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Installation.md

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Installation Script

To install rez, download the source. Then from the root directory, run:

]$ python ./install.py

This installs rez to /opt/rez. See install.py -h for how to install to a different location.

Once the installation is complete, a message tells you how to run it:

SUCCESS! To activate Rez, add the following path to $PATH:
/opt/rez/bin/rez

You may also want to source the completion script (for bash):
source /opt/rez/completion/complete.sh

[[media/icons/warning.png]] Do not move the installation - re-install to a new location if you want to change the install path. If you want to install rez for multiple operating systems, perform separate installs for each of those systems.

Installation Via Pip

It is possible to install rez with pip, like so (from source root directory):

]$ pip install --target /opt/rez .

The . (dot) can also be replaced with link to the GitHub repository, e.g. choose from:

  • git+https://github.com/nerdvegas/rez.git if you have git installed
  • https://github.com/nerdvegas/rez/archive/master.zip
  • https://github.com/nerdvegas/rez/archive/master.tar.gz

[[media/icons/warning.png]] The PyPi rez is not up to date as of writing. Avoid pip install rez

The environment variables to activate rez will be slightly different:

  1. Add /opt/rez to PYTHONPATH for API e.g. python -c 'import rez
  2. Add /opt/rez/bin to PATH for CLI, e.g. rez-env

[[media/icons/warning.png]] For these pip based installs, rez command line tools are not guaranteed to work correctly inside a rez environment, i.e. rez-env then running rez-context inside sub-shell.

See Why Not Pip For Production? below. You will also be warned with the following message in the terminal:

Pip-based rez installation detected. Please be aware that rez command line
tools are not guaranteed to function correctly in this case. See
https://github.com/nerdvegas/rez/wiki/Installation#why-not-pip-for-production
for further details.

Alternatively, if you already have rez setup and have pip>=19 available, you can then install rez as a rez package by using:

]$ rez-pip --install .

Pip installation is adequate however, if all you require is the rez API, or you don't require its command line tools (rez-context, rez-search, rez-view, etc) to be available within a resolved environment.

Why Not Pip For Production?

Rez is not a normal python package. Although it can successfully be installed using standard mechanisms such as pip, this comes with a number of caveats. Specifically:

  • When within a rez environment (ie after using the rez-env command), the rez command line tools are not guaranteed to function correctly;
  • When within a rez environment, other packages' tools (that were also installed with pip) remain visible, but are not guaranteed to work.

When you enter a rez environment, the rez packages in the resolve configure that environment as they see fit. For example, it is not uncommon for a python package to append to PYTHONPATH. Environment variables such as PYTHONPATH affect the behaviour of tools, including rez itself, and this can cause it to crash or behave abnormally.

When you use the install.py script to install rez, some extra steps are taken to avoid this problem. Specifically:

  • Rez is installed into a virtualenv so that it operates standalone;
  • The rez tools are shebanged with python -E, in order to protect them from environment variables that affect python's behaviour;
  • The rez tools are stored in their own directory, so that other unrelated tools are not visible.

Due to the way standard wheel-based python installations work, it simply is not possible to perform these extra steps without using a custom installation script. Wheels do not give the opportunity to run post-installation code; neither do they provide functionality for specifying interpreter arguments to be added for any given entry point.