shell同时执行在多个linux上

#!/bin/bash                                            
if [ "$#" -ne 2 ] ; then                               
    echo "USAGE: $0 -f server_list_file cmd"           
    exit -1                                            
fi                                                     
                                                       
file_name=$1                                           
cmd_str=$2                                             
                                                       
cwd=$(pwd)                                             
cd $cwd                                                
serverlist_file="$cwd/$file_name"                      
                                                       
if [ ! -e $serverlist_file ] ; then                    
    echo ‘server.list not exist‘;                      
    exit 0                                             
fi                                                     
                                                       
while read line                                        
do                                                     
    #echo $line                                        
    if [ -n "$line" ] ; then     
        echo "DOING--->>>>>" $line "<<<<<<<"
        ssh $line $cmd_str < /dev/null > /dev/null                                                                                                         
        if [ $? -eq 0 ] ; then                         
            echo "$cmd_str done!"                      
        else                                           
            echo "error: " $?                          
        fi                                             
    fi                                                 
done < $serverlist_file