Shell脚本解读——docker官方镜像Mysql构建脚本

docker官方镜像Mysql构建脚本

概述

解读官方脚本，为了模仿官方格式，提升自己的Shell脚本的编写能力和规范编写方式。如下是原版脚本内容：

#!/bin/bash

set -eo pipefail  
shopt -s nullglob 

mysql_log() {
        local type="$1"; shift
        printf '%s [%s] [Entrypoint]: %s
' "$(date --rfc-3339=seconds)" "$type" "$*"
}
mysql_note() {
        mysql_log Note "$@"
}
mysql_warn() {
        mysql_log Warn "$@" >&2
}
mysql_error() {
        mysql_log ERROR "$@" >&2
        exit 1
}

# usage: file_env VAR [DEFAULT]
#    ie: file_env 'XYZ_DB_PASSWORD' 'example'
# (will allow for "$XYZ_DB_PASSWORD_FILE" to fill in the value of
#  "$XYZ_DB_PASSWORD" from a file, especially for Docker's secrets feature)
file_env() {
        local var="$1"
        local fileVar="${var}_FILE"
        local def="${2:-}"
        if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
                mysql_error "Both $var and $fileVar are set (but are exclusive)"
        fi
        local val="$def"
        if [ "${!var:-}" ]; then
                val="${!var}"
        elif [ "${!fileVar:-}" ]; then
                val="$(< "${!fileVar}")"
        fi
        export "$var"="$val"
        unset "$fileVar"
}

# check to see if this file is being run or sourced from another script
_is_sourced() {
        # https://unix.stackexchange.com/a/215279
        [ "${#FUNCNAME[@]}" -ge 2 ] 
                && [ "${FUNCNAME[0]}" = '_is_sourced' ] 
                && [ "${FUNCNAME[1]}" = 'source' ]
}

# usage: docker_process_init_files [file [file [...]]]
#    ie: docker_process_init_files /always-initdb.d/*
# process initializer files, based on file extensions
docker_process_init_files() {
        # mysql here for backwards compatibility "${mysql[@]}"
        mysql=( docker_process_sql )

        echo
        local f
        for f; do
                case "$f" in
                        *.sh)
                                # https://github.com/docker-library/postgres/issues/450#issuecomment-393167936
                                # https://github.com/docker-library/postgres/pull/452
                                if [ -x "$f" ]; then
                                        mysql_note "$0: running $f"
                                        "$f"
                                else
                                        mysql_note "$0: sourcing $f"
                                        . "$f"
                                fi
                                ;;
                        *.sql)    mysql_note "$0: running $f"; docker_process_sql < "$f"; echo ;;
                        *.sql.gz) mysql_note "$0: running $f"; gunzip -c "$f" | docker_process_sql; echo ;;
                        *.sql.xz) mysql_note "$0: running $f"; xzcat "$f" | docker_process_sql; echo ;;
                        *)        mysql_warn "$0: ignoring $f" ;;
                esac
                echo
        done
}

mysql_check_config() {
        local toRun=( "$@" --verbose --help ) errors
        if ! errors="$("${toRun[@]}" 2>&1 >/dev/null)"; then
                mysql_error $'mysqld failed while attempting to check config
	command was: '"${toRun[*]}"$'
	'"$errors"
        fi
}

# Fetch value from server config
# We use mysqld --verbose --help instead of my_print_defaults because the
# latter only show values present in config files, and not server defaults
mysql_get_config() {
        local conf="$1"; shift
        "$@" --verbose --help --log-bin-index="$(mktemp -u)" 2>/dev/null 
                | awk -v conf="$conf" '$1 == conf && /^[^ 	]/ { sub(/^[^ 	]+[ 	]+/, ""); print; exit }'
        # match "datadir      /some/path with/spaces in/it here" but not "--xyz=abc
     datadir (xyz)"
}

# Do a temporary startup of the MySQL server, for init purposes
docker_temp_server_start() {
        if [ "${MYSQL_MAJOR}" = '5.6' ] || [ "${MYSQL_MAJOR}" = '5.7' ]; then
                "$@" --skip-networking --socket="${SOCKET}" &
                mysql_note "Waiting for server startup"
                local i
                for i in {30..0}; do
                        # only use the root password if the database has already been initializaed
                        # so that it won't try to fill in a password file when it hasn't been set yet
                        extraArgs=()
                        if [ -z "$DATABASE_ALREADY_EXISTS" ]; then
                                extraArgs+=( '--dont-use-mysql-root-password' )
                        fi
                        if docker_process_sql "${extraArgs[@]}" --database=mysql <<<'SELECT 1' &> /dev/null; then
                                break
                        fi
                        sleep 1
                done
                if [ "$i" = 0 ]; then
                        mysql_error "Unable to start server."
                fi
        else
                # For 5.7+ the server is ready for use as soon as startup command unblocks
                if ! "$@" --daemonize --skip-networking --socket="${SOCKET}"; then
                        mysql_error "Unable to start server."
                fi
        fi
}

# Stop the server. When using a local socket file mysqladmin will block until
# the shutdown is complete.
docker_temp_server_stop() {
        if ! mysqladmin --defaults-extra-file=<( _mysql_passfile ) shutdown -uroot --socket="${SOCKET}"; then
                mysql_error "Unable to shut down server."
        fi
}

# Verify that the minimally required password settings are set for new databases.
docker_verify_minimum_env() {
        if [ -z "$MYSQL_ROOT_PASSWORD" -a -z "$MYSQL_ALLOW_EMPTY_PASSWORD" -a -z "$MYSQL_RANDOM_ROOT_PASSWORD" ]; then
                mysql_error $'Database is uninitialized and password option is not specified
	You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD'
        fi
}

# creates folders for the database
# also ensures permission for user mysql of run as root
docker_create_db_directories() {
        local user; user="$(id -u)"

        # TODO other directories that are used by default? like /var/lib/mysql-files
        # see https://github.com/docker-library/mysql/issues/562
        mkdir -p "$DATADIR"

        if [ "$user" = "0" ]; then
                # this will cause less disk access than `chown -R`
                find "$DATADIR" ! -user mysql -exec chown mysql '{}' +
        fi
}

# initializes the database directory
docker_init_database_dir() {
        mysql_note "Initializing database files"
        if [ "$MYSQL_MAJOR" = '5.6' ]; then
                mysql_install_db --datadir="$DATADIR" --rpm --keep-my-cnf "${@:2}"
        else
                "$@" --initialize-insecure
        fi
        mysql_note "Database files initialized"

        if command -v mysql_ssl_rsa_setup > /dev/null && [ ! -e "$DATADIR/server-key.pem" ]; then
                # https://github.com/mysql/mysql-server/blob/23032807537d8dd8ee4ec1c4d40f0633cd4e12f9/packaging/deb-in/extra/mysql-systemd-start#L81-L84
                mysql_note "Initializing certificates"
                mysql_ssl_rsa_setup --datadir="$DATADIR"
                mysql_note "Certificates initialized"
        fi
}

# Loads various settings that are used elsewhere in the script
# This should be called after mysql_check_config, but before any other functions
docker_setup_env() {
        # Get config
        declare -g DATADIR SOCKET
        DATADIR="$(mysql_get_config 'datadir' "$@")"
        SOCKET="$(mysql_get_config 'socket' "$@")"

        # Initialize values that might be stored in a file
        file_env 'MYSQL_ROOT_HOST' '%'
        file_env 'MYSQL_DATABASE'
        file_env 'MYSQL_USER'
        file_env 'MYSQL_PASSWORD'
        file_env 'MYSQL_ROOT_PASSWORD'

        declare -g DATABASE_ALREADY_EXISTS
        if [ -d "$DATADIR/mysql" ]; then
                DATABASE_ALREADY_EXISTS='true'
        fi
}

# Execute sql script, passed via stdin
# usage: docker_process_sql [--dont-use-mysql-root-password] [mysql-cli-args]
#    ie: docker_process_sql --database=mydb <<<'INSERT ...'
#    ie: docker_process_sql --dont-use-mysql-root-password --database=mydb  /dev/null

                        docker_init_database_dir "$@"

                        mysql_note "Starting temporary server"
                        docker_temp_server_start "$@"
                        mysql_note "Temporary server started."

                        docker_setup_db
                        docker_process_init_files /docker-entrypoint-initdb.d/*

                        mysql_expire_root_user

                        mysql_note "Stopping temporary server"
                        docker_temp_server_stop
                        mysql_note "Temporary server stopped"

                        echo
                        mysql_note "MySQL init process done. Ready for start up."
                        echo
                fi
        fi
        exec "$@"
}

# If we are sourced from elsewhere, don't perform any further actions
if ! _is_sourced; then
        _main "$@"
fi

脚本内容

定义错误捕获

#!/bin/bash

set -eo pipefail  # 包括管道符，只要出现错误，脚本中断
shopt -s nullglob # 开启nullglob，确保不会将*号错误解析

定义日志输出函数

 定义日志输出内容函数，并调用日志函数

mysql_log() {
	# 定义type为本地变量，根据 shift 来动态获取函数后面的参数 type="$1"
        local type="$1"; shift
        # 将内容通过格式化输出 $type 为等级，$*为后面的其他内容
        printf '%s [%s] [Entrypoint]: %s
' "$(date --rfc-3339=seconds)" "$type" "$*"
}
mysql_note() {
		# 将第一个参数传入mysql_log函数，并通过$@捕获所有尾部参数
        mysql_log Note "$@"
}
mysql_warn() {
        mysql_log Warn "$@" >&2
}
mysql_error() {
        mysql_log ERROR "$@" >&2
        exit 1
}

获取传入的ENV变量信息

该功能是将变量和值绑定到一起

 # file_env 'MYSQL_ROOT_HOST' '%'
 # file_env 'MYSQL_DATABASE'

file_env() {
		# 获取函数变量的第一位参数 例如：file_env 'MYSQL_DATABASE'
        local var="$1"  // 1. var=MYSQL_DATABASE

        # 将var变量拼接成fileVar变量：MYSQL_DATABASE_FILE
        local fileVar="${var}_FILE" // 2. fileVar=MYSQL_DATABASE_FILE

        # $2存在值，则赋值为def变量，没有则def为空
        local def="${2:-}" // 3. 为空
        # 判断如果${!var} 和${!fileVar},也就是MYSQL_DATABASE和MYSQL_DATABASE_FILE 不为空则进入if，mysql_error输出错误日志
        if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
                mysql_error "Both $var and $fileVar are set (but are exclusive)"  // 4. 进入if输出日志
        fi
        # 将def变量传入到局部val变量
        local val="$def"  // 5. val=''
        # 如果${!var}也就是有值则进入函数体
        if [ "${!var:-}" ]; then // var=$MYSQL_DATABASE
                val="${!var}"  // val=$MYSQL_DATABASE    
        elif [ "${!fileVar:-}" ]; then
                val="$(< "${!fileVar}")"
        fi
        # 导入环境变量
        export "$var"="$val" //也就是将MYSQL_DATABASE=xxx绑定
        # 删除$fileVar变量
        unset "$fileVar"
}

执行方式判断

# 如果是./执行则函数为假执行_main函数，如果是source则为真不执行_main
_is_sourced() {
        # https://unix.stackexchange.com/a/215279
        [ "${#FUNCNAME[@]}" -ge 2 ] 
                && [ "${FUNCNAME[0]}" = '_is_sourced' ] 
                && [ "${FUNCNAME[1]}" = 'source' ]
}
if ! _is_sourced; then
        _main "$@"
fi

$FUNCNAME —— Bash 内部环境变量，它是一个包含了当前在执行调用堆栈中的所有 Shell 函数名称的数组变量。${FUNCNAME[0]} 代表当前正在执行的 Shell 函数的名称，${FUNCNAME[1]} 则代表调用函数

 测试代码

1.sh

#!/bin/bash

_is_sourced() {
        [ "${#FUNCNAME[@]}" -ge 2 ] && [ "${FUNCNAME[0]}" = '_is_sourced' ] && [ "${FUNCNAME[1]}" = 'source' ]
 
}

wsl(){
	echo 1
}


if ! _is_sourced; then
       wsl
fi

2.sh

#!/bin/bash

source ./1.sh