hadoop中从分布式集群下载数据hdfs下载数据的函数的操作意义和源代码分别是什么？

## 功能: 将hadoop上的文件下载到本地并merge到一个文件中
## $1 hadoop叶子目录 或 文件名--支持通配符 (*)
## $2 本地文件名
## $? return 0 if success, none-0 otherwise
function hadoop_getmerge()
{
    ## check params
    if [ $# -ne 2 ]
    then
        log_info "Unexpected params for hadoop_getmerge() function! Usage: hadoop_getmerge <hadoop_file> <local_file>";
        return 1;
    fi

    if [ -f $2 ]
    then
        log_info "Can not do hadoop_getmerge because local file $2 already exists!"
        return 2;
    fi

    ## do it
    ${HADOOP_EXEC} --config ${HADOOP_CONF} fs -getmerge $1 $2;
    if [ $? -ne 0 ]
    then
        log_info "Do hadoop_getmerge FAILED! Source: $1, target: $2";
        return 3;
    else
        log_info "Do hadoop_getmerge OK! Source: $1, target: $2";
        return 0;
    fi

    return 0;
}