modifier[Jeremy]]`)
* ''tags'': selects the tags on the currently selected tiddlers
* ''tagging'': selects the tiddlers tagged with the currently selected tiddlers

An operator can be negated with by preceding it with `!`, for example `[!tag[Tommy]]` selects the tiddlers that are not tagged with `Tommy`.

The operator defaults to `title` if omitted, so `[[HelloThere]]` is equivalent to `[title[HelloThere]]`. If there are no spaces in the title, then the double square brackets can also be omitted: `HelloThere`.

The operands available with the `is` operator are:

* ''shadow'': selects all shadow tiddlers
* ''current'': selects the current ContextTiddler

Operators are combined into logically ANDed expressions by bashing them together and merging the square brackets:

{{{
[tag[one]] [tag[two]] ---> [tag[one]tag[two]]
}}}

Operations can be preceded with `-` to negate their action, removing the selected tiddlers from the results. For example, `[tag[Tommy]] -HelloThere -[[Another One]]` selects all tiddlers tagged with `Tommy` except those titled `HelloThere` or `Another One`.

Operations can be preceded with `+` in order to make them apply to all of the current results, rather than the original source. For example, `[tag[Jeremy]] [tag[Tommy]] +[sort[title]]` selects the tiddlers tagged `Tommy` or `Jeremy`, and sorts them by the `title` field.

Filters are processed with the following elements:

* a string of filter operations, each made up of one or more filter operators
* the incoming source tiddlers
* the overall result stack
* the subresult stack of the tiddlers selected by the current operation