Install FlowCal (macOS)

#!/bin/sh

# Install FlowCal using the `setuptools` packaging library, and install
# FlowCal's dependencies using the `pip` package manager. Both tools should
# be run using Anaconda's version of Python, whose location Anaconda adds to
# the shell PATH variable in a shell initialization script (typically .zshrc
# or .bash_profile). To complicate things, the default macOS shell changed
# from bash to zsh in macOS 10.15, Catalina. To support both defaults, look
# up the current default shell, run it as an interactive login shell (which
# runs the necessary initialization scripts), and use it to install FlowCal
# via `pip` and `setuptools`.

# Look up default shell for current user using the directory service command
# line utility (dscl).
default_shell="$(dscl . -read Users/$(whoami) UserShell \
                 | sed 's/UserShell: //')"

# Make command that changes to the FlowCal directory (i.e., the directory where
# this file is located)
if [ -n "$ZSH_VERSION" ]; then
    # Base shell (/bin/sh) is zsh, use zsh syntax for location of current file
    cd_flowcal="cd -- $(dirname "${(%):-%x}");"
else
    # Base shell is not zsh, try bash syntax for location of current file
    cd_flowcal="cd -- $(dirname "${BASH_SOURCE[0]}");"
fi

# Python commands that install FlowCal. (Commands are collected via a here
# document, which is input to a `tr` command that removes the newline
# characters.)
install_flowcal="$(tr -d '\012' <<END
python -m pip install --user -r requirements.txt --no-cache-dir;
python setup.py install;
END
)"

# Run installation commands in the default shell run as an interactive ("-i")
# login ("-l") shell with a clean environment ("env -i", so the PATH variable
# is not inherited from this shell and mangled). (Getting zsh to source
# .zshrc requires an interactive shell; getting bash to source .bash_profile
# requires a login shell.)
env -i $default_shell -i -l -c "${cd_flowcal}${install_flowcal}"