yocto-sumo源码解析（二）: oe-buildenv-internal

1 首先，脚本先对运行方式进行了检测：

if ! $(return >/dev/null 2>&1) ; then
    echo 'oe-buildenv-internal: error: this script must be sourced'
    echo ''
    echo 'Usage: . $OEROOT/scripts/oe-buildenv-internal &&'
    echo ''
    echo 'OpenEmbedded oe-buildenv-internal - an internal script that is'
    echo 'used in oe-init-build-env to initialize oe build environment'
    echo ''
    exit 2
fi

 这个目的，就是强制OEROOT/scripts/oe-buildenv-internal以“. $OEROOT/scripts/oe-buildenv-internal”的方式运行，避免以直接执行$OEROOT/scripts/oe-buildenv-internal的方式运行，也就是希望脚本执行过程中对于环境的一些改变能够在当前shell保存下来。

2 接下来需要检测OEROOT环境变量，从本系列分享的第一章，可以得知，OEROOT即为poky-sumo-19.0.0目录：

if [ -z "$OEROOT" ]; then
    echo >&2 "Error: OEROOT is not defined!"
    return 1
fi

 3 检测当前shell是否已经包含OE SDK/ADT环境变量：

if [ -z "$OE_SKIP_SDK_CHECK" ] && [ -n "$OECORE_SDK_VERSION" ]; then
    echo >&2 "Error: The OE SDK/ADT was detected as already being present in this shell environment. Please use a clean shell when sourcing this environment script."
    return 1
fi

 在缺省情况下，OE_SKIP_SDK_CHECK为空，OECORE_SDK_VERSION为空，在这里条件是不满足的，脚本将继续后面的动作。

4 检测python2版本是否为2.7以上，但不能是3.x：

py_v2_check=$(/usr/bin/env python --version 2>&1 | grep "Python 3")
if [ -n "$py_v2_check" ]; then
    echo >&2 "OpenEmbedded requires 'python' to be python v2 (>= 2.7.3), not python v3."
    echo >&2 "Please set up python v2 as your default 'python' interpreter."
    return 1
fi
unset py_v2_check

 5 继续检测python2版本，必须是2.7.3以上，这次是在语言级别上检测：

y_v27_check=$(python -c 'import sys; print sys.version_info >= (2,7,3)')
if [ "$py_v27_check" != "True" ]; then
    echo >&2 "OpenEmbedded requires 'python' to be python v2 (>= 2.7.3), not python v3."
    echo >&2 "Please upgrade your python v2."
fi
unset py_v27_check

 6 继续检测python3版本，bitbake需要python3.4以上版本：

py_v34_check=$(python3 -c 'import sys; print(sys.version_info >= (3,4,0))')
if [ "$py_v34_check" != "True" ]; then
    echo >&2 "BitBake requires Python 3.4.0 or later as 'python3'"
    return 1
fi
unset py_v34_check

 7 设置BUILDDIR以及BITBAKEDIR，参数1为空时BUILDDIR为“build”，否则BUILDDIR为参数1，参数2不为空时，BITBAKEDIR设置为参数2，参数2为空时BITBAKE指向"$OEROOT/bitbake$BBEXTRA"或者"$OEROOT/../bitbake$BBEXTRA"：

if [ -z "$BDIR" ]; then
    if [ -z "$1" ]; then
        BDIR="build"
    else
        BDIR="$1"
        if [ "$BDIR" = "/" ]; then
            echo >&2 "Error: / is not supported as a build directory."
            return 1
        fi

        # Remove any possible trailing slashes. This is used to work around
        # buggy readlink in Ubuntu 10.04 that doesn't ignore trailing slashes
        # and hence "readlink -f new_dir_to_be_created/" returns empty.
        BDIR=$(echo $BDIR | sed -re 's|/+$||')

        BDIR=$(readlink -f "$BDIR")
        if [ -z "$BDIR" ]; then
            PARENTDIR=$(dirname "$1")
            echo >&2 "Error: the directory $PARENTDIR does not exist?"
            return 1
        fi
    fi
    if [ -n "$2" ]; then
        BITBAKEDIR="$2"
    fi
fi
if [ "${BDIR#/}" != "$BDIR" ]; then
    BUILDDIR="$BDIR"
else
    BUILDDIR="$(pwd)/$BDIR"
fi
unset BDIR

if [ -z "$BITBAKEDIR" ]; then
    BITBAKEDIR="$OEROOT/bitbake$BBEXTRA"
    test -d "$BITBAKEDIR" || BITBAKEDIR="$OEROOT/../bitbake$BBEXTRA"
fi

BITBAKEDIR=$(readlink -f "$BITBAKEDIR")
BUILDDIR=$(readlink -f "$BUILDDIR")
BBPATH=$BUILDDIR

export BBPATH

if [ ! -d "$BITBAKEDIR" ]; then
    echo >&2 "Error: The bitbake directory ($BITBAKEDIR) does not exist!  Please ensure a copy of bitbake exists at this location or specify an alternative path on the command line"
    return 1
fi

 8 设置PATH，BB_ENV_EXTRAWHITE环境变量：

# Make sure our paths are at the beginning of $PATH
for newpath in "$BITBAKEDIR/bin" "$OEROOT/scripts"; do
    # Remove any existences of $newpath from $PATH
    PATH=$(echo $PATH | sed -re "s#(^|:)$newpath(:|$)#\2#g;s#^:##")

    # Add $newpath to $PATH
    PATH="$newpath:$PATH"
done
unset BITBAKEDIR newpath

# Used by the runqemu script
export BUILDDIR
export PATH

BB_ENV_EXTRAWHITE_OE="MACHINE DISTRO TCMODE TCLIBC HTTP_PROXY http_proxy \
HTTPS_PROXY https_proxy FTP_PROXY ftp_proxy FTPS_PROXY ftps_proxy ALL_PROXY \
all_proxy NO_PROXY no_proxy SSH_AGENT_PID SSH_AUTH_SOCK BB_SRCREV_POLICY \
SDKMACHINE BB_NUMBER_THREADS BB_NO_NETWORK PARALLEL_MAKE GIT_PROXY_COMMAND \
SOCKS5_PASSWD SOCKS5_USER SCREENDIR STAMPS_DIR BBPATH_EXTRA BB_SETSCENE_ENFORCE"

BB_ENV_EXTRAWHITE="$(echo $BB_ENV_EXTRAWHITE $BB_ENV_EXTRAWHITE_OE | tr ' ' '\n' | LC_ALL=C sort --unique | tr '\n' ' ')"

export BB_ENV_EXTRAWHITE 

 那么参照本系列分享第一章中对该脚本的调用：

export OEROOT
. $OEROOT/scripts/oe-buildenv-internal &&
    TEMPLATECONF="$TEMPLATECONF" $OEROOT/scripts/oe-setup-builddir || {
    unset OEROOT
    return 1
}

 脚本最后的几个重要环境变量变更为：

　　BUILDDIR： poky-sumo-19.0.0/build-arm64

　　BITBAKEDIR：

　　PATH：poky-sumo-19.0.0/scripts:poky-sumo-19.0.0/bitbake/bin:/home/totem/bin:/home/totem/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

其中$1为build-arm64，为第一章中". oe-init-build-env build-arm64"中的$1，因为$2为空，另外两个目录亦不存在，故BITBAKEDIR为空。