deb-substvars(5) Debian source substitution variables




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.

A variable substitution has the form ${variable-name}. Variable names consist of alphanumerics, hyphens and colons and start with an alphanumeric. 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 ${} (which is not a legal substitution) is replaced with a $ 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 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
  More text.

It will result in:

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

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

Additionally, the following standard variables are available:

The current host architecture (i.e. the architecture the package is being built for, the equivalent of DEB_HOST_ARCH).
The source package version.
The upstream source package version, including the Debian version epoch if any.
The binary package version (which may differ from source:Version in a binNMU for example).
The source package version (from the changelog file). This variable is now deprecated as its meaning is different from its function, please use the source:Version or binary:Version as appropriate.
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.

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.

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.
The value of the output field fieldname (which must be given in the canonical capitalisation). Setting these variables has no effect other than on places where they are expanded explicitly.
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.
Variable settings with names of this form are generated by dpkg-shlibdeps.
The upstream version of dpkg.
The full version of dpkg.

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


List of substitution variables and values.