No direct command can be use to read a script file and execute it. But the isql.exe and osql.exe come in handy when you have to execute a script file from within T-SQL. Just call any of these exes using xp_cmdshell and pass the script file name as parameter to it. See SQL Server Books Online for more information about the input parameters of these exes. Here are some quick examples:
EXEC master..xp_cmdshell 'osql /d DatabaseName /U UserName /P Password /i C:\YourFileNameWithExt -n'
See xp_cmdshell in SQL Server Books Online if you are having permissions problems in getting this technique to work
Hope this will work.