Some people suggest exporting PATH only in .bash_profile instead of in .bashrc (for Bash). The helps but does not resolve the issue of possible duplicated paths in $PATH. The right way is to check for existence of the path in the $PATH environment variable first, and add it only when it does NOT already exist in $PATH. Below is an example snippet of adding paths into the environment variable $PATH.

# set $PATH
_PATHS=(
    $(ls -d $HOME/*/bin 2> /dev/null)
    $(ls -d $HOME/.*/bin 2> /dev/null)
    $(ls -d $HOME/Library/Python/3.*/bin 2> /dev/null)
    $(ls -d /usr/local/*/bin 2> /dev/null)
    $(ls -d /opt/*/bin 2> /dev/null)
)
for ((_i=${#_PATHS[@]}-1; _i>=0; _i--)); do
    _PATH=${_PATHS[$_i]}
    if [[ -d $_PATH && ! "$PATH" =~ (^$_PATH:)|(:$_PATH:)|(:$_PATH$) ]]; then
        export PATH=$_PATH:$PATH
    fi
done

The snippet has the advatage that it works well in both .bashrc and .bash_profile. So, you can safely add such snippets into .bashrc and keep your .bash_profile as simple as the following.

if [[ -f ~/.bashrc ]]; then
    . ~/.bashrc
fi

References

• path.sh