# dpkg manual page - deb-substvars(5)
#
# Copyright © 1995-1996 Ian Jackson <ijackson@chiark.greenend.org.uk>
# Copyright © 2000 Wichert Akkerman <wakkerma@debian.org>
# Copyright © 2006-2009,2012-2015 Guillem Jover <guillem@debian.org>
# Copyright © 2009-2010 Raphaël Hertzog <hertzog@debian.org>
#
# This is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

=encoding utf8

=head1 NAME

deb-substvars - Debian source substitution variables

=head1 SYNOPSIS

B<debian/substvars>, B<debian/>I<binary-package>B<.substvars>, variables

=head1 DESCRIPTION

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

=head2 Variable Syntax

A variable substitution has the form
B<${>I<variable-name>B<}>.
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.

=head2 File Syntax

Substitution variables can be specified in a file.
These files consist of lines with variable assignments,
that start with the variable name,
immediately followed by an assignment operator,
and then the value.
Each operator gives the variable specific attributes.
Trailing whitespace on each line, blank lines, and lines starting with a
B<#> symbol (comments) are ignored.

The following operators are supported:

=over

=item B<=>

Assigns a normal substitution variable.

=item B<?=>

Assigns an optional substitution variable which will emit no warnings
even if unused.

Supported since dpkg 1.21.8.

=item B<!=>

Assigns a required substitution variable which will error out if unused.

Supported since dpkg 1.22.7.

=item B<$=>

Assigns an implicit substitution variable which will get automatically
instantiated as a field,
if that field is not defined for B<.dsc> and B<.deb> control files.

The variable name needs to be formed as a namespace followed by
a colon (‘B<:>’) and then the field name,
such as B<tool:Depends>.
All implicit variables for any namespace matching the same field
will get concatenated using a known field separator,
or a space if the field separator is unknown.

Supported since dpkg 1.23.0.

=back

For example C<some-package:Depends?=other-package (= 1.0), the-package>.

=head2 Substitution

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

After all the substitutions have been done each occurrence of the
string
B<${}>
(which is not an actual substitution variable) is replaced with a
B<$>
sign.
This can be used as an escape sequence such as B<${}{>I<VARIABLE>B<}> which
will end up as B<${>I<VARIABLE>B<}> 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 B<Package>,
B<Source> and B<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
B<${Description}> is set to "foo is bar.${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.

=head2 Built-in Variable

Additionally, the following standard variables are always available:

=over

=item B<Arch>

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

=item B<vendor:Name>

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

=item B<vendor:Id>

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

=item B<source:Version>

The source package version (since dpkg 1.13.19).

=item B<source:Upstream-Version>

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

=item B<binary:Version>

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

=item B<Source-Version>

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

=item B<source:Synopsis>

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

=item B<source:Extended-Description>

The source package extended description, extracted from the source stanza
B<Description> field, if it exists (since dpkg 1.19.0).

=item B<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
B<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.

B<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.

=item B<Extra-Size>

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

=item B<S:>I<field-name>

The value of the source stanza field
I<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.

=item B<F:>I<field-name>

The value of the output field
I<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.

=item B<Format>

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

=item B<Newline>, B<Space>, B<Tab>

These variables each hold the corresponding character.

=item B<shlibs:>I<dependencyfield>

Variable settings with names of this form are generated by
B<dpkg-shlibdeps>.

=item B<dpkg:Upstream-Version>

The upstream version of dpkg (since dpkg 1.13.19).

=item B<dpkg:Version>

The full version of dpkg (since dpkg 1.13.19).

=back

=head1 FILES

=over

=item B<debian/substvars>

List of substitution variables and values.

=back

=head1 SEE ALSO

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