dh_assistant(1) — Linux manual page


DH_ASSISTANT(1)                 Debhelper                DH_ASSISTANT(1)

NAME         top

       dh_assistant - tool for supporting debhelper tools and provide

SYNOPSIS         top

       dh_assistant command [additional options]

DESCRIPTION         top

       dh_assistant is a debhelper program that provides introspection
       into the debhelper stack to assist third-party tools (e.g.
       linters) or third-party debhelper implementations not using the
       debhelper script API (e.g., because they are not written in

COMMANDS         top

       The dh_assistant supports the following commands:

   active-compat-level (JSON)
       Synopsis: dh_assistant active-compat-level

       Outputs information about which compat level the package is

       For packages without valid debhelper compatibility information
       (whether missing, ambiguous, not supported or simply invalid),
       this command operates on a "best effort" basis and may abort when
       error instead of providing data.

       The returned JSON dictionary contains the following key-value

           The compat level that debhelper will be using.  This is the
           same as DH_COMPAT when present or else declared-compat-level.
           This can be null when no compat level can be detected.

           The compat level that the package declared as its default
           compat level.  This can be null if the package does not
           declare any compat level at all.

           Defines how the compat level was declared.  This is null (for
           the same reason as declared-compat-level) or one of:

               The compatibility level was declared in the first line
               debian/compat file.

           Build-Depends: debhelper-compat (= <C>)
               The compatibility was declared in the debian/control via
               a build dependency on the debhelper-compat (= <C>)
               package in the Build-Depends field.  In the output, the C
               is replaced by the actual compatibility level.  A full
               example value would be:

                  Build-Depends: debhelper-compat (= 13)

   supported-compat-levels (JSON, CRFA)
       Synopsis: dh_assistant supported-compat-levels

       Outputs information about which compat levels, this build of
       debhelper knows about.

       This command accepts no options or arguments.

   which-build-system (JSON)
       Synopsis: dh_assistant which-build-system [build step]
       [build system options]

       Output information about which build system would be used for a
       particular build step.  The build step must be one of configure,
       build, test, install or clean and must be the first argument
       after which-build-system when provided.  If omitted, it defaults
       to configure as it is the most reliable step to use auto-
       detection on in a clean source directory.  Note that build steps
       do not always agree when using auto-detection - particularly if
       the configure step has not been run.

       Additionally, the clean step can also provide "surprising"
       results for builds that rely on a separate build directory.  In
       such cases, debhelper will return the first build system that
       uses a separate build directory rather than the one build system
       that configure would detect.  This is generally a cosmetic issue
       as both build systems are all basically a glorified rm -fr
       builddir and more precise detection is functionally irrelevant as
       far as debhelper is concerned.

       The option accepts all debhelper build system arguments - i.e.,
       options you can pass to all of the dh_auto_* commands plus (for
       the install step) the --destdir option.  These options affect the
       output and auto-detection in various ways.  Passing -S or
       --buildsystem overrides the auto-detection (as it does for
       dh_auto_*) but it still provides introspection into the chosen
       build system.

       Things that are useful to know about the output:

       •   The key build-system is the build system that would be used
           by debhelper for the given step (with the given options,
           debhelper compat level, environment variables and the given
           working directory).  When -S and --buildsystem are omitted,
           this is the result of debhelper's auto-detection logic.

           The value is valid as a parameter for the --buildsystem

           The special value none is used to denote that no build system
           would be used.  This value is not present in --list parameter
           for the dh_auto_* commands, but since debhelper/12.9 the
           value is accepted for the --buildsystem option.

           Note that auto-detection is subject to limitations in regards
           to third-party build systems.  While debhelper does support
           auto-detecting some third-party build systems, they must be
           installed for the detection to work.  If they are not
           installed, the detection logic silently skips that build
           system (often resulting in build-system being none in the

       •   The build-directory and buildpath values serve different but
           related purposes.  The build-directory generally mirrors the
           --builddirectory option where as buildpath is the output
           directory that debhelper will use.  Therefore the former will
           often be null when --builddirectory has not been passed while
           the latter will generally not be null (except when build-
           system is none).

       •   The dest-directory (--destdir) is undefined for all build
           steps except the install build step (will be output as null
           or absent).  For the same reason, --destdir should only be
           passed for install build step.

           Note that if not specified, this value is currently null by

       •   The parallel value is subject to DEB_BUILD_OPTIONS.  Notably,
           if that does not include the parallel keyword, then parallel
           field in the output will always be 1.

       •   Most fields in the output can be null.  Particular if there
           is no build system is detected (or when --buildsystem=none).
           Additionally, many of the fields can be null even if there is
           a build system if the build system does not use/set/define
           that variable.

   detect-hook-targets (JSON)
       Synopsis: dh_assistant detect-hook-targets

       Detects possible override targets and hook targets that dh(1)
       might use (provided that the relevant command is in the

       The detection is based on scanning the rules file for any target
       that might look like a hook target and can therefore list targets
       that are in fact not hook targets (or are but will never be
       triggered for other reasons).

       The detection uses a similar logic for scanning the rules file
       and is therefore subject to makefile conditionals (i.e., the
       truth value of makefile conditionals can change whether a hook
       target is visible in the output of this command).  In theory, you
       would have to setup up the environment to look like it would
       during a build for getting the most accurate output.  Though, a
       lot of packages will not have conditional hook targets, so the
       "out of the box" behaviour will work well in most cases.

       The output looks something like this:

              "commands-not-in-path": [
              "hook-targets": [
                    "command": "dh_strip_nondeterminism",
                    "is-empty": true,
                    "package-section-param": null,
                    "target-name": "override_dh_strip_nondeterminism"
                    "command": "dh_foo",
                    "is-empty": false,
                    "package-section-param": "-a",
                    "target-name": "override_dh_foo-arch"

       In more details:

           This attribute lists all the commands related to hook
           targets, which dh_assistant could not find in PATH.  These
           are usually caused by either the command not being installed
           on the system where dh_assistant is run or by the command not
           existing at all.

           If you are using this command to verify an hook target is
           present, please double check that the command is spelled

           List over hook targets found along with additional
           information about them.

               Attribute that lists which command this hook target is
               related too.

               The actual target name detected in the debian/rules file.

               A boolean that determines whether dh(1) will optimize the
               hook out at runtime (see "Completely empty targets" in
               dh(1)). Note that empty override targets will still cause
               dh(1)  to skip the original command.

               This attribute defines what package selection parameter
               should be passed to dh_* commands used in the hook
               target.  It can either be -a, -i or (if no parameter
               should be used) "null".

       This command accepts no options or arguments.

       Synopsis: dh_assistant -ppkg [--on-behalf-of-cmd=dh_foo] path ...

       Mark one or more paths as installed for a given package.  This is
       useful for telling dh_missing(1) that the paths have been
       installed manually.

       The --on-behalf-of-cmd option can be used by third-party tools to
       have dh_assistant list them as the installer of the provided
       paths.  The convention is to use the basename of the tool itself
       as its name (e.g. dh_install).

       Please keep in mind that:

       •   No glob or substitution expansion is done by dh_assistant on
           the provided paths.  If you want to use globs, have the shell
           perform the expansion first.

       •   Paths must be given as relative to the source root directory
           (e.g., debian/tmp/...)

       •   You can provide a directory.  If you do, the directory and
           anything recursively below it will be considered as
           installed.  Note that it is fine to provide the directory
           even if paths inside of it has been excluded as long as the
           directory is fully "covered".

       •   Do not worry about providing the same filename twice in
           different invocations to dh_assistant due to -arch / -indep
           overrides.  While it will be recorded multiple internally,
           dh_missing(1) will deduplicate when it parses the records.

       Note this command only marks paths as installed. It does not
       actually install them - the caller should ensure that the paths
       are in fact handled (or installed).

COMMAND TAGS         top

       Most commands have one or more of the following "tags" associated
       with them.  Their meaning is defined here.

           The command provides JSON output. See "JSON OUTPUT" for

           Mnemonic "Can be Run From Anywhere"

           Most commands must be run inside a source package root
           directory (a directory containing debian/control) because
           debhelper will need the package metadata to lookup the
           information.  Any command with this tag are exempt from this
           requirement and is expected to work regardless of where they
           are run.

JSON OUTPUT         top

       Most commands uses JSON format as output.  Consumers need to be
       aware that:

       •   Additional keys may be added at any time.  For backwards
           compatibility, the absence of a key should in general be
           interpreted as null unless another default is documented or
           would be "obvious" for that case.

       •   Many keys can be null/undefined in special cases.  As an
           example, some information may be unavailable when this
           command is run directly from the debhelper source (git

       The output will be prettified when stdout is detected as a
       terminal.  If you need to pipe the output to a pager/file (etc.)
       and still want it prettified, please use an external JSON
       formatter. An example of this:

            dh_assistant supported-compat-levels | json_pp | less

SEE ALSO         top


       This program is a part of debhelper.

COLOPHON         top

       This page is part of the debhelper (helper programs for
       debian/rules) project.  Information about the project can be
       found at [unknown -- if you know, please contact man-
       pages@man7.org] If you have a bug report for this manual page,
       send it to submit@bugs.debian.org.  This page was obtained from
       the project's upstream Git repository
       ⟨https://salsa.debian.org/debian/debhelper.git⟩ on 2023-06-23.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-03-05.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

13.11.1                        2022-12-14                DH_ASSISTANT(1)

Pages that refer to this page: dh(1)debhelper(7)