---
pageid: file-query
title: File Queries
layout: docs
section: Queries
permalink: docs/file-query.html
redirect_from: docs/file-query/
---

Watchman file queries consist of 1 or more *generators* that feed files through
the *expression evaluator*.

### Generators

Generators are analogous to the list of *paths* that you specify when using the
`find(1)` utility, but are implemented in watchman with a bit of a twist
because watchman doesn't need to crawl the filesystem in realtime and instead
maintains a couple of indexes over the tree.

A query may specify any number of generators; each generator will emit its list
of files and this may mean that you see the same file output more than once if
you specified the use of multiple generators that all produce the same file.

Watchman provides 5 generators:

 * **since**: produces a list of files that were modified since a specific
   clockspec.
 * **suffix**: produces a list of files that have a particular suffix.
 * **glob**: efficiently pattern match a list of files based on their names.
 * **path**: produces a list of files based on their path and depth.
 * **all**: produces a list of all known files


### De-duplicating results

*Since 4.7.*

If your query uses multiple generators, or configures the `path` generator with
paths that yield multiple results, the default behavior (for backwards
compatibility reasons) is to emit those duplicate results in the query output.

You may ask Watchman to de-duplicate results for you by enabling the
`dedup_results` boolean in your query:

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "path": ["bar", "bar"],
  "dedup_results": true
}]
EOT
~~~

You may test for this feature using an extended version command and requesting
the capability name `dedup_results`.

### Since Generator

The `since` generator produces a list of files that were modified since a
specific [clockspec](../docs/clockspec.html).

The following query will consider the set of files changed since the last
query using the named cursor `mycursor` and then pass them to the expression
evaluator to be filtered to just those that are files:

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "since": "n:mycursor",
  "expression": ["type", "f"]
}]
EOT
~~~

If the `since` parameter value is blank, was produced by a different watchman
process (in other words, the watchman process was restarted between the time
that the value was obtained and the time the query was issued) or is a named
cursor that has not yet been used in a query, the `since` generator will
consider the state to be a *fresh instance* and its behavior is modified:

A *fresh instance* result set will only include files that currently exist
and will generate file nodes that are always considered to be `new`.

If the query was configured with the `empty_on_fresh_instance` property set to
`true` then the result set will be empty and the `is_fresh_instance` property
will be set to `true` in the result object.

The since generator also knows how to talk to source control;
[you can read more about that here](/watchman/docs/scm-query.html).

The `since` generator does not consider the targets of symlinks. In particular,
the `since` generator may *not* produce a symlink in the following cases:

* The symlink's target was a file, and the file is since modified.
* The symlink's target was a file, and the file is since deleted or replaced
  with a different file.
* An ancestor of the symlink's target was created or deleted or modified.
* The symlink's target was a directory, and a file is since added or removed
  from that directory.

### Suffix Generator

The `suffix` generator produces a list of files that have a particular suffix
or set of suffixes.  The value can be either a string or an array of strings.

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "suffix": "js"
}]
EOT
~~~

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "suffix": ["js", "css"]
}]
EOT
~~~

If the `suffix` generator is given an empty array, it produces no files.

The `suffix` generator can produce symlinks.

The `suffix` generator does not follow symlinks. For example, a symlink to
`/etc` will not cause a `"suffix": "conf"` query to search within `/etc` and
produce `/etc/resolv.conf`.

### Glob Generator

*Since 4.7.*

The `glob` generator produces a list of files by matching against your
input list of patterns.  It does this by building a tree from the glob
expression(s) and walking both the expression and the in-memory filesystem
tree concurrently.

This query will yield a list of all of the C source and header files found
directly in the `src` dir:

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "glob": ["src/*.c", "src/*.h"],
  "fields": ["name"]
}]
~~~

This query will yield a list of all of the C source and header files found
in any subdirectories of the root:

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "glob": ["**/*.c", "**/*.h"],
  "fields": ["name"]
}]
~~~

Note that it is more efficient to use the `suffix` generator together with a
`dirname` expression term for such a broadly scoped query as it results in
fewer comparisons.  This example is included as an illustration of recursive
globbing.

The glob generator implicitly enables `dedup_results` mode.

If the `glob` generator is given an empty array, it produces no files.

The `glob` generator can produce symlinks.

The `glob` generator does not follow symlinks. For example, a symlink to `/etc`
will not cause a `"glob": ["**/resolv.conf"]` query to search within `/etc` and
produce `/etc/resolv.conf`.

### Path Generator

The `path` generator produces a list of files based on their path and depth.
Depth controls how far watchman will search down the directory tree for files.

The `path` generator expects an array of path specifiers.  Each path specifier
can be either a string or an object and each will produce a set of files.

If it is a string then it is treated as the value for `path` with `depth` set
to infinite.  If an object, the fields `path` (a string) and `depth` (an
integer) must be supplied.

Paths are relative to the root, so if watchman is watching `/foo/`, path `bar`
refers to `/foo/bar`.

A `depth` value of `0` means only files and directories which are contained in
this path.  A `depth` value of `-1` means no limit on the depth.

The following `path` generators are equivalent:

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "path": ["bar"]
}]
EOT
~~~

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
  "path": [{"path": "bar", "depth": -1}]
}]
EOT
~~~

If the `path` generator is given an empty array, it produces no files.

The `path` generator can produce symlinks.

The `path` generator does not follow symlinks.

### All Generator

The `all` generator produces a list of all file nodes.  It is the default
generator and is used in the case where no other generators were explicitly
specified.

~~~bash
$ watchman -j <<-EOT
["query", "/path/to/root", {
}]
EOT
~~~

The `all` generator can produce symlinks.

The `all` generator does not follow symlinks.

### Expressions

A watchman query expression consists of 0 or more expression terms.  If no
terms are provided then each file evaluated is considered a match (equivalent
to specifying a single `true` expression term).

Otherwise, the expression is evaluated against the file and produces a boolean
result.  If that result is true then the file is considered a match and is
added to the output set.

An expression term is canonically represented as a JSON array whose zeroth
element is a string containing the term name.

~~~json
["termname", arg1, arg2]
~~~

If the term accepts no arguments you may use a short form that consists of just
the term name expressed as a string:

~~~json
"true"
~~~

Expressions that match against file names may match against either the
*basename* or the *wholename* of the file.  The basename is the name of the
file within its containing directory.  The wholename is the name of the file
relative to the watched root.

You can find a list of all possible expression terms in the sidebar on the left
of this page.

### Relative roots

*Since 3.3.*

Watchman supports optionally evaluating queries with respect to a path within a
watched root. This is used with the `relative_root` parameter:

~~~json
["query", "/path/to/watched/root", {
  "relative_root": "project1",
}]
~~~

Setting a relative root results in the following modifications to queries:

* The `path` generator is evaluated with respect to the relative root. In the
  above example, `"path": ["dir"]` will return all files inside
  `/path/to/watched/root/project1/dir`.
* The input expression is evaluated with respect to the relative root. In the
  above example, `"expression": ["match", "dir/*.txt", "wholename"]` will return
  all files inside `/path/to/watched/root/project1/dir/` that match the glob
  `*.txt`.
* Paths inside the relative root are returned with the relative root stripped
  off. For example, a path `project1/dir/file.txt` would be returned as
  `dir/file.txt`.
* Paths outside the relative root are not returned.

Relative roots behave similarly to a separate Watchman watch on the
subdirectory, without any of the system overhead that that imposes. This is
useful for large repositories, where your script or tool is only interested in a
particular directory inside the repository.
