Listing Directory Contents using T-SQL

Listing Directory Contents using T-SQL

Share on Facebook0Share on Google+0Tweet about this on TwitterShare on LinkedIn0Share on Reddit0
In many cases during the development of a sophisticated SQL Server Agent job, you might need to access the file system. For example you might want to list the contents of a specific directory and based on the output to proceed to other actions folllowing a series of steps that belong to a broader logic implemented via a SQL Server Agent job.

Don’t worry, there’s nothing stopping you from performing the above operation!

For such and similar purposes you can always use the extended stored procedure xp_cmdshell.

As described in SQL Server BoL, xp_cmdshell takes as a parameter a string and passes it to a Windows command shell for execution. Any output is returned as rows of text.

xp_cmdshell, by default, is disabled within a SQL Server instance and there is a good reason for this. When this extended stored procedure is enabled, it introduces a security risk that you should be aware of. As xp_cmdshell allows executing commands on the Operating System’s level, you should be extremely careful with who has the right to execute this stored procedure. To this end, you should always use xp_cmd with caution.

OK, enough with the theory. Let’s proceed with a practical example and some T-SQL!

–You can enable xp_cmdshell using the following T-SQL statement:
exec sp_configure ‘xp_cmdshell’,1
GO
RECONFIGURE WITH override
GO

Then, if you want for example to list the contents of the directory “c:tmp” you can do so by executing the following T-SQL statement:

— You first create a temporary table for storing the contents of the directory.
CREATE TABLE #dirContents
(
contents NVARCHAR(255)
)
GO

— You then execute xp_cmdshell by using the DOS “dir” command.
— You store the output to the temporary table created earlier.
— The contents are stored as string expressions line-by-line.
— Each empty line is a NULL.
INSERT INTO #dirContents
EXEC xp_cmdshell ‘dir “c:tmp”‘;

— You can then scan the table for the output and analyze the data
— using string manipulation techniques
SELECT *
FROM #dirContents

If you want to disable xp_cmdshell, you can do so as follows:

exec sp_configure ‘xp_cmdshell’,0
GO
RECONFIGURE WITH override
GO

I hope you found the post useful!

Cheers!


Recommended eBooks on SQL Server:

Tuning SQL Server: eBook by SQL Server MVP Artemakis Artemiou
Tuning SQL Server: eBook by SQL Server MVP Artemakis Artemiou
Administering SQL Server: eBook by SQL Server MVP Artemakis Artemiou
Administering SQL Server: eBook by SQL Server MVP Artemakis Artemiou
Artemakis Artemiou
Artemakis Artemiou is a Senior SQL Server Architect, Author, Software Developer and a Microsoft Data Platform MVP. He has over 15 years of experience in the IT industry in various roles. Among other, via his initiative SQLEBooks.com, Artemakis authors and publishes eBooks on different topics on SQL Server. Artemakis currently serves as the President of the Cyprus .NET User Group (CDNUG) and the International .NET Association Country Leader for Cyprus (INETA). Additionally he is the founder of the SQLArtBits initiative that aims to provide the technical community with simple, yet powerful and high-quality SQL Server tools. Currently, the highlights of these tools are DBA Security Advisor and In-Memory OLTP Simulator. Artemakis's official website can be found at aartemiou.com. Artemakis's blogs can be found at: SQLNetHub.com and TechHowTos.com.