NAME

       deb-substvars - Debian source substitution variables

SYNOPSIS

       debian/substvars, debian/binary-package.substvars, variables

DESCRIPTION

       Before dpkg-source, dpkg-gencontrol and dpkg-genchanges write their control information
       (to the source control file .dsc for dpkg-source and to standard output for dpkg-
       gencontrol and dpkg-genchanges) they perform some variable substitutions on the output
       file.

   Variable Syntax
       A variable substitution has the form ${variable-name}.  Variable names consist of
       alphanumerics (a-zA-Z0-9), hyphens (-) and colons (:) and start with an alphanumeric, and
       are case-sensitive, even though they might refer to other entities which are case-
       preserving.  Variable substitutions are performed repeatedly until none are left; the full
       text of the field after the substitution is rescanned to look for more substitutions.

   File Syntax
       Substitution variables can be specified in a file.  These files consist of lines of the
       form name=value, name?=value, or name!=value.  The = operator assigns a normal
       substitution variable, the ?= operator (since dpkg 1.21.8) assigns an optional
       substitution variable which will emit no warnings even if unused, and the != operator
       (since dpkg 1.22.7) assigns a required substitution variable which will error out if
       unused.  Trailing whitespace on each line, blank lines, and lines starting with a # symbol
       (comments) are ignored.

   Substitution
       Variables can be set using the -V common option.  They can be also specified in the file
       debian/substvars (or whatever other file is specified using the -T common option).

       After all the substitutions have been done each occurrence of the string ${} (which is not
       an actual substitution variable) is replaced with a $ sign.  This can be used as an escape
       sequence such as ${}{VARIABLE} which will end up as ${VARIABLE} on the output.

       If a variable is referred to but not defined it generates a warning and an empty value is
       assumed.

       While variable substitution is done on all control fields, some of those fields are used
       and needed during the build when the substitution did not yet occur.  That's why you can't
       use variables in the Package, Source and Architecture fields.

       Variable substitution happens on the content of the fields after they have been parsed,
       thus if you want a variable to expand over multiple lines you do not have to include a
       space after the newline.  This is done implicitly when the field is output.  For example,
       if the variable ${Description} is set to "foo is bar.${Newline}foo is great." and if you
       have the following field:

        Description: foo application
         ${Description}
         .
         More text.

       It will result in:

        Description: foo application
         foo is bar.
         foo is great.
         .
         More text.

   Built-in Variable
       Additionally, the following standard variables are always available:

       Arch
           The current host architecture (i.e. the architecture the package is being built for,
           the equivalent of DEB_HOST_ARCH).

       vendor:Name
           The current vendor name (since dpkg 1.20.0).  This value comes from the Vendor field
           for the current vendor's origin file, as dpkg-vendor(1) would retrieve it.

       vendor:Id
           The current vendor ID (since dpkg 1.20.0).  This is just the lowercase variant of
           vendor:Name.

       source:Version
           The source package version (since dpkg 1.13.19).

       source:Upstream-Version
           The upstream source package version, including the Debian version epoch if any (since
           dpkg 1.13.19).

       binary:Version
           The binary package version (which may differ from source:Version in a binNMU for
           example; since dpkg 1.13.19).

       Source-Version
           The source package version (from the changelog file).  This variable is now obsolete
           and emits an error when used as its meaning is different from its function, please use
           the source:Version or binary:Version as appropriate.

       source:Synopsis
           The source package synopsis, extracted from the source stanza Description field, if it
           exists (since dpkg 1.19.0).

       source:Extended-Description
           The source package extended description, extracted from the source stanza Description
           field, if it exists (since dpkg 1.19.0).

       Installed-Size
           The approximate total size of the package's installed files.  This value is copied
           into the corresponding control file field; setting it will modify the value of that
           field.  If this variable is not set dpkg-gencontrol will compute the default value by
           accumulating the size of each regular file and symlink rounded to 1 KiB used units,
           and a baseline of 1 KiB for any other filesystem object type.  With hardlinks only
           being counted once as a regular file.

           Note: Take into account that this can only ever be an approximation, as the actual
           size used on the installed system will depend greatly on the filesystem used and its
           parameters, which might end up using either more or less space than the specified in
           this field.

       Extra-Size
           Additional disk space used when the package is installed.  If this variable is set its
           value is added to that of the Installed-Size variable (whether set explicitly or using
           the default value) before it is copied into the Installed-Size control file field.

       S:field-name
           The value of the source stanza field field-name (which must be given in the canonical
           capitalization; since dpkg 1.18.11).  Setting these variables has no effect other than
           on places where they are expanded explicitly.  These variables are only available when
           generating binary control files.

       F:field-name
           The value of the output field field-name (which must be given in the canonical
           capitalization).  Setting these variables has no effect other than on places where
           they are expanded explicitly.

       Format
           The .changes file format version generated by this version of the source packaging
           scripts.  If you set this variable the contents of the Format field in the .changes
           file will change too.

       Newline, Space, Tab
           These variables each hold the corresponding character.

       shlibs:dependencyfield
           Variable settings with names of this form are generated by dpkg-shlibdeps.

       dpkg:Upstream-Version
           The upstream version of dpkg (since dpkg 1.13.19).

       dpkg:Version
           The full version of dpkg (since dpkg 1.13.19).

FILES

       debian/substvars
           List of substitution variables and values.

SEE ALSO

       dpkg(1), dpkg-vendor(1), dpkg-genchanges(1), dpkg-gencontrol(1), dpkg-shlibdeps(1),
       dpkg-source(1).