using DOS START command inside of xp_cmdshell

  • What I want to do is to issue a START command inside the xp_cmdshell.  This should start a new cmd process with whatever command I put after the START and then continue and not wait for the cmd to finish.

    What happens is the xp_cmdshell waits for any other processes to finish before returning a finished status.

    When I manually run the same command in a cmd window, it finishes and returns control to the cmd window.  I can then close the cmd window and the subprocess continues.  Which is basically what I want to do, but inside xp_cmdshell.  The command that comes after the START command is generated at runtime.

    I have tried to put the START command inside a batch file and then run the batch file from xp_cmdshell, but I get the same results.

    I have tried to pipe the output of the START command to another file, but same results.

    Any help in this matter is greatly appreciated.


    Live to Throw
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    Will Summers

  • In the past I created a nightly process that kicked off jobs from a table schedule.

    I wanted the sproc scheduler to kick off individual threads. I solved the problem by kicking off jobs, which go off and execute on their own. I only had so many types of threads and created that many typed/generic jobs that I passed appropriate values.

    Not sure if that is a solution type you were searching for.

    daryl

  • Ok, how can I get a start a stored procedure in a script and not have the script wait for the stored procedure to finish before continuing?


    Live to Throw
    Throw to Live
    Will Summers

  • Create a job that fires each proc that needs to be ran.  Then fire all the jobs sequentially, DOS will not wait for their execution to continue (he I understand what he said!).

  • You can create a job scheduled for the next second which will delete itself after it's completed.

    _____________
    Code for TallyGenerator

  • I think I have the seeds to my solution.  Thanks. 

    I am still curious as to why the xp_cmdshell won't work with the START command in DOS.


    Live to Throw
    Throw to Live
    Will Summers

  • That's probably because of what you are trying to do within that START.

    There must be some OSQL or BCP call, right?

    _____________
    Code for TallyGenerator

  • I'm not trying to do anything special inside the START command.

    My command inside my procedure is:

    declare @CMD CHAR(100)

    SET @CMD='START DIR C:\*.* /S'

    exec master..xp_cmdshell @CMD

    START DIR C:\*.* /S takes about 1 seconds if I run it out of a command window and then another 10-20 sec for the other window to finish.

    If I run the above SQL in a query window, then it takes 10-20 seconds to run.  In my opinion, it should take 1 second to run in the query window and then the CMD window should take 10-20 seconds to end.


    Live to Throw
    Throw to Live
    Will Summers

  • Hi there,

    I had xp_cmdchell 'start bla bla bla' running well till last night. I spent hours figuring out what could be wrong. Exactly same situation as you told.

    Doesn't really matter either mentioned command is execudet by sqlagent or directly from query analyzer. I mean - different users in my case.

    But anyway, after server restart it runs again .... so , any ideas on it ?!

    Best,

    Aivars

  • Can I answer a question 11 years later?

    Its a very picky thing but I have found this will make it work.  It can be used to do a form of multi threading since the start executes without waiting.

    declare @rc as int
    declare @DynamicSQL Varchar(500)
    Set @DynamicSQL = 'cmd /c start /d c:\windows\ /B SQLCMD -U "username" -P "password" -S "server" -q " select GETDATE()" -d database -o "T:\Alerts\report.txt" '
    print @DynamicSQL
    execute @rc = XP_CMDSHELL @DynamicSQL

    I don't always test my SQL scripts, but when I do, I test in Production.

  • KTD - Wednesday, November 1, 2017 1:32 PM

    Can I answer a question 11 years later?

    Its a very picky thing but I have found this will make it work.  It can be used to do a form of multi threading since the start executes without waiting.

    declare @rc as int
    declare @DynamicSQL Varchar(500)
    Set @DynamicSQL = 'cmd /c start /d c:\windows\ /B SQLCMD -U "username" -P "password" -S "server" -q " select GETDATE()" -d database -o "T:\Alerts\report.txt" '
    print @DynamicSQL
    execute @rc = XP_CMDSHELL @DynamicSQL

    I haven't tried it but that looks right to me.  And I love it when someone answers a question even if it is 11 years old.  Seriously.  Well done.

    --Jeff Moden


    RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
    First step towards the paradigm shift of writing Set Based code:
    ________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.
    "Change is inevitable... change for the better is not".

    Helpful Links:
    How to post code problems
    How to Post Performance Problems
    Create a Tally Function (fnTally)
    Intro to Tally Tables and Functions

  • the needed parameter for START is /WAIT

    RegardsRudy KomacsarSenior Database Administrator"Ave Caesar! - Morituri te salutamus."

  • Rudyx - the Doctor - Thursday, November 2, 2017 3:32 PM

    the needed parameter for START is /WAIT

    Hey there, Rudy.  Long time no see.  Glad to see you're still around.

    I could be wrong but I'm pretty sure that /WAIT is the exact opposite of what the OP is trying to do which is to kick something off and exit from the xp_CmdShell without waiting.

    --Jeff Moden


    RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
    First step towards the paradigm shift of writing Set Based code:
    ________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.
    "Change is inevitable... change for the better is not".

    Helpful Links:
    How to post code problems
    How to Post Performance Problems
    Create a Tally Function (fnTally)
    Intro to Tally Tables and Functions

  • Hi Jeff,

    To start with Merry Christmas and Happy New Year

    I came across a situation where I have to invoke parallel sessions and that has to be done through query window with various different values for a proc in batch , after doing research, I came across this article and have started testing and based on my tests, I don't see parallel sessions open and  different sets of commands do run under each session but it runs serially.

    To test it I have tested the following piece of code.

    declare @minid tinyint =1, @maxid tinyint =10

    declare @sqlstring varchar(4000)

    declare @rc int

    while @minid <= @maxid

    begin

    Set @sqlstring = ' cmd /c start /d c:\windows\ /B SQLCMD -E -S "'+ convert(varchar(256),@@servername)+'" -i "e:\canbedeleted\test.sql" -o "e:\canbedeleted\logs\test_'+convert(varchar(3),@minid) +'.log" -d master'

    print @sqlstring

    exec @rc =master.dbo.xp_cmdshell @sqlstring

    set @minid = @minid +1

    end

     

     

    Test.sql file contains the following code.

     

    declare @miniteration tinyint =1 ,@maxiteration tinyint =3

    startprocess:

    while @miniteration <= @maxiteration

    begin

    select getdate() CollectDateTime,substring(s2.status,1,30) Status,s2.session_id,s2.start_time,s2.blocking_session_id,convert(varchar(6),s2.cpu_time) CPU,

    s2.logical_reads,s2.reads,s2.writes, s2.command,

    convert(varchar(30),DB_NAME(s2.database_id)) DBName,

    s2.percent_complete,substring(s2.wait_type,1,45) WaitType,substring(s2.last_wait_type,1,20) LastWaitResource,

    s2.wait_time,

    s2.wait_resource,

    SUBSTRING (s1.text, (s2.statement_start_offset/2)+1,

    ((CASE s2.statement_end_offset

    WHEN -1 THEN DATALENGTH(s1.text)

    ELSE s2.statement_end_offset

    END - s2.statement_start_offset)/2) + 1) AS statement_text

    ,s3.login_name,

    s3.program_name,s3.host_name -- into dbadmin.dbo.temp_capture

    from master.sys.dm_exec_requests s2

    cross apply master.sys.dm_exec_sql_text (s2.sql_handle)s1

    inner join master.sys.dm_exec_sessions s3

    on s2.session_id = s3.session_id

    waitfor delay '00:00:10'

    set @miniteration = @miniteration +1

    end

     

    I see the code is working fine, but intent of invoking parallel sessions is not happening,  just want to follow up, am I missing any thing

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