.\" dpkg manual page - deb-substvars(5)
.\"
.\" Copyright © 1995-1996 Ian Jackson <ijackson@chiark.greenend.org.uk>
.\" Copyright © 2000 Wichert Akkerman <wakkerma@debian.org>
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.
.TH deb\-substvars 5 "2022-05-25" "1.19.7" "dpkg suite"
.nh
.SH NAME
deb\-substvars \- Debian source substitution variables
.
.SH SYNOPSIS
substvars
.
.SH DESCRIPTION
Before
.BR dpkg\-source ", " dpkg\-gencontrol " and " dpkg\-genchanges
write their control information (to the source control file
.B .dsc
for
.B dpkg\-source
and to standard output for
.BR dpkg\-gencontrol " and " dpkg\-genchanges )
they perform some variable substitutions on the output file.

A variable substitution has the form
.BI ${ variable-name }\fR.
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.

After all the substitutions have been done each occurrence of the
string
.B ${}
(which is not a legal substitution) is replaced with a
.B $
sign.

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 \fBPackage\fP,
\fBSource\fP and \fBArchitecture\fP 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
\fB${Description}\fP is set to "foo is bar.${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.

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
option). This file consists of lines of the form
.IB name = value\fR.
Trailing whitespace on each line, blank lines, and
lines starting with a
.B #
symbol (comments) are ignored.

Additionally, the following standard variables are available:
.TP
.BI Arch
The current host architecture (i.e. the architecture the package is being
built for, the equivalent of \fBDEB_HOST_ARCH\fP).
.TP
.B source:Version
The source package version (since dpkg 1.13.19).
.TP
.B source:Upstream\-Version
The upstream source package version, including the Debian version epoch if
any (since dpkg 1.13.19).
.TP
.B binary:Version
The binary package version (which may differ from \fBsource:Version\fP in
a binNMU for example; since dpkg 1.13.19).
.TP
.B Source\-Version
The source package version (from the changelog file). This variable is now
\fBobsolete\fP and emits an error when used as its meaning is different from
its function, please use the \fBsource:Version\fP or \fBbinary:Version\fP as
appropriate.
.TP
.B source:Synopsis
The source package synopsis, extracted from the source stanza
\fBDescription\fP field, if it exists (since dpkg 1.19.0).
.TP
.B source:Extended\-Description
The source package extended description, extracted from the source stanza
\fBDescription\fP field, if it exists (since dpkg 1.19.0).
.TP
.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.

\fBNote:\fP 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.
.TP
.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.
.TP
.BI S: fieldname
The value of the source stanza field
.I fieldname
(which must be given in the canonical capitalisation; 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.
.TP
.BI F: fieldname
The value of the output field
.IR fieldname
(which must be given in the canonical capitalisation). Setting these
variables has no effect other than on places where they are expanded
explicitly.
.TP
.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.
.TP
.BR Newline ", " Space ", " Tab
These variables each hold the corresponding character.
.TP
.BI shlibs: dependencyfield
Variable settings with names of this form are generated by
.BR dpkg\-shlibdeps .
.TP
.B dpkg:Upstream\-Version
The upstream version of dpkg (since dpkg 1.13.19).
.TP
.B dpkg:Version
The full version of dpkg (since dpkg 1.13.19).
.LP
If a variable is referred to but not defined it generates a warning
and an empty value is assumed.
.
.SH FILES
.TP
.B debian/substvars
List of substitution variables and values.
.
.SH SEE ALSO
.ad l
.BR dpkg (1),
.BR dpkg\-genchanges (1),
.BR dpkg\-gencontrol (1),
.BR dpkg\-shlibdeps (1),
.BR dpkg\-source (1).
