prepare_dirs(){

    #創建必要的目錄，此處會輸出到安裝過程中    ECHO_DEBUG "Creating necessary directories ..."

    #PKG_DIR, PKG_MISC_DIR, 前文已經定義過了，FOR循環讀取，存在跳過，如果不存在，就直接建立。    for i in ${PKG_DIR} ${PKG_MISC_DIR}    do        [ -d "${i}" ] || mkdir -p "${i}"    done}

fetch_misc(){    #進入到這個目錄，準備下載安裝文件    cd ${PKG_MISC_DIR}   

    #計算安裝總數    misc_total=$(( $(echo ${MISCLIST} | wc -w | awk '{print $1}') ))

    #定義計數器    misc_count=1

   #安裝提醒，獲取源文件中    ECHO_INFO "Fetching source tarballs ..."

   #for循環讀取標記列表，獲得下載地址，并下載到本地    for i in ${MISCLIST}; do        url="${IREDMAIL_MIRROR}/yum/misc/${i}"        ECHO_INFO "+ ${misc_count} of ${misc_total}: ${url}"        ${FETCH_CMD} "${url}"        misc_count=$((misc_count + 1))    done}

check_md5(){    cd ${_ROOTDIR}

             #判斷操作系統,如果不是FREEBSD，則輸出信息

              if [ X"${DISTRO}" != X"FREEBSD" ]; then        ECHO_INFO -n "Validate packages ..."

        #MD5值文件         md5file="/tmp/check_md5_tmp.${RANDOM}$RANDOM}"        echo -e "${MD5LIST}" > ${md5file}        cat ${PKGMISC} >> ${md5file}        if [ X"${DISTRO}" == X'OPENBSD' ]; then

                    #OPENBSD下面計算MD5的值            md5 -c ${md5file} |grep 'FAILED'

            #FREEBSD下面的狀態值            RETVAL="$?"        else            md5sum -c ${md5file} |grep 'FAILED'            RETVAL="$?"        fi        rm -f ${md5file} 2>/dev/null

        #根據執行狀態的值，返回成功和失敗的結果。        if [ X"${RETVAL}" == X"0" ]; then            echo -e "/t[ FAILED ]"            ECHO_ERROR "MD5 check failed. Script exit .../n"            exit 255        else            echo -e "/t[ OK ]"            echo 'export status_fetch_misc="DONE"' >> ${STATUS_FILE}            echo 'export status_check_md5="DONE"' >> ${STATUS_FILE}        fi    fi}

create_repo_rhel(){

    #輸出進度，到了準備YUM源的進度了。    

    ECHO_INFO "Preparing yum repositories ..."    # 備份本地源

    #LOCAL_REPO_FILE  在conf/global文件里定義的，具體代碼如下：

    #export PROG_NAME='iRedMail'

    #

    #export YUM_REPOS_DIR='/etc/yum.repos.d'
    #export LOCAL_REPO_NAME="${PROG_NAME}"
    #export LOCAL_REPO_FILE="${YUM_REPOS_DIR}/${LOCAL_REPO_NAME}.repo"

    backup_file ${LOCAL_REPO_FILE}    

    # 構建一個iredmail的本地源    cat > ${LOCAL_REPO_FILE} <<EOF[${LOCAL_REPO_NAME}]name=${LOCAL_REPO_NAME}baseurl=${IREDMAIL_MIRROR}/yum/rpms/${DISTRO_VERSION}/enabled=1gpgcheck=0EOF    # For Red Hat Enterprise linux

    #如果系統是rhel，就用它的fedor源    if [ X"${DISTRO_CODENAME}" == X'rhel' ]; then        # repo to install epel-release without GPG check.        cat > ${YUM_REPOS_DIR}/tmp_epel.repo <<EOF[tmp_epel]name=Extra Packages for Enterprise Linux ${DISTRO_VERSION} - /$basearch#baseurl=http://download.fedoraproject.org/pub/epel/${DISTRO_VERSION}//$basearchmirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-${DISTRO_VERSION}&arch=/$basearchfailovermethod=priorityenabled=1gpgcheck=0EOF    fi    eval ${install_pkg} epel-release    if [ X"${DISTRO_CODENAME}" == X'rhel' ]; then        rm -f ${YUM_REPOS_DIR}/tmp_epel.repo    fi

    #把執行進度添加到狀態文件中    echo 'export status_create_repo_rhel="DONE"' >> ${STATUS_FILE}}

check_new_iredmail(){    # Check new version and track basic information,    # Used to help iRedMail team understand which Linux/BSD distribution    # we should take more care of.    # iRedMail version number, OS distribution, release version, code name, backend.    ECHO_INFO "Checking new version of iRedMail ..."

    #官方有個檢查新版本的工具，此處會根據前面檢測的環境條件，進行相應下載

    ${FETCH_CMD} "${IREDMAIL_MIRROR}/version/check.py/iredmail_os?iredmail_version=${PROG_VERSION}&arch=${OS_ARCH}&distro=${DISTRO}&distro_version=${DISTRO_VERSION}&distro_code_name=${DISTRO_CODENAME}" &>/dev/null    UPDATE_AVAILABLE='NO'

    #if判斷，iredmail_os應該是文件，里面有檢測的結果    if ls iredmail_os* &>/dev/null; then        info="$(cat iredmail_os*)"

        #顯然如果有info信息，則是需要更新        if [ X"${info}" == X'UPDATE_AVAILABLE' ]; then            UPDATE_AVAILABLE='YES'        fi    fi    rm -f iredmail_os* &>/dev/null

    #UPDATE_AVAILABLE的值為YES時，則提示需要下在新版本     if [ X"${UPDATE_AVAILABLE}" == X'YES' ]; then        echo ''        ECHO_ERROR "Your iRedMail version (${PROG_VERSION}) is out of date, please"        ECHO_ERROR "download the latest version and try again:"        ECHO_ERROR "http://www.iredmail.org/download.html"        echo ''        exit 255    fi

    #記錄狀態到狀態文件     echo 'export status_check_new_iredmail="DONE"' >> ${STATUS_FILE}}

echo_end_msg(){    if [ X"$(basename $0)" != X'get_all.sh' ]; then        cat <<EOF********************************************************* All tasks had been finished successfully. Next step:**   # cd ..*   # bash ${PROG_NAME}.sh*********************************************************EOF    fi}