protobuf原始碼下載

github上下載最新版本的protobuf原始碼zip包，並解壓縮到本地
fetch_protobuf.sh

#!/bin/bash

shell_folder=$(cd "$(dirname "$0")";pwd)
pushd $shell_folder
#如果指定的檔案/資料夾存在則刪除，刪除失敗則中止指令碼
remove_if_exist(){
    if [ $# -eq 1 ]
    then
        if [ -e $1 ]
        then
            rm $1 -fr
            if [ ! $? -eq
 
 0 ]
            then
                exit -1
            fi
        fi
        return 0
    else 
        echo invalid argument:
        echo $*
        exit -1
    fi
}
exit_on_error(){
  if [ ! $? -eq 0 ]
  then
    exit -1
  fi
}
# 如果檔案存在且checksum與$2指定的md5相等則返回 1,否則返回0
# $1 待檢查的檔案路徑
# $2 md5校驗碼
need_download
 
(){
  if [ $# -eq 2 ]
    then
      if [ -f $1 ]; then
        echo "File already exists. Checking md5..."
        os=`uname -s`
        if [ "$os" = "Linux" ]; then
          checksum=`md5sum $1 | awk '{ print $1 }'`
        elif [ "$os" = "Darwin" ]; then
          checksum=`cat $1 | md5`
        fi
 

        if [ "$checksum" = "$2" ]; then
          echo "Checksum is correct. No need to download $1."
          return 1
        else
          echo "Checksum is incorrect. Need to download again $1"                
        fi
    else
      return 0
    fi
  else 
    echo invalid argument:
    echo $*
    exit -1
  fi
}
# 從github上下載原始碼,如果本地不存在指定的zip包，或md5校驗碼不匹配則從github下載
# $1 專案名稱
# $2 版本號
# $3 zip檔案的md5
# $4 專案所有者名稱
# $5 zip包檔名字首
download_from_github(){
  if [ $# -eq 5 ]
  then
    project_folder="$1-$2"
    project_package="$project_folder.zip"
    if need_download $project_package $3
    then
      echo "(下載原始碼)downloading $1 $2 source"
      wget --no-check-certificate https://github.com/$4/$1/archive/$5$2.zip -O $project_package
      exit_on_error
    fi
    remove_if_exist $project_folder
    unzip $project_package
    exit_on_error
  else
    echo invalid argument:
    echo $*
    exit -1
  fi
}

download_from_github "protobuf" "3.3.1" "9377e414994fa6165ecb58a41cca3b40" "google" "v"

popd

protobuf編譯安裝

對下載的protobuf原始碼編譯並安裝到release/protobuf_linux_x86_64資料夾下
build_protobuf.sh

#!/bin/bash
GXX_PATH="-DCMAKE_BUILD_TYPE:STRING=RELEASE"
INSTALL_FOLDER=$(dirname $(readlink -f $0))/release/protobuf_linux_x86_64
pushd protobuf-3.3.1
echo INSTALL_FOLDER:$INSTALL_FOLDER
if [ -d build.gcc ]
then 
    rm -fr build.gcc/*
else 
    mkdir build.gcc
fi
pushd build.gcc
cmake ../cmake $GXX_PATH -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$INSTALL_FOLDER  -Dprotobuf_BUILD_TESTS=off
# 編譯並安裝protobuf到指定的資料夾
make install
popd
rm -fr build.gcc
popd

上面的指令碼中在呼叫cmake生成Makefile時定義了protobuf_BUILD_TESTS=off,這是因為protobuf的CMakeLists.txt中預設定義protobuf_BUILD_TESTS=on，
而當protobuf_BUILD_TESTS=on時，需要gmock支援(https://github.com/google/googlemock),否則cmake會報如下錯誤：

CMake Error at tests.cmake:2 (message):
Cannot find gmock directory.

gmock是google公司推出的一款開源的白盒測試工具，對於我們一般的應用來說，不需要gmock提供的功能，所以這裡可以將protobuf_BUILD_TESTS=off，避免麻煩。