Attributes

name

This is a string, with a minimum of 2 and a maximum of 50 characters (though shorter names are recommended), that defines the package name. It will be the <PkgName>/version@user/channel of the package reference. It should match the following regex ^[a-zA-Z0-9_][a-zA-Z0-9_\+\.-]$, so start with alphanumeric or underscore, then alphanumeric, underscore, +, ., - characters.

The name is only necessary for export-ing the recipe into the local cache (export and create commands), if they are not defined in the command line. It might take its value from an environment variable, or even any python code that defines it (e.g. a function that reads an environment variable, or a file from disk). However, the most common and suggested approach would be to define it in plain text as a constant, or provide it as command line arguments.

version

The version attribute will define the version part of the package reference: PkgName/<version>@user/channel It is a string, and can take any value, matching the same constraints as the name attribute. In case the version follows semantic versioning in the form X.Y.Z-pre1+build2, that value might be used for requiring this package through version ranges instead of exact versions.

The version is only strictly necessary for export-ing the recipe into the local cache (export and create commands), if they are not defined in the command line. It might take its value from an environment variable, or even any python code that defines it (e.g. a function that reads an environment variable, or a file from disk). Please note that this value might be used in the recipe in other places (as in source() method to retrieve code from elsewhere), making this value not constant means that it may evaluate differently in different contexts (e.g., on different machines or for different users) leading to unrepeatable or unpredictable results. The most common and suggested approach would be to define it in plain text as a constant, or provide it as command line arguments.

description

This is an optional, but strongly recommended text field, containing the description of the package, and any information that might be useful for the consumers. The first line might be used as a short description of the package.

class HelloConan(ConanFile):
    name = "Hello"
    version = "0.1"
    description = """This is a Hello World library.
                    A fully featured, portable, C++ library to say Hello World in the stdout,
                    with incredible iostreams performance"""

homepage

Use this attribute to indicate the home web page of the library being packaged. This is useful to link the recipe to further explanations of the library itself like an overview of its features, documentation, FAQ as well as other related information.

class EigenConan(ConanFile):
    name = "eigen"
    version = "3.3.4"
    homepage = "http://eigen.tuxfamily.org"

url

It is possible, even typical, if you are packaging a third party lib, that you just develop the packaging code. Such code is also subject to change, often via collaboration, so it should be stored in a VCS like git, and probably put on GitHub or a similar service. If you do indeed maintain such a repository, please indicate it in the url attribute, so that it can be easily found.

class HelloConan(ConanFile):
    name = "Hello"
    version = "0.1"
    url = "https://github.com/memsharded/hellopack.git"

The url is the url of the package repository, i.e. not necessarily the original source code. It is optional, but highly recommended, that it points to GitHub, Bitbucket or your preferred code collaboration platform. Of course, if you have the conanfile inside your library source, you can point to it, and afterwards use the url in your source() method.

This is a recommended, but not mandatory attribute.

license

This field is intended for the license of the target source code and binaries, i.e. the code that is being packaged, not the conanfile.py itself. This info is used to be displayed by the conan info command and possibly other search and report tools.

class HelloConan(ConanFile):
    name = "Hello"
    version = "0.1"
    license = "MIT"

This attribute can contain several, comma separated licenses. It is a text string, so it can contain any text, including hyperlinks to license files elsewhere.

However, we strongly recommend packagers of Open-Source projects to use [SPDX](https://spdx.org/) identifiers from the [SPDX license list](https://spdx.org/licenses/) instead of free-formed text. This will help people wanting to automate license compatibility checks, like consumers of your package, or you if your package has Open-Source dependencies.

This is a recommended, but not mandatory attribute.

author

Intended to add information about the author, in case it is different from the Conan user. It is possible that the Conan user is the name of an organization, project, company or group, and many users have permissions over that account. In this case, the author information can explicitly define who is the creator/maintainer of the package

class HelloConan(ConanFile):
    name = "Hello"
    version = "0.1"
    author = "John J. Smith (john.smith@company.com)"

This is an optional attribute.

topics

Topics provide a useful way to group related tags together and to quickly tell developers what a package is about. Topics also make it easier for customers to find your recipe. It could be useful to filter packages by topics or to reuse them in Bintray package page.

The topics attribute should be a tuple with the needed topics inside.

class ProtocInstallerConan(ConanFile):
    name = "protoc_installer"
    version = "0.1"
    topics = ("protocol-buffers", "protocol-compiler", "serialization", "rpc")

This is an optional attribute.

user, channel

The fields user and channel can be accessed from within a conanfile.py. Though their usage is usually not encouraged, it could be useful in different cases, e.g. to define requirements with the same user and channel than the current package, which could be achieved with something like:

from conans import ConanFile

class HelloConan(ConanFile):
    name = "Hello"
    version = "0.1"

    def requirements(self):
        self.requires("Say/0.1@%s/%s" % (self.user, self.channel))

Only package recipes that are in the conan local cache (i.e. “exported”) have a user/channel assigned. For package recipes working in user space, there is no current user/channel by default. They can be defined at conan install time with:

$ conan install <path to conanfile.py> user/channel

If they are not defined via command line, the properties self.user and self.channel will then look for environment variables CONAN_USERNAME and CONAN_CHANNEL respectively. If they are not defined, an error will be raised unless default_user and default_channel are declared in the recipe.

See also

FAQ: Is there any recommendation regarding which <user> or <channel> to use in a reference?

default_user, default_channel

For package recipes working in the user space, with local methods like conan install . and conan build ., there is no current user/channel. If you are accessing to self.user or self.channel in your recipe, you need to declare the environment variables CONAN_USERNAME and CONAN_CHANNEL or you can set the attributes default_user and default_channel. You can also use python @properties:

from conans import ConanFile

class HelloConan(ConanFile):
    name = "Hello"
    version = "0.1"
    default_user = "myuser"

    @property
    def default_channel(self):
        return "mydefaultchannel"

    def requirements(self):
        self.requires("Pkg/0.1@%s/%s" % (self.user, self.channel))

settings

There are several things that can potentially affect a package being created, i.e. the final package will be different (a different binary, for example), if some input is different.

Development project-wide variables, like the compiler, its version, or the OS itself. These variables have to be defined, and they cannot have a default value listed in the conanfile, as it would not make sense.

It is obvious that changing the OS produces a different binary in most cases. Changing the compiler or compiler version changes the binary too, which might have a compatible ABI or not, but the package will be different in any case.

For these reasons, the most common convention among Conan recipes is to distinguish binaries by the following four settings, which is reflected in the conanfile.py template used in the conan new command:

settings = "os", "compiler", "build_type", "arch"

When Conan generates a compiled binary for a package with a given combination of the settings above, it generates a unique ID for that binary by hashing the current values of these settings.

But what happens for example to header only libraries? The final package for such libraries is not binary and, in most cases it will be identical, unless it is automatically generating code. We can indicate that in the conanfile:

from conans import ConanFile

 class HelloConan(ConanFile):
     name = "Hello"
     version = "0.1"
     # We can just omit the settings attribute too
     settings = None

     def build(self):
         #empty too, nothing to build in header only

You can restrict existing settings and accepted values as well, by redeclaring the settings attribute:

class HelloConan(ConanFile):
    settings = {"os": ["Windows"],
        "compiler": {"Visual Studio": {"version": [11, 12]}},
        "arch": None}

In this example we have just defined that this package only works in Windows, with VS 10 and 11. Any attempt to build it in other platforms with other settings will throw an error saying so. We have also defined that the runtime (the MD and MT flags of VS) is irrelevant for us (maybe we using a universal one?). Using None as a value means, maintain the original values in order to avoid re-typing them. Then, “arch”: None is totally equivalent to “arch”: [“x86”, “x86_64”, “arm”] Check the reference or your ~/.conan/settings.yml file.

As re-defining the whole settings attribute can be tedious, it is sometimes much simpler to remove or tune specific fields in the configure() method. For example, if our package is runtime independent in VS, we can just remove that setting field:

settings = "os", "compiler", "build_type", "arch"

def configure(self):
    self.settings.compiler["Visual Studio"].remove("runtime")

options

Conan packages recipes can generate different binary packages when different settings are used, but can also customize, per-package any other configuration that will produce a different binary.

A typical option would be being shared or static for a certain library. Note that this is optional, different packages can have this option, or not (like header-only packages), and different packages can have different values for this option, as opposed to settings, which typically have the same values for all packages being installed (though this can be controlled too, defining different settings for specific packages)

Options are defined in package recipes as dictionaries of name and allowed values:

class MyPkg(ConanFile):
    ...
    options = {"shared": [True, False]}

Options are defined as a python dictionary inside the ConanFile where each key must be a string with the identifier of the option and the value be a list with all the possible option values:

class MyPkg(ConanFile):
    ...
    options = {"shared": [True, False],
               "option1": ["value1", "value2"],}

Values for each option can be typed or plain strings, and there is a special value, ANY, for options that can take any value.

The attribute default_options has the purpose of defining the default values for the options if the consumer (consuming recipe, project, profile or the user through the command line) does not define them. It is worth noticing that an uninitialized option will get the value None and it will be a valid value if its contained in the list of valid values. This attribute should be defined as a python dictionary too, although other definitions could be valid for legacy reasons.

class MyPkg(ConanFile):
    ...
    options = {"shared": [True, False],
               "option1": ["value1", "value2"],
               "option2": "ANY"}
    default_options = {"shared": True,
                       "option1": "value1",
                       "option2": 42}

    def build(self):
        shared = "-DBUILD_SHARED_LIBS=ON" if self.options.shared else ""
        cmake = CMake(self)
        self.run("cmake . %s %s" % (cmake.command_line, shared))
        ...

Tip

• You can inspect available package options reading the package recipe, which can be done with the command conan inspect MyPkg/0.1@user/channel.

• Options "shared": [True, False] and "fPIC": [True, False] are automatically managed in CMake and AutoToolsBuildEnvironment (configure/make) build helpers.

As we mentioned before, values for options in a recipe can be defined using different ways, let’s go over all of them for the example recipe MyPkg defined above:

• Using the attribute default_options in the recipe itself.

• In the default_options of a recipe that requires this one: the values defined here will override the default ones in the recipe.

  class OtherPkg(ConanFile):
      requires = "MyPkg/0.1@user/channel"
      default_options = {"MyPkg:shared": False}
  

  Of course, this will work in the same way working with a conanfile.txt:

  [requires]
  MyPkg/0.1@user/channel
  
  [options]
  MyPkg:shared=False
  

• It is also possible to define default values for the options of a recipe using profiles. They will apply whenever that recipe is used:

  # file "myprofile"
  # use it as $ conan install -pr=myprofile
  [settings]
  setting=value
  
  [options]
  MyPkg:shared=False
  

• Last way of defining values for options, with the highest priority over them all, is to pass these values using the command argument -o in the command line:

  $ conan install . -o MyPkg:shared=True -o OtherPkg:option=value
  

Values for options can be also conditionally assigned (or even deleted) in the methods configure() and config_options(), the corresponding section has examples documenting these use cases. However, conditionally assigning values to options can have it drawbacks as it is explained in the mastering section.

One important notice is how these options values are evaluated and how the different conditionals that we can implement in Python will behave. As seen before, values for options can be defined in Python code (assigning a dictionary to default_options) or through strings (using a conanfile.txt, a profile file, or through the command line). In order to provide a consistent implementation take into account these considerations:

• Evaluation for the typed value and the string one is the same, so all these inputs would behave the same:

  • default_options = {"shared": True, "option": None}

  • default_options = {"shared": "True", "option": "None"}

  • MyPkg:shared=True, MyPkg:option=None on profiles, command line or conanfile.txt

• Implicit conversion to boolean is case insensitive, so the expression bool(self.options.option):

  • equals True for the values True, "True" and "true", and any other value that would be evaluated the same way in Python code.

  • equals False for the values False, "False" and "false", also for the empty string and for 0 and "0" as expected.

• Comparison using is is always equals to False because the types would be different as the option value is encapsulated inside a Conan class.

• Explicit comparisons with the == symbol are case sensitive, so:

  • self.options.option = "False" satisfies assert self.options.option == False, assert self.options.option == "False", but assert self.options.option != "false".

• A different behavior has self.options.option = None, because assert self.options.option != None.

default_options

As you have seen in the examples above, recipe’s default options are declared as a dictionary with the initial desired value of the options. However, you can also specify default option values of the required dependencies:

class OtherPkg(ConanFile):
    requires = "Pkg/0.1@user/channel"
    default_options = {"Pkg:pkg_option": "value"}

And it also works with default option values of conditional required dependencies:

class OtherPkg(ConanFile):
    default_options = {"Pkg:pkg_option": "value"}

    def requirements(self):
        if self.settings.os != "Windows":
            self.requires("Pkg/0.1@user/channel")

For this example running in Windows, the default_options for the Pkg/0.1@user/channel will be ignored, they will only be used on every other OS.

You can also set the options conditionally to a final value with config_options() instead of using default_options:

class OtherPkg(ConanFile):
    settings = "os", "arch", "compiler", "build_type"
    options = {"some_option": [True, False]}
    # Do NOT declare 'default_options', use 'config_options()'

    def config_options(self):
        if self.options.some_option == None:
            if self.settings.os == 'Android':
                self.options.some_option = True
            else:
                self.options.some_option = False

Important

Setting options conditionally without a default value works only to define a default value if not defined in command line. However, doing it this way will assign a final value to the option and not an initial one, so those option values will not be overridable from downstream dependent packages.

Important

Default options can be specified as a dictionary only for Conan version >= 1.8.

See also

Read more about the config_options() method.

requires

Specify package dependencies as a list of other packages:

class MyLibConan(ConanFile):
    requires = "Hello/1.0@user/stable", "OtherLib/2.1@otheruser/testing"

You can specify further information about the package requirements:

class MyLibConan(ConanFile):
    requires = (("Hello/0.1@user/testing"),
                ("Say/0.2@dummy/stable", "override"),
                ("Bye/2.1@coder/beta", "private"))

Requirements can be complemented by 2 different parameters:

private: a dependency can be declared as private if it is going to be fully embedded and hidden from consumers of the package. Typical examples could be a header only library which is not exposed through the public interface of the package, or the linking of a static library inside a dynamic one, in which the functionality or the objects of the linked static library are not exposed through the public interface of the dynamic library.

override: packages can define overrides of their dependencies, if they require the definition of specific versions of the upstream required libraries, but not necessarily direct dependencies. For example, a package can depend on A(v1.0), which in turn could conditionally depend on Zlib(v2), depending on whether the compression is enabled or not. Now, if you want to force the usage of Zlib(v3) you can:

class HelloConan(ConanFile):
    requires = ("A/1.0@user/stable", ("Zlib/3.0@other/beta", "override"))

This will not introduce a new dependency, it will just change Zlib v2 to v3 if A actually requires it. Otherwise Zlib will not be a dependency of your package.

version ranges

The syntax is using brackets:

class HelloConan(ConanFile):
    requires = "Pkg/[>1.0 <1.8]@user/stable"

Expressions are those defined and implemented by [python node-semver](https://pypi.org/project/node-semver/). Accepted expressions would be:

>1.1 <2.1    # In such range
2.8          # equivalent to =2.8
~=3.0        # compatible, according to semver
>1.1 || 0.8  # conditions can be OR'ed

Go to Mastering/Version Ranges if you want to learn more about version ranges.

build_requires

Build requirements are requirements that are only installed and used when the package is built from sources. If there is an existing pre-compiled binary, then the build requirements for this package will not be retrieved.

They can be specified as a comma separated tuple in the package recipe:

class MyPkg(ConanFile):
    build_requires = "ToolA/0.2@user/testing", "ToolB/0.2@user/testing"

Read more: Build requirements

exports

If a package recipe conanfile.py requires other external files, like other python files that it is importing (python importing), or maybe some text file with data it is reading, those files must be exported with the exports field, so they are stored together, side by side with the conanfile.py recipe.

The exports field can be one single pattern, like exports="*", or several inclusion patterns. For example, if we have some python code that we want the recipe to use in a helpers.py file, and have some text file, info.txt, we want to read and display during the recipe evaluation we would do something like:

exports = "helpers.py", "info.txt"

Exclude patterns are also possible, with the ! prefix:

exports = "*.py", "!*tmp.py"

This is an optional attribute, only to be used if the package recipe requires these other files for evaluation of the recipe.

exports_sources

There are 2 ways of getting source code to build a package. Using the source() recipe method and using the exports_sources field. With exports_sources you specify which sources are required, and they will be exported together with the conanfile.py, copying them from your folder to the local conan cache. Using exports_sources the package recipe can be self-contained, containing the source code like in a snapshot, and then not requiring downloading or retrieving the source code from other origins (git, download) with the source() method when it is necessary to build from sources.

The exports_sources field can be one single pattern, like exports_sources="*", or several inclusion patterns. For example, if we have the source code inside “include” and “src” folders, and there are other folders that are not necessary for the package recipe, we could do:

exports_sources = "include*", "src*"

Exclude patterns are also possible, with the ! prefix:

exports_sources = "include*", "src*", "!src/build/*"

This is an optional attribute, used typically when source() is not specified. The main difference with exports is that exports files are always retrieved (even if pre-compiled packages exist), while exports_sources files are only retrieved when it is necessary to build a package from sources.

generators

Generators specify which is the output of the install command in your project folder. By default, a conanbuildinfo.txt file is generated, but you can specify different generators and even use more than one.

class MyLibConan(ConanFile):
    generators = "cmake", "gcc"

Check the full generators list.

should_configure, should_build, should_install, should_test

Read only variables defaulted to True.

These variables allow you to control the build stages of a recipe during a conan build command with the optional arguments --configure/--build/--install/--test. For example, consider this build() method:

def build(self):
    cmake = CMake(self)
    cmake.configure()
    cmake.build()
    cmake.install()
    cmake.test()

If nothing is specified, all four methods will be called. But using command line arguments, this can be changed:

$ conan build . --configure  # only run cmake.configure(). Other methods will do nothing
$ conan build . --build      # only run cmake.build(). Other methods will do nothing
$ conan build . --install    # only run cmake.install(). Other methods will do nothing
$ conan build . --test       # only run cmake.test(). Other methods will do nothing
# They can be combined
$ conan build . -c -b # run cmake.configure() + cmake.build(), but not cmake.install() nor cmake.test()

Autotools and Meson helpers already implement the same functionality. For other build systems, you can use these variables in the build() method:

def build(self):
    if self.should_configure:
        # Run my configure stage
    if self.should_build:
        # Run my build stage
    if self.should_install: # If my build has install, otherwise use package()
        # Run my install stage
    if self.should_test:
        # Run my test stage

Note that the should_configure, should_build, should_install, should_test variables will always be True while building in the cache and can be only modified for the local flow with conan build.

build_policy

With the build_policy attribute the package creator can change the default conan’s build behavior. The allowed build_policy values are:

• missing: If no binary package is found, Conan will build it without the need to invoke conan install --build missing option.

• always: The package will be built always, retrieving each time the source code executing the “source” method.

 class PocoTimerConan(ConanFile):
     build_policy = "always" # "missing"

short_paths

This attribute is specific to Windows, and ignored on other operating systems. It tells Conan to workaround the limitation of 260 chars in Windows paths.

Important

Since Windows 10 (ver. 10.0.14393), it is possible to enable long paths at the system level. Latest python 2.x and 3.x installers enable this by default. With the path limit removed both on the OS and on Python, the short_paths functionality becomes unnecessary, and may be disabled explicitly through the CONAN_USER_HOME_SHORT environment variable.

Enabling short paths management will “link” the source and build directories of the package to the drive root, something like C:\.conan\tmpdir. All the folder layout in the local cache is maintained.

Set short_paths=True in your conanfile.py:

from conans import ConanFile

class ConanFileTest(ConanFile):
    ...
    short_paths = True

See also

There is an environment variable CONAN_USE_ALWAYS_SHORT_PATHS to globally enable this behavior for all packages.

no_copy_source

The attribute no_copy_source tells the recipe that the source code will not be copied from the source folder to the build folder. This is mostly an optimization for packages with large source codebases, to avoid extra copies. It is mandatory that the source code must not be modified at all by the configure or build scripts, as the source code will be shared among all builds.

To be able to use it, the package recipe can access the self.source_folder attribute, which will point to the build folder when no_copy_source=False or not defined, and will point to the source folder when no_copy_source=True

When this attribute is set to True, the package() method will be called twice, one copying from the source folder and the other copying from the build folder.

source_folder

The folder in which the source code lives.

When a package is built in the Conan local cache its value is the same as the build folder by default. This is due to the fact that the source code is copied from the source folder to the build folder to ensure isolation and avoiding modifications of shared common source code among builds for different configurations. Only when no_copy_source=True this folder will actually point to the package source folder in the local cache.

When executing Conan commands in the Package development flow like conan source, this attribute will be pointing to the folder specified in the command line.

install_folder

The folder in which the installation of packages outputs the generator files with the information of dependencies. By default in the the local cache its value is the same as self.build_folder one.

When executing Conan commands in the Package development flow like conan install or conan build, this attribute will be pointing to the folder specified in the command line.

build_folder

The folder used to build the source code. In the local cache a build folder is created with the name of the package ID that will be built.

When executing Conan commands in the Package development flow like conan build, this attribute will be pointing to the folder specified in the command line.

package_folder

The folder to copy the final artifacts for the binary package. In the local cache a package folder is created for every different package ID.

When executing Conan commands in the Package development flow like conan package, this attribute will be pointing to the folder specified in the command line.

cpp_info

Important

This attribute is only defined inside package_info() method being None elsewhere.

The self.cpp_info is responsible for storing all the information needed by consumers of a package: include directories, library names, library paths… There are some default values that will be applied automatically if not indicated otherwise.

This object should be filled in package_info() method.

NAME	DESCRIPTION
self.cpp_info.includedirs	Ordered list with include paths. Defaulted to ["include"]
self.cpp_info.libdirs	Ordered list with lib paths. Defaulted to ["lib"]
self.cpp_info.resdirs	Ordered list of resource (data) paths. Defaulted to ["res"]
self.cpp_info.bindirs	Ordered list with include paths. Defaulted to ["bin"]
self.cpp_info.builddirs	Ordered list with build scripts directory paths. Defaulted to [""] (Package folder directory) CMake generators will search in these dirs for files like findXXX.cmake
self.cpp_info.libs	Ordered list with the library names, Defaulted to [] (empty)
self.cpp_info.defines	Preprocessor definitions. Defaulted to [] (empty)
self.cpp_info.cflags	Ordered list with pure C flags. Defaulted to [] (empty)
self.cpp_info.cppflags	Ordered list with C++ flags. Defaulted to [] (empty)
self.cpp_info.sharedlinkflags	Ordered list with linker flags (shared libs). Defaulted to [] (empty)
self.cpp_info.exelinkflags	Ordered list with linker flags (executables). Defaulted to [] (empty)
self.cpp_info.rootpath	Filled with the root directory of the package, see deps_cpp_info

The paths of the directories in the directory variables indicated above are relative to the self.package_folder directory.

See also

Read package_info() for more info.

deps_cpp_info

Contains the cpp_info object of the requirements of the recipe. In addition of the above fields, there are also properties to obtain the absolute paths:

NAME	DESCRIPTION
self.cpp_info.include_paths	Same as includedirs but transformed to absolute paths
self.cpp_info.lib_paths	Same as libdirs but transformed to absolute paths
self.cpp_info.bin_paths	Same as bindirs but transformed to absolute paths
self.cpp_info.build_paths	Same as builddirs but transformed to absolute paths
self.cpp_info.res_paths	Same as resdirs but transformed to absolute paths

To get a list of all the dependency names from `deps_cpp_info`, you can call the deps member:

class PocoTimerConan(ConanFile):
    ...
    def build(self):
        # deps is a list of package names: ["Poco", "zlib", "OpenSSL"]
        deps = self.deps_cpp_info.deps

It can be used to get information about the dependencies, like used compilation flags or the root folder of the package:

 class PocoTimerConan(ConanFile):
     ...
     requires = "zlib/1.2.11@conan/stable", "OpenSSL/1.0.2l@conan/stable"
     ...

     def build(self):
         # Get the directory where zlib package is installed
         self.deps_cpp_info["zlib"].rootpath

         # Get the absolute paths to zlib include directories (list)
         self.deps_cpp_info["zlib"].include_paths

         # Get the sharedlinkflags property from OpenSSL package
         self.deps_cpp_info["OpenSSL"].sharedlinkflags

env_info

This attribute is only defined inside package_info() method, being None elsewhere, so please use it only inside this method.

The self.env_info object can be filled with the environment variables to be declared in the packages reusing the recipe.

See also

Read package_info() method docs for more info.

deps_env_info

You can access to the declared environment variables of the requirements of the recipe.

Note: The environment variables declared in the requirements of a recipe are automatically applied and it can be accessed with the python os.environ dictionary. Nevertheless if you want to access to the variable declared by some specific requirement you can use the self.deps_env_info object.

 import os

 class RecipeConan(ConanFile):
     ...
     requires = "package1/1.0@conan/stable", "package2/1.2@conan/stable"
     ...

     def build(self):
         # Get the SOMEVAR environment variable declared in the "package1"
         self.deps_env_info["package1"].SOMEVAR

         # Access to the environment variables globally
         os.environ["SOMEVAR"]

user_info

This attribute is only defined inside package_info() method, being None elsewhere, so please use it only inside this method.

The self.user_info object can be filled with any custom variable to be accessed in the packages reusing the recipe.

See also

Read package_info() method docs for more info.

deps_user_info

You can access the declared user_info.XXX variables of the requirements through the self.deps_user_info object like this:

 import os

 class RecipeConan(ConanFile):
     ...
     requires = "package1/1.0@conan/stable"
     ...

     def build(self):
         self.deps_user_info["package1"].SOMEVAR

info

Object used to control the unique ID for a package. Check the package_id() to see the details of the self.info object.

apply_env

When True (Default), the values from self.deps_env_info (corresponding to the declared env_info in the requires and build_requires) will be automatically applied to the os.environ.

Disable it setting apply_env to False if you want to control by yourself the environment variables applied to your recipes.

You can apply manually the environment variables from the requires and build_requires:

 import os
 from conans import tools

 class RecipeConan(ConanFile):
     apply_env = False

     def build(self):
         with tools.environment_append(self.env):
             # The same if we specified apply_env = True
             pass

in_local_cache

A boolean attribute useful for conditional logic to apply in user folders local commands. It will return True if the conanfile resides in the local cache ( we are installing the package) and False if we are running the conanfile in a user folder (local Conan commands).

import os

class RecipeConan(ConanFile):
    ...

    def build(self):
        if self.in_local_cache:
            # we are installing the package
        else:
            # we are building the package in a local directory

develop

A boolean attribute useful for conditional logic. It will be True if the package is created with conan create, or if the conanfile.py is in user space:

class RecipeConan(ConanFile):

    def build(self):
        if self.develop:
            self.output.info("Develop mode")

It can be used for conditional logic in other methods too, like requirements(), package(), etc.

This recipe will output “Develop mode” if:

$ conan create . user/testing
# or
$ mkdir build && cd build && conan install ..
$ conan build ..

But it will not output that when it is a transitive requirement or installed with conan install.

keep_imports

Just before the build() method is executed, if the conanfile has an imports() method, it is executed into the build folder, to copy binaries from dependencies that might be necessary for the build() method to work. After the method finishes, those copied (imported) files are removed, so they are not later unnecessarily repackaged.

This behavior can be avoided declaring the keep_imports=True attribute. This can be useful, for example to repackage artifacts

scm

Warning

This is an experimental feature subject to breaking changes in future releases.

Used to clone/checkout a repository. It is a dictionary with the following possible values:

from conans import ConanFile, CMake, tools

class HelloConan(ConanFile):
     scm = {
        "type": "git",
        "subfolder": "hello",
        "url": "https://github.com/memsharded/hello.git",
        "revision": "static_shared"
     }
    ...

• type (Required): Currently only git and svn are supported. Others can be added eventually.

• url (Required): URL of the remote or auto to capture the remote from the local working copy (credentials will be removed from it). When type is svn it can contain the peg_revision.

• revision (Required): id of the revision or auto to capture the current working copy one. When type is git, it can also be the branch name or a tag.

• subfolder (Optional, Defaulted to .): A subfolder where the repository will be cloned.

• username (Optional, Defaulted to None): When present, it will be used as the login to authenticate with the remote.

• password (Optional, Defaulted to None): When present, it will be used as the password to authenticate with the remote.

• verify_ssl (Optional, Defaulted to True): Verify SSL certificate of the specified url.

• submodule (Optional, Defaulted to None):

  • shallow: Will sync the git submodules using submodule sync

  • recursive: Will sync the git submodules using submodule sync --recursive

SCM attributes are evaluated in the workspace context where the conanfile.py is located before exporting it to the Conan cache, so these values can be returned from arbitrary functions that depend on the workspace layout. Nevertheless, all the other code in the recipe must be able to run in the export folder inside the cache, where it has access only to the files exported (see attribute exports) and to any other functionality from a python_requires.

To know more about the usage of scm check:

• Creating packages/Recipe and sources in a different repo

• Creating packages/Recipe and sources in the same repo