deb-substvars(5) dpkg suite deb-substvars(5)
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).
1.22.21 2025-06-30 deb-substvars(5)
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