Android source build/envsetup.sh 及lunch 过程

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1，source build/envsetup.sh

source 是用来运行 shell 脚本的命令功能和 "." 和相同，因此也可以写作： . build/envsetup.sh

运行效果结果如下：

xxx@xxx:~/xxx/kitkat$ . build/envsetup.sh 
including device/generic/armv7-a-neon/vendorsetup.sh
including device/generic/x86/vendorsetup.sh
including device/generic/mips/vendorsetup.sh
including sdk/bash_completion/adb.bash
buddy@RD3-199:~/C_BQ_T628VX_01/kitkat-mstar-master$

那么上面的结果是如何产生的呢？运行envsetup.sh的发生了什么呢？我们自己添加的客户分支是如何加入到 lunch 的选项中去的呢？

a，关于envsetup

envsetup 为我们提供了很多的shell脚本函数，例如 envsetup 开头的第一个函数 hmm，

function hmm() {
cat <<EOF
Invoke ". build/envsetup.sh" from your shell to add the following functions to your environment:
- lunch:   lunch <product_name>-<build_variant>
- tapas:   tapas [<App1> <App2> ...] [arm|x86|mips|armv5] [eng|userdebug|user]
- croot:   Changes directory to the top of the tree.
- m:       Makes from the top of the tree.
- mm:      Builds all of the modules in the current directory, but not their dependencies.
- mmm:     Builds all of the modules in the supplied directories, but not their dependencies.
- mma:     Builds all of the modules in the current directory, and their dependencies.
- mmma:    Builds all of the modules in the supplied directories, and their dependencies.
- cgrep:   Greps on all local C/C++ files.
- jgrep:   Greps on all local Java files.
- resgrep: Greps on all local res/*.xml files.
- godir:   Go to the directory containing a file.
 
Look at the source to view more functions. The complete list is:
EOF
    T=$(gettop)    #gettop也是envsetup.sh 中定义的一个 函数，有兴趣的童鞋可以看一下具体实现
    local A
    A=""
    for i in `cat $T/build/envsetup.sh | sed -n "/^function /s/function \([a-z_]*\).*/\1/p" | sort`; do
      A="$A $i"
    done
    echo $A
}

在运行envsetup .sh以后就可以使用 hmm命令了，此时终端会输出命令帮助提示。

简单来说，envsetup.sh 给我们提供了一组自定义的 shell命令，而lunch 就是这些自定义命令中的一个。

2，lunch 命令

我们依然来看 envsetup.sh，在envsetup.sh 中可以找到 lunch 定义

function lunch()
{
    local answer
 
    if [ "$1" ] ; then  #lunch可以接受一个输入参数，例如 lunch xxx-userdebug  此时直接选择了xxx。
        answer=$1
    else    # 如果没有输入参数，则打印选择菜单，并等待选择输入
        print_lunch_menu
        echo -n "Which would you like? [aosp_arm-eng] "
        read answer
    fi
 
    local selection=
 
    if [ -z "$answer" ]  #如果answer为空
    then
        selection=aosp_arm-eng #默认选择aosp_arm-eng
    elif (echo -n $answer | grep -q -e "^[0-9][0-9]*$")
    then
        if [ $answer -le ${#LUNCH_MENU_CHOICES[@]} ]
        then
            selection=${LUNCH_MENU_CHOICES[$(($answer-1))]}
        fi
    elif (echo -n $answer | grep -q -e "^[^\-][^\-]*-[^\-][^\-]*$") #不以 ‘-’ 开头和结束
    then
        selection=$answer
    fi
 
    if [ -z "$selection" ]
    then
        echo
        echo "Invalid lunch combo: $answer"
        return 1
    fi
    #导出编译使用的环境变量 
    export TARGET_BUILD_APPS=
    #提取"-"位置以前的字符串 这里是“xxx” 
    local product=$(echo -n $selection | sed -e "s/-.*$//")
    check_product $product
    if [ $? -ne 0 ]
    then
        echo
        echo "** Don't have a product spec for: '$product'"
        echo "** Do you have the right repo manifest?"
        product=
    fi
    #提取"-"位置以后的字符串“ userdebug  ” 
    local variant=$(echo -n $selection | sed -e "s/^[^\-]*-//")  
    check_variant $variant
    if [ $? -ne 0 ]
    then
        echo
        echo "** Invalid variant: '$variant'"
        echo "** Must be one of ${VARIANT_CHOICES[@]}"
        variant=
    fi
 
    if [ -z "$product" -o -z "$variant" ]  #如果为空则返回
    then
        echo
        return 1
    fi
     
    #导出编译使用的环境变量
    export TARGET_PRODUCT=$product
    export TARGET_BUILD_VARIANT=$variant
    export TARGET_BUILD_TYPE=release
 
    echo
 
    set_stuff_for_environment
    printconfig
}

看一看其中调用的几个函数

print_lunch_menu

function print_lunch_menu()
{
    local uname=$(uname)
    echo
    echo "You're building on" $uname
    echo
    echo "Lunch menu... pick a combo:"
 
    local i=1
    local choice
    for choice in ${LUNCH_MENU_CHOICES[@]} #这里输出的就是我们看到的 lunch 命令的输出结果
    do
        echo "     $i. $choice"
        i=$(($i+1))
    done
 
    echo
}

那么 LUNCH_MENU_CHOICES 变量的数据又是从何而来呢？

# 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
#这函数就是向lunch命令添加选择项  客户分支里 vendorsetup.sh 里的那一行代码的用途就是添加lunch选择项
function add_lunch_combo()  
{
    local new_combo=$1
    local c
    for c in ${LUNCH_MENU_CHOICES[@]} ; do
        if [ "$new_combo" = "$c" ] ; then
            return
        fi
    done
    LUNCH_MENU_CHOICES=(${LUNCH_MENU_CHOICES[@]} $new_combo)
}
 
# add the default one here
add_lunch_combo aosp_arm-eng
add_lunch_combo aosp_x86-eng
add_lunch_combo aosp_mips-eng
add_lunch_combo vbox_x86-eng

我们来看看 check_product 的作用

# check to see if the supplied product is one we can build
function check_product()
{
    T=$(gettop)
    if [ ! "$T" ]; then
        echo "Couldn't locate the top of the tree.  Try setting TOP." >&2
        return
    fi
    #设置环境变量
    CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core \
        TARGET_PRODUCT=$1 \
        TARGET_BUILD_VARIANT= \
        TARGET_BUILD_TYPE= \
        TARGET_BUILD_APPS= \
        get_build_var TARGET_DEVICE > /dev/null #get_build_var 
    # hide successful answers, but allow the errors to show
}

# Get the exact value of a build variable.
function get_build_var()
{
    T=$(gettop)
    if [ ! "$T" ]; then
        echo "Couldn't locate the top of the tree.  Try setting TOP." >&2
        return
    fi
    #执行config.mk配置相关的内容，
    #进一步依次执行envsetup.mk，到product_config.mk，
    #最终获得TARGET_DEVICE变量的内容。
    CALLED_FROM_SETUP=true BUILD_SYSTEM=build/core \
      make --no-print-directory -C "$T" -f build/core/config.mk dumpvar-$1
}

check_variant 函数

#三种模式  user userdebug eng
VARIANT_CHOICES=(user userdebug eng)  
# check to see if the supplied variant is valid
function check_variant()
{
    for v in ${VARIANT_CHOICES[@]}
    do
        if [ "$v" = "$1" ]
        then
            return 0
        fi
    done
    return 1
}

以下内容待验证
#1.eng，那么其编译进去的内容包括：
· Intended for platform-level debugging
· Installs modules tagged with: eng, debug, user, and/or development
· Installs non-APK modules that have no tags specified
· Installs APKs according to the product definition files, in addition to tagged APKs
· Sets ro.secure=1
· Sets ro.debuggable=0
· Sets ro.kernel.android.checkjni=1
· adbd is enabled by default
 
#2.user,那么其编译进去的内容包括：
· Intended to be the final release
· Installs modules tagged as user
· Installs non-APK modules that have no tags specified
· Installs APKs according to the product definition files (tags are ignored for APK modules)
· Sets ro.secure=1
· Sets ro.debuggable=0
· adbd is disabled by default
 
#3.userdebug,那么其编译进去的内容包括：
the same as user, except:
· Intended for limited debugging
· Installs modules tagged with debug
· Sets ro.debuggable=1
· adbd is enabled by default

set_stuff_for_environment函数，主要设备编译相关的环境

function set_stuff_for_environment()
{
    settitle
    set_java_home
    setpaths
    set_sequence_number
# MStar Android Patch Begin
    set_ota
# MStar Android Patch End
 
    export ANDROID_BUILD_TOP=$(gettop)
}

关于lunch 命令的过程已经基本清晰，那么系统是如何找到客户分支下的 vendorsetup.sh 呢？

3，扫描系统中的vendorsetup.sh 文件

# Execute the contents of any vendorsetup.sh files we can find.
# 检测 device 目录和vendor 目录是否存在 ，并且找到 目录下的vendorsetup.sh .最多目录层次四层
for f in `test -d device && find device -maxdepth 4 -name 'vendorsetup.sh' 2> /dev/null` \
         `test -d vendor && find vendor -maxdepth 4 -name 'vendorsetup.sh' 2> /dev/null`
do
    echo "including $f"
    . $f # 找到vendorsetup.sh  并执行，
done
unset f
 
addcompletions

function addcompletions()
{
    local T dir f
 
    # Keep us from trying to run in something that isn't bash.
    if [ -z "${BASH_VERSION}" ]; then
        return
    fi
 
    # Keep us from trying to run in bash that's too old.
    if [ ${BASH_VERSINFO[0]} -lt 3 ]; then
        return
    fi
 
    dir="sdk/bash_completion"
    if [ -d ${dir} ]; then
    # 扫描 /sdk/bash_completion 目录并允许 .bash 文件 
        for f in `/bin/ls ${dir}/[a-z]*.bash 2> /dev/null`; do
            echo "including $f"
            . $f  #运行bash文件
        done
    fi
}

source ./build/envsetup.sh

lunch

命令的基本过程大致如上所说。主要初始化编译所需要的系统变量

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