NAME    [Toc]    [Back]

       dpkg-architecture - set and determine the architecture for package
       building

SYNOPSIS    [Toc]    [Back]

       dpkg-architecture [options] [action]

       Valid options: -aDebian-Architecture -tGnu-System-Type -f

       Valid actions: -l, -qVariable-Name, -s, -u, -c Command

DESCRIPTION    [Toc]    [Back]

       dpkg-architecture does provide a facility to determine and set the
       build and host architecture for package building.

OVERVIEW    [Toc]    [Back]

       The build architecture is always determined by an external call to
       dpkg, and can not be set at the command line.

       You can specify the host architecture by providing one or both of the
       options -a and -t. The default is determined by an external call to
       gcc, or the same as the build architecture if CC or gcc are both not
       available. One out of -a and -t is sufficient, the value of the other
       will be set to a usable default.  Indeed, it is often better to only
       specify one, because dpkg-architecture will warn you if your choice
       doesn't match the default.

       The default action is -l, which prints the environment variales, one
       each line, in the format VARIABLE=value. If you are only interested in
       the value of a single variable, you can use -q. If you specify -s, it
       will output an export command. This can be used to set the environment
       variables using eval. -u does return a similar command to unset all
       variables. -c does execute a command in an environment which has all
       variables set to the determined value.

       Existing environment variables with the same name as used by the
       scripts are not overwritten, except if the -f force flag is present.
       This allows the user to override a value even when the call to dpkgarchitecture
 is buried in some other script (for example dpkg-buildpackage).

TERMS    [Toc]    [Back]

       build machine
	   The machine the package is build on.

       host machine
	   The machine the package is build for.

       Debian Architecture
	   The Debian archietcture string, which specifies the binary tree in
	   the FTP archive. Examples: i386, sparc, hurd-i386.

       GNU System Type
	   An architecture specification string consisting of two or three
	   parts, cpu-system or cpu-vendor-system. Examples: i386-linux,
	   sparc-linux, i386-gnu.

EXAMPLES    [Toc]    [Back]

       dpkg-buildpackage accepts the -a option and passes it to dpkg-architecture.
  Other examples:

       CC=i386-gnu-gcc dpkg-architecture "-c" debian/rules build

       eval `dpkg-architecture "-u"`

VARIABLES    [Toc]    [Back]

       The following variables are set by dpkg-architecture:

       DEB_BUILD_ARCH
	   The Debian architecture of the build machine.

       DEB_BUILD_GNU_TYPE
	   The GNU system type of the build machine.

       DEB_BUILD_GNU_CPU
	   The CPU part of DEB_BUILD_GNU_TYPE

       DEB_BUILD_GNU_SYSTEM
	   The System part of DEB_BUILD_GNU_TYPE

       DEB_HOST_ARCH
	   The Debian architecture of the host machine.

       DEB_HOST_GNU_TYPE
	   The GNU system type of the host machine.

       DEB_HOST_GNU_CPU
	   The CPU part of DEB_HOST_GNU_TYPE

       DEB_HOST_GNU_SYSTEM
	   The System part of DEB_HOST_GNU_TYPE

DEBIAN/RULES
       The environment variables set by dpkg-architecture are passed to
       debian/rules as make variables (see make documentation). You can and
       should use them in the build process as needed. Here are some examples,
       which also show how you can improve the cross compilation support in
       your package:

       Instead:

       ARCH=`dpkg --print-architecture` configure $(ARCH)-linux

       please use the following:

       B_ARCH=$(DEB_BUILD_GNU_TYPE) H_ARCH=$(DEB_HOST_GNU_TYPE) configure
       --build=$(B_ARCH) --host=$(H_ARCH)

       Instead:

       ARCH=`dpkg --print-architecture` ifeq ($(ARCH),alpha)
	 ...  endif

       please use:

       ARCH=$(DEB_HOST_ARCH) ifeq ($(ARCH),alpha)
	 ...  endif

       In general, calling dpkg in the rules file to get architecture information
 is deprecated (until you want to provide backward compatibility,
       see below).  Especially the --print-architecture option is unreliable
       since we have Debian architectures which don't equal a processor name.

BACKWARD COMPATIBILITY    [Toc]    [Back]

       When providing a new facility, it is always a good idea to stay compatible
 with old versions of the programs. Note that dpkg-architecture
       does not affect old debian/rules files, so the only thing to consider
       is using old building scripts with new debian/rules files. The following
 does the job:

       DEB_BUILD_ARCH := $(shell dpkg --print-installation-architecture)
       DEB_BUILD_GNU_CPU := $(patsubst hurd-%,%,$(DEB_BUILD_ARCH)) ifeq
       ($(filter-out hurd-%,$(DEB_BUILD_ARCH)),)
	 DEB_BUILD_GNU_SYSTEM := gnu else
	 DEB_BUILD_GNU_SYSTEM := linux endif
       DEB_BUILD_GNU_TYPE=$(DEB_BUILD_GNU_CPU)-$(DEB_BUILD_GNU_SYSTEM)

       DEB_HOST_ARCH=$(DEB_BUILD_ARCH) DEB_HOST_GNU_CPU=$(DEB_BUILD_GNU_CPU)
       DEB_HOST_GNU_SYSTEM=$(DEB_BUILD_GNU_SYSTEM)
       DEB_HOST_GNU_TYPE=$(DEB_BUILD_GNU_TYPE)

       Put a subset of these lines at the top of your debian/rules file; these
       default values will be overwritten if dpkg-architecture is used.

       You don't need the full set. Choose a consistent set which contains the
       values you use in the rules file. For example, if you only need the
       host Debian architecture, `DEB_HOST_ARCH=`dpkg --print-installation-architecture`
 is sufficient (this is indeed the Debian architecture
 of the build machine, but remember that we are only trying to be
       backward compatible with native compilation).

       You may not want to care about old build packages (for example, if you
       have sufficient source dependencies declared anyway). But you should at
       least support the traditional way to build packages by calling
       `debian/rules build' directly, without setting environment variables.
       To do this, use the -q option to query suitable default values:

       DEB_BUILD_ARCH=`dpkg-architecture -qDEB_BUILD_ARCH`
       DEB_BUILD_GNU=`dpkg-architecture -qDEB_BUILD_GNU`

       etc. You get the idea. This way, you can ensure that the variables are
       never undeclared. Note that this breaks backwards compatibility with
       old build scripts, and you should only do that if source dependencies
       are implemented and declared accordingly.

SEE ALSO    [Toc]    [Back]

       dpkg-buildpackage dpkg-cross

CONTACT    [Toc]    [Back]

       If you have questions about the usage of the make variables in your
       rules files, or about cross compilation support in your packages,
       please email me.  The address is Marcus Brinkmann <brinkmd@debian.org>.



3rd Berkeley Distribution	  2001-06-20		  DPKG-ARCHITECTURE(1)