Provided by: nix-bin_2.18.1+dfsg-1ubuntu5_amd64 
Name
nix-env --query - display information about packages
Synopsis
nix-env {--query | -q} names… [--installed | --available | -a] [{--status | -s}] [{--attr-
path | -P}] [--no-name] [{--compare-versions | -c}] [--system] [--drv-path] [--out-path]
[--description] [--meta] [--xml] [--json] [{--prebuilt-only | -b}] [{--attr | -A}
attribute-path]
Description
The query operation displays information about either the store paths that are installed
in the current generation of the active profile (--installed), or the derivations that are
available for installation in the active Nix expression (--available). It only prints
information about derivations whose symbolic name matches one of names.
The derivations are sorted by their name attributes.
Source selection
The following flags specify the set of things on which the query operates.
• --installed
The query operates on the store paths that are installed in the current generation of
the active profile. This is the default.
• --available; -a
The query operates on the derivations that are available in the active Nix expression.
Queries
The following flags specify what information to display about the selected derivations.
Multiple flags may be specified, in which case the information is shown in the order given
here. Note that the name of the derivation is shown unless --no-name is specified.
• --xml
Print the result in an XML representation suitable for automatic processing by other
tools. The root element is called items, which contains a item element for each
available or installed derivation. The fields discussed below are all stored in
attributes of the item elements.
• --json
Print the result in a JSON representation suitable for automatic processing by other
tools.
• --prebuilt-only / -b
Show only derivations for which a substitute is registered, i.e., there is a pre-built
binary available that can be downloaded in lieu of building the derivation. Thus, this
shows all packages that probably can be installed quickly.
• --status; -s
Print the status of the derivation. The status consists of three characters. The first
is I or -, indicating whether the derivation is currently installed in the current
generation of the active profile. This is by definition the case for --installed, but
not for --available. The second is P or -, indicating whether the derivation is present
on the system. This indicates whether installation of an available derivation will
require the derivation to be built. The third is S or -, indicating whether a
substitute is available for the derivation.
• --attr-path; -P
Print the attribute path of the derivation, which can be used to unambiguously select
it using the --attr option available in commands that install derivations like nix-env
--install. This option only works together with --available
• --no-name
Suppress printing of the name attribute of each derivation.
• --compare-versions / -c
Compare installed versions to available versions, or vice versa (if --available is
given). This is useful for quickly seeing whether upgrades for installed packages are
available in a Nix expression. A column is added with the following meaning:
• < version
A newer version of the package is available or installed.
• = version
At most the same version of the package is available or installed.
• > version
Only older versions of the package are available or installed.
• - ?
No version of the package is available or installed.
• --system
Print the system attribute of the derivation.
• --drv-path
Print the path of the store derivation.
• --out-path
Print the output path of the derivation.
• --description
Print a short (one-line) description of the derivation, if available. The description
is taken from the meta.description attribute of the derivation.
• --meta
Print all of the meta-attributes of the derivation. This option is only available with
--xml or --json.
Options
The following options are allowed for all nix-env operations, but may not always have an
effect.
• --file / -f path
Specifies the Nix expression (designated below as the active Nix expression) used by
the --install, --upgrade, and --query --available operations to obtain derivations. The
default is ~/.nix-defexpr.
If the argument starts with http:// or https://, it is interpreted as the URL of a
tarball that will be downloaded and unpacked to a temporary location. The tarball must
include a single top-level directory containing at least a file named default.nix.
• --profile / -p path
Specifies the profile to be used by those operations that operate on a profile
(designated below as the active profile). A profile is a sequence of user environments
called generations, one of which is the current generation.
• --dry-run
For the --install, --upgrade, --uninstall, --switch-generation, --delete-generations
and --rollback operations, this flag will cause nix-env to print what would be done if
this flag had not been specified, without actually doing it.
--dry-run also prints out which paths will be substituted (i.e., downloaded) and which
paths will be built from source (because no substitute is available).
• --system-filter system
By default, operations such as --query --available show derivations matching any
platform. This option allows you to use derivations for the specified platform system.
Common Options
Most Nix commands accept the following command-line options:
• --help
Prints out a summary of the command syntax and exits.
• --version
Prints out the Nix version number on standard output and exits.
• --verbose / -v
Increases the level of verbosity of diagnostic messages printed on standard error. For
each Nix operation, the information printed on standard output is well-defined; any
diagnostic information is printed on standard error, never on standard output.
This option may be specified repeatedly. Currently, the following verbosity levels
exist:
• 0 “Errors only”
Only print messages explaining why the Nix invocation failed.
• 1 “Informational”
Print useful messages about what Nix is doing. This is the default.
• 2 “Talkative”
Print more informational messages.
• 3 “Chatty”
Print even more informational messages.
• 4 “Debug”
Print debug information.
• 5 “Vomit”
Print vast amounts of debug information.
• --quiet
Decreases the level of verbosity of diagnostic messages printed on standard error.
This is the inverse option to -v / --verbose.
This option may be specified repeatedly. See the previous verbosity levels list.
• --log-format format
This option can be used to change the output of the log format, with format being one
of:
• raw
This is the raw format, as outputted by nix-build.
• internal-json
Outputs the logs in a structured manner.
Warning
While the schema itself is relatively stable, the format of the error-messages
(namely of the msg-field) can change between releases.
• bar
Only display a progress bar during the builds.
• bar-with-logs
Display the raw logs, with the progress bar at the bottom.
• --no-build-output / -Q
By default, output written by builders to standard output and standard error is echoed
to the Nix command’s standard error. This option suppresses this behaviour. Note that
the builder’s standard output and error are always written to a log file in
prefix/nix/var/log/nix.
• --max-jobs / -j number
Sets the maximum number of build jobs that Nix will perform in parallel to the
specified number. Specify auto to use the number of CPUs in the system. The default
is specified by the max-jobs configuration setting, which itself defaults to 1. A
higher value is useful on SMP systems or to exploit I/O latency.
Setting it to 0 disallows building on the local machine, which is useful when you want
builds to happen only on remote builders.
• --cores
Sets the value of the NIX_BUILD_CORES environment variable in the invocation of
builders. Builders can use this variable at their discretion to control the maximum
amount of parallelism. For instance, in Nixpkgs, if the derivation attribute
enableParallelBuilding is set to true, the builder passes the -jN flag to GNU Make. It
defaults to the value of the cores configuration setting, if set, or 1 otherwise. The
value 0 means that the builder should use all available CPU cores in the system.
• --max-silent-time
Sets the maximum number of seconds that a builder can go without producing any data on
standard output or standard error. The default is specified by the max-silent-time
configuration setting. 0 means no time-out.
• --timeout
Sets the maximum number of seconds that a builder can run. The default is specified by
the timeout configuration setting. 0 means no timeout.
• --keep-going / -k
Keep going in case of failed builds, to the greatest extent possible. That is, if
building an input of some derivation fails, Nix will still build the other inputs, but
not the derivation itself. Without this option, Nix stops if any build fails (except
for builds of substitutes), possibly killing builds in progress (in case of parallel or
distributed builds).
• --keep-failed / -K
Specifies that in case of a build failure, the temporary directory (usually in /tmp) in
which the build takes place should not be deleted. The path of the build directory is
printed as an informational message.
• --fallback
Whenever Nix attempts to build a derivation for which substitutes are known for each
output path, but realising the output paths through the substitutes fails, fall back on
building the derivation.
The most common scenario in which this is useful is when we have registered substitutes
in order to perform binary distribution from, say, a network repository. If the
repository is down, the realisation of the derivation will fail. When this option is
specified, Nix will build the derivation instead. Thus, installation from binaries
falls back on installation from source. This option is not the default since it is
generally not desirable for a transient failure in obtaining the substitutes to lead to
a full build from source (with the related consumption of resources).
• --readonly-mode
When this option is used, no attempt is made to open the Nix database. Most Nix
operations do need database access, so those operations will fail.
• --arg name value
This option is accepted by nix-env, nix-instantiate, nix-shell and nix-build. When
evaluating Nix expressions, the expression evaluator will automatically try to call
functions that it encounters. It can automatically call functions for which every
argument has a default value (e.g., { argName ? defaultValue }: ...).
With --arg, you can also call functions that have arguments without a default value (or
override a default value). That is, if the evaluator encounters a function with an
argument named name, it will call it with value value.
For instance, the top-level default.nix in Nixpkgs is actually a function:
{ # The system (e.g., `i686-linux') for which to build the packages.
system ? builtins.currentSystem
...
}: ...
So if you call this Nix expression (e.g., when you do nix-env --install --attr
pkgname), the function will be called automatically using the value
builtins.currentSystem for the system argument. You can override this using --arg,
e.g., nix-env --install --attr pkgname --arg system \"i686-freebsd\". (Note that
since the argument is a Nix string literal, you have to escape the quotes.)
• --argstr name value
This option is like --arg, only the value is not a Nix expression but a string. So
instead of --arg system \"i686-linux\" (the outer quotes are to keep the shell happy)
you can say --argstr system i686-linux.
• --attr / -A attrPath
Select an attribute from the top-level Nix expression being evaluated. (nix-env, nix-
instantiate, nix-build and nix-shell only.) The attribute path attrPath is a sequence
of attribute names separated by dots. For instance, given a top-level Nix expression
e, the attribute path xorg.xorgserver would cause the expression e.xorg.xorgserver to
be used. See nix-env --install for some concrete examples.
In addition to attribute names, you can also specify array indices. For instance, the
attribute path foo.3.bar selects the bar attribute of the fourth element of the array
in the foo attribute of the top-level expression.
• --expr / -E
Interpret the command line arguments as a list of Nix expressions to be parsed and
evaluated, rather than as a list of file names of Nix expressions. (nix-instantiate,
nix-build and nix-shell only.)
For nix-shell, this option is commonly used to give you a shell in which you can build
the packages returned by the expression. If you want to get a shell which contain the
built packages ready for use, give your expression to the nix-shell --packages
convenience flag instead.
• -I path
Add an entry to the Nix expression search path. This option may be given multiple
times. Paths added through -I take precedence over NIX_PATH.
• --option name value
Set the Nix configuration option name to value. This overrides settings in the Nix
configuration file (see nix.conf5).
• --repair
Fix corrupted or missing store paths by redownloading or rebuilding them. Note that
this is slow because it requires computing a cryptographic hash of the contents of
every path in the closure of the build. Also note the warning under nix-store
--repair-path.
Environment variables
• NIX_PROFILE
Location of the Nix profile. Defaults to the target of the symlink ~/.nix-profile, if
it exists, or /nix/var/nix/profiles/default otherwise.
Common Environment Variables
Most Nix commands interpret the following environment variables:
• IN_NIX_SHELL
Indicator that tells if the current environment was set up by nix-shell. It can have
the values pure or impure.
• NIX_PATH
A colon-separated list of directories used to look up the location of Nix expressions
using paths enclosed in angle brackets (i.e., <path>), e.g. /home/eelco/Dev:/etc/nixos.
It can be extended using the -I option.
If NIX_PATH is not set at all, Nix will fall back to the following list in impure and
unrestricted evaluation mode:
1. $HOME/.nix-defexpr/channels
2. nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs
3. /nix/var/nix/profiles/per-user/root/channels
If NIX_PATH is set to an empty string, resolving search paths will always fail. For
example, attempting to use <nixpkgs> will produce:
error: file 'nixpkgs' was not found in the Nix search path
• NIX_IGNORE_SYMLINK_STORE
Normally, the Nix store directory (typically /nix/store) is not allowed to contain any
symlink components. This is to prevent “impure” builds. Builders sometimes
“canonicalise” paths by resolving all symlink components. Thus, builds on different
machines (with /nix/store resolving to different locations) could yield different
results. This is generally not a problem, except when builds are deployed to machines
where /nix/store resolves differently. If you are sure that you’re not going to do
that, you can set NIX_IGNORE_SYMLINK_STORE to 1.
Note that if you’re symlinking the Nix store so that you can put it on another file
system than the root file system, on Linux you’re better off using bind mount points,
e.g.,
$ mkdir /nix
$ mount -o bind /mnt/otherdisk/nix /nix
Consult the mount 8 manual page for details.
• NIX_STORE_DIR
Overrides the location of the Nix store (default prefix/store).
• NIX_DATA_DIR
Overrides the location of the Nix static data directory (default prefix/share).
• NIX_LOG_DIR
Overrides the location of the Nix log directory (default prefix/var/log/nix).
• NIX_STATE_DIR
Overrides the location of the Nix state directory (default prefix/var/nix).
• NIX_CONF_DIR
Overrides the location of the system Nix configuration directory (default
prefix/etc/nix).
• NIX_CONFIG
Applies settings from Nix configuration from the environment. The content is treated
as if it was read from a Nix configuration file. Settings are separated by the newline
character.
• NIX_USER_CONF_FILES
Overrides the location of the Nix user configuration files to load from.
The default are the locations according to the XDG Base Directory Specification. See
the XDG Base Directories sub-section for details.
The variable is treated as a list separated by the : token.
• TMPDIR
Use the specified directory to store temporary files. In particular, this includes
temporary build directories; these can take up substantial amounts of disk space. The
default is /tmp.
• NIX_REMOTE
This variable should be set to daemon if you want to use the Nix daemon to execute Nix
operations. This is necessary in multi-user Nix installations. If the Nix daemon’s Unix
socket is at some non-standard path, this variable should be set to
unix://path/to/socket. Otherwise, it should be left unset.
• NIX_SHOW_STATS
If set to 1, Nix will print some evaluation statistics, such as the number of values
allocated.
• NIX_COUNT_CALLS
If set to 1, Nix will print how often functions were called during Nix expression
evaluation. This is useful for profiling your Nix expressions.
• GC_INITIAL_HEAP_SIZE
If Nix has been configured to use the Boehm garbage collector, this variable sets the
initial size of the heap in bytes. It defaults to 384 MiB. Setting it to a low value
reduces memory consumption, but will increase runtime due to the overhead of garbage
collection.
XDG Base Directories
Nix follows the XDG Base Directory Specification.
For backwards compatibility, Nix commands will follow the standard only when use-xdg-base-
directories is enabled. New Nix commands (experimental) conform to the standard by
default.
The following environment variables are used to determine locations of various state and
configuration files:
• [XDG_CONFIG_HOME]{#env-XDGCONFIGHOME} (default ~/.config)
• [XDG_STATE_HOME]{#env-XDGSTATEHOME} (default ~/.local/state)
• [XDG_CACHE_HOME]{#env-XDGCACHEHOME} (default ~/.cache)
Examples
To show installed packages:
$ nix-env --query
bison-1.875c
docbook-xml-4.2
firefox-1.0.4
MPlayer-1.0pre7
ORBit2-2.8.3
…
To show available packages:
$ nix-env --query --available
firefox-1.0.7
GConf-2.4.0.1
MPlayer-1.0pre7
ORBit2-2.8.3
…
To show the status of available packages:
$ nix-env --query --available --status
-P- firefox-1.0.7 (not installed but present)
--S GConf-2.4.0.1 (not present, but there is a substitute for fast installation)
--S MPlayer-1.0pre3 (i.e., this is not the installed MPlayer, even though the version is the same!)
IP- ORBit2-2.8.3 (installed and by definition present)
…
To show available packages in the Nix expression foo.nix:
$ nix-env --file ./foo.nix --query --available
foo-1.2.3
To compare installed versions to what’s available:
$ nix-env --query --compare-versions
...
acrobat-reader-7.0 - ? (package is not available at all)
autoconf-2.59 = 2.59 (same version)
firefox-1.0.4 < 1.0.7 (a more recent version is available)
...
To show all packages with “zip” in the name:
$ nix-env --query --available '.*zip.*'
bzip2-1.0.6
gzip-1.6
zip-3.0
…
To show all packages with “firefox” or “chromium” in the name:
$ nix-env --query --available '.*(firefox|chromium).*'
chromium-37.0.2062.94
chromium-beta-38.0.2125.24
firefox-32.0.3
firefox-with-plugins-13.0.1
…
To show all packages in the latest revision of the Nixpkgs repository:
$ nix-env --file https://github.com/NixOS/nixpkgs/archive/master.tar.gz --query --available
nix-env –query(1)