build/envsetup.sh 脚本主体部分
看源代码之前需要了解代码分布和结构，分析Makefile应该是最好的方法。在Blog记录之以备以后查看，也供有兴趣朋友参考。
在编译donut之前，需要运行
cd ~/mydroid. build/envsetup.shlunch aosp_dream_us-engmake
build/envsetup.sh 是编译android的入口。该shell脚本定义了一些函数，并设定了编译的环境变量。
lunch aosp_dream_us-eng 配置用户需要编译的目标产品(target product)和变体(variant)。
aosp_dream_us-eng 字符串包含了target product 和variant，它们用减号-隔开，aosp_dream_us是target product，eng是variant。
variant 有三种选择user userdebug eng，可以从字面上看出其意义，但具体的差别还不是特别清楚，待后面分析之。
lunch 的入口是让用户指定或者选择需要编译的target product 和 variant，出口是设定编译相关的环境变量。
build/envsetup.sh 定义了很多函数，并且执行的脚本很分散，因此下面将所有的函数都删除掉了，剩余下脚本的主体，便于代码分析和走读。
该主体主要做的事情是：
1. 首先脚本设定了两个缺省的target product，一个是generic-eng，一个是simulator
2. 运行所有vendor下的 vendorsetup.sh文件，在google官方的 donut源代码中，为vendor/aosp/vendorsetup.sh，内容如下：
add_lunch_combo aosp_emulator_us-engadd_lunch_combo aosp_emulator_eu-engadd_lunch_combo aosp_dream_us-userdebugadd_lunch_combo aosp_dream_eu-userdebugadd_lunch_combo aosp_dream_us-engadd_lunch_combo aosp_dream_eu-engadd_lunch_combo aosp_sapphire_us-userdebugadd_lunch_combo aosp_sapphire_eu-userdebugadd_lunch_combo aosp_sapphire_us-engadd_lunch_combo aosp_sapphire_eu-eng
可以看出，又添加了一些 和 aosp 相关的 target product 和 variant。
下面是脚本主体，用蓝色添加了一下注释，便于阅读：
# 定义了 variant的字符范围VARIANT_CHOICES=(user userdebug eng)
# 如果是Linux环境，定义了几个和simulator相关的函数case `uname -s` in Linux) function choosesim() { echo "Build for the simulator or the device?" echo " 1. Device" echo " 2. Simulator" echo
export TARGET_SIMULATOR= local ANSWER while [ -z $TARGET_SIMULATOR ] do echo -n "Which would you like? [1] " if [ -z "$1" ] ; then read ANSWER else echo $1 ANSWER=$1 fi case $ANSWER in "") export TARGET_SIMULATOR=false ;; 1) export TARGET_SIMULATOR=false ;; Device) export TARGET_SIMULATOR=false ;; 2) export TARGET_SIMULATOR=true ;; Simulator) export TARGET_SIMULATOR=true ;; *) echo echo "I didn't understand your response. Please try again." echo ;; esac if [ -n "$1" ] ; then break fi done
set_stuff_for_environment } ;; *) function choosesim() { echo "Only device builds are supported for" `uname -s` echo " Forcing TARGET_SIMULATOR=false" echo if [ -z "$1" ] then echo -n "Press enter: " read fi
export TARGET_SIMULATOR=false set_stuff_for_environment } ;;esac
# 首先将 LUNCH_MENU_CHOICES 变量消除# Clear this variable. It will be built up again when the vendorsetup.sh# files are included at the end of this file.unset LUNCH_MENU_CHOICES
# 当前 LUNCH_MENU_CHOICES = generic-eng# add the default one hereadd_lunch_combo generic-eng
# 当前 LUNCH_MENU_CHOICES = generic-eng simulator# if we're on linux, add the simulator. There is a special case# in lunch to deal with the simulatorif [ "$(uname)" = "Linux" ] ; then add_lunch_combo simulator fi
# 这里是MAC OS的环境，不考虑case `uname -s` in Darwin) function mgrep() { find -E . -type f -iregex '.*/(Makefile|Makefile/..*|.*/.make|.*/.mak|.*/.mk)' -print0 | xargs -0 grep --color -n "$@" }
function treegrep() { find -E . -type f -iregex '.*/.(c|h|cpp|S|java|xml)' -print0 | xargs -0 grep --color -n -i "$@" }
;; *) function mgrep() { find . -regextype posix-egrep -iregex '(.*//Makefile|.*//Makefile/..*|.*/.make|.*/.mak|.*/.mk)' -type f -print0 | xargs -0 grep --color -n "$@" }
function treegrep() { find . -regextype posix-egrep -iregex '.*/.(c|h|cpp|S|java|xml)' -type f -print0 | xargs -0 grep --color -n -i "$@" }
;;esac
# 设定当前shell环境的数组下标从0开始还是1开始，并记录在 _arrayoffset# determine whether arrays are zero-based (bash) or one-based (zsh)_xarray=(a b c)if [ -z "${_xarray[${#_xarray[@]}]}" ]then _arrayoffset=1else _arrayoffset=0fiunset _xarray
# 运行所有vendor下的 vendorsetup.sh文件#存在vendor/aosp/vendorsetup.sh当前 LUNCH_MENU_CHOICES = generic-eng simulator aosp_emulator_us-eng aosp_emulator_eu-eng aosp_dream_us-userdebug aosp_dream_eu-userdebug aosp_dream_us-eng aosp_dream_eu-eng aosp_sapphire_us-userdebug aosp_sapphire_eu-userdebug aosp_sapphire_us-eng aosp_sapphire_eu-eng
# Execute the contents of any vendorsetup.sh files we can find.for f in `/bin/ls vendor/*/vendorsetup.sh vendor/*/build/vendorsetup.sh 2> /dev/null` do echo "including $f" . $fdoneunset f
