Environment variables

These are the environment variables used to customize conan.

Most of them can be set in the conan.conf configuration file (inside your <userhome>/.conan folder).


Defaulted to: Not defined

Used only in windows to help the tools.run_in_windows_bash() function to locate our Cygwin/MSYS2 bash. Set it with the bash executable path if it’s not in the PATH or you want to use a different one.


Conan CMake helper class is just a convenience to help to translate conan settings and options into cmake parameters, but you can easily do it yourself, or adapt it.

For some compiler configurations, as gcc it will use by default the Unix Makefiles cmake generator. Note that this is not a package settings, building it with makefiles or other build system, as Ninja, should lead to the same binary if using appropriately the same underlying compiler settings. So it doesn’t make sense to provide a setting or option for this.

So it can be set with the environment variable CONAN_CMAKE_GENERATOR. Just set its value to your desired cmake generator (as Ninja).


Defaulted to: False/0

Set it to True/1 to use dark colors in the terminal output, instead of light ones. Useful for terminal or consoles with light colors as white, so text is rendered in Blue, Black, Magenta, instead of Yellow, Cyan, White.


Defaulted to: True/1

Useful to remove colored output, set it to False/0 to remove console output colors.


Defaulted to: 9

Conan uses tgz compression for archives before uploading them to remotes. The default compression level is good and fast enough for most cases, but users with huge packages might want to change it and set CONAN_COMPRESSION_LEVEL environment variable to a lower number, which is able to get slightly bigger archives but much better compression speed.


Defaulted to: Number of available cores in your machine.

Set the number of cores that the tools.cpu_count() will return. Conan recipes can use the cpu_count() tool to build the library using more than one core.


You can override the default settings (located in your ~/.conan/profiles/default directory) with environment variables.

The XXXX is the setting name upper-case, and the YYYY (optional) is the sub-setting name.


  • Override the default compiler:
CONAN_ENV_COMPILER = "Visual Studio"
  • Override the default compiler version:
  • Override the architecture:


Defaulted to: 0

If set to 1 will log every self.run("{Some command}") command output in a file called conan_run.log. That file will be located in the current execution directory, so if we call self.run in the conanfile.py’s build method, the file will be located in the build folder.

In case we execute self.run in our source() method, the conan_run.log will be created in the source directory, but then conan will copy it to the build folder following the regular execution flow. So the conan_run.log will contain all the logs from your conanfile.py command executions.

The file can be included in the conan package (for debugging purposes) using the package method.

def package(self):
    self.copy(pattern="conan_run.log", dst="", keep_path=False)


Defaulted to: 1

If set to 0 conan won’t print the command output to the stdout. Can be used with CONAN_LOG_RUN_TO_FILE set to 1 to log only to file and not printing the output.


Defaulted to: 50

By default conan logging level is only set for critical events. If you want to show more detailed logging information, set this variable to lower values, as 10 to show debug information.


Defaulted to: Not defined

You can define the username for the authentication process using environment variables. Conan will use a variable CONAN_LOGIN_USERNAME_{REMOTE_NAME}, if the variable is not declared Conan will use the variable CONAN_LOGIN_USERNAME, if the variable is not declared either, Conan will request to the user to input a username.

These variables are useful for unattended executions like CI servers or automated tasks.

If the remote name contains “-” you have to replace it with “_” in the variable name:

For example: For a remote named “conan-center”:



Defaulted to: Not defined

Specify an alternative make program to use with:

For example:


# Or only the exe name if it is in the path



Defaulted to: Not defined

You can define the authentication password using environment variables. Conan will use a variable CONAN_PASSWORD_{REMOTE_NAME}, if the variable is not declared Conan will use the variable CONAN_PASSWORD, if the variable is not declared either, Conan will request to the user to input a password.

These variables are useful for unattended executions like CI servers or automated tasks.

If the remote name contains “-” you have to replace it with “_” in the variable name:

For example: For a remote named “conan-center”:



Defaulted to: 0

If set to 1, every self.run("{Some command}") call will log the executed command {Some command} to the output.

For example: In the conanfile.py file:

self.run("cd %s && %s ./configure" % (self.ZIP_FOLDER_NAME, env_line))

Will print to the output (stout and/or file):

> cd zlib-1.2.9 && env LIBS="" LDFLAGS=" -m64   $LDFLAGS" CFLAGS="-mstackrealign -fPIC $CFLAGS -m64  -s -DNDEBUG  " CPPFLAGS="$CPPFLAGS -m64  -s -DNDEBUG  " C_INCLUDE_PATH=$C_INCLUDE_PATH: CPLUS_INCLUDE_PATH=$CPLUS_INCLUDE_PATH: ./configure


Defaulted to: Not defined

This environment variable if defined, will make the conan cache read-only. This could prevent developers to accidentally edit some header of their dependencies while navigating code in their IDEs.

This variable can also be set in conan.conf as read_only_cache = True in the [general] section.

The packages are made read-only in two points: when a package is built from sources, and when a package is retrieved from a remote repository.

The packages are not modified for upload, so users should take that into consideration before uploading packages, as they will be read-only and that could have other side-effects.


It is not recommended to upload packages directly from developers machines with read-only mode as it could lead to insconsistencies. For better reproducibility we recommend that packages are created and uploaded by CI machines.


Defaulted to: Not defined (True/False if defined)

This environment variable (if defined) can be used in conanfile.py to enable/disable the tests for a library or application.

It can be used as a convention variable and it’s specially useful if a library has unit tests and you are doing cross building, the target binary can’t be executed in current host machine building the package.

It can be defined in your profile files at ~/.conan/profiles


or declared in command line when invoking conan install to reduce the variable scope for conan execution

$ conan install . -e CONAN_RUN_TEST=0

See how to retrieve the value with tools.get_env() and check an use case with a header only with unit tests recipe while cross building.

See example of build method in conanfile.py to enable/disable running tests with CMake:

from conans import ConanFile, CMake, tools

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

    def build(self):
        cmake = CMake(self)
        if tools.get_env("CONAN_RUN_TESTS", True):


Defaulted to: False/0

When set to True/1, the build_sln_commmand, the msvc_build_command and the MSBuild() build helper, will not call devenv command to upgrade the sln project, irrespective of the upgrade_project parameter value.


Defaulted to: enabled allowed values enabled/verify/disabled

This environment variable controls whether system packages should be installed into the system via SystemPackageTool helper, typically used in system_requirements().

See values behaviour:

  • enabled: Default value and any call to install method of SystemPackageTool helper should modify the system packages.
  • verify: Display a report of system packages to be installed and abort with exception. Useful if you don’t want to allow conan to modify your system but you want to get a report of packages to be installed.
  • disabled: Display a report of system packages that should be installed but continue the conan execution and doesn’t install any package in your system. Useful if you want to keep manual control of these dependencies, for example in your development environment.


Defaulted to: True/1

This environment variable controls whether sudo is used for installing apt, yum, etc. system packages via SystemPackageTool helper, typically used in system_requirements(). By default when the environment variable does not exist, “True” is assumed, and sudo is automatically prefixed in front of package management commands. If you set this to “False” or “0” sudo will not be prefixed in front of the comands, however installation or updates of some packages may fail due to a lack of privilege, depending on the user account Conan is running under.


Defaulted to: False/0

Activating this variable will make build folder of test_package to be created in the temporary folder of your machine.


Defaulted to: Not defined

If you want extra logging information about your conan command executions, you can enable it by setting the CONAN_TRACE_FILE environment variable. Set it with an absolute path to a file.

export CONAN_TRACE_FILE=/tmp/conan_trace.log

When the conan command is executed, some traces will be appended to the specified file. Each line contains a JSON object. The _action field contains the action type, like COMMAND for command executions, EXCEPTION for errors and REST_API_CALL for HTTP calls to a remote.

The logger will append the traces until the CONAN_TRACE_FILE variable is unset or pointed to a different file.

See also

Read more here: How to log and debug a conan execution


Environment variables commonly used in test_package conanfiles, to allow package creation for different users and channel without modifying the code. They are also the environment variables that will be checked when using self.user or self.channel in conanfile.py package recipes in user space, where a user/channel has not been assigned yet (it is assigned when exported in the local cache).

See also

Read more about it in user, channel


Defaulted to: Not defined

Allows defining a custom conan cache directory. Can be useful for concurrent builds under different users in CI, to retrieve and store per-project specific dependencies (useful for deployment, for example).


Defaulted to: Not defined

Specify the base folder to be used with the short paths feature. When not specified, the packages marked as short_paths will be stored in the C:.conan (or the current drive letter).

If set to “None”, it will disable the short_paths feature in Windows for modern Windows that enable long paths at the system level.


Please note that this only works with Python 3.6 and newer.


Defaulted to: 0

When an error is raised in a recipe or even in the conan code base, if set to 1 it will show the complete traceback to ease the debugging.


Defaulted to: Enterprise, Professional, Community, BuildTools

This envirnoment variables defines the order of preference when searching for a Visual installation product. This would affect every tool that uses tools.vs_installation_path() and will search in the order indicated.

For example:

set CONAN_VS_INSTALLATION_PREFERENCE=Enterprise, Professional, Community, BuildTools

It can also be used to fix the type of installation you want to use indicating just one product type: