Though it may be cleaner long-term to implement system() to pass
individual arguments, rather than passing a single string which will
have to be re-processed by the shell. So the API would end up like:
UPDATE result SET nRows = system('wc', '-l', fileNames);
The reason I suggest this is because [fileNames] could have spaces
which would have to be escaped, but there are probably a dozen other
similar issues which are likely to come up.
[Though, yes, this means you'll have to use fork() and execlp() and
waitpid() to implement, rather than popen(). There are examples out
there of how to do that:
https://www.securecoding.cert.org/confluence/pages/viewpage.action?pageId=2130132
]
-scott
On Wed, Jan 11, 2017 at 1:38 PM, Roman Fleysher
<roman.fleys...@einstein.yu.edu> wrote:
> Yes, Richard, this is exactly what I mean.
>
> Roman
> ________________________________________
> From: sqlite-users [sqlite-users-boun...@mailinglists.sqlite.org] on behalf
> of Richard Hipp [d...@sqlite.org]
> Sent: Wednesday, January 11, 2017 4:34 PM
> To: SQLite mailing list
> Subject: Re: [sqlite] extension to run bash
>
> On 1/11/17, Roman Fleysher <roman.fleys...@einstein.yu.edu> wrote:
>> Dear SQLites,
>>
>> I am using exclusively sqlite3 shell for all the processing and may need
>> ability to run bash commands and assign result to a column. For example:
>>
>> UPDATE result SET nRows =` wc -l fileNames` ;
>>
>> Here I used `` as would be in bash for command substitution. This would run
>> wc command (word count), count number of lines in each file listed in column
>> fileNames and update the row correspondingly.
>>
>> As far as I understand I should be able to write loadable extension to
>> accomplish this.
>
> No, You cannot do exactly what you describe with a loadable extension.
>
> But you could, perhaps, create a loadable extension that implements a
> new system() SQL function like this:
>
> UPDATE result SET nRows = system('wc -l ' || fileNames);
>
> Note that || is the SQL string concatenation operator. You didn't
> say, but I'm guessing that fileNames is a column in the result table.
> --
> D. Richard Hipp
> d...@sqlite.org
> _______________________________________________
> sqlite-users mailing list
> sqlite-users@mailinglists.sqlite.org
> http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
> _______________________________________________
> sqlite-users mailing list
> sqlite-users@mailinglists.sqlite.org
> http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
_______________________________________________
sqlite-users mailing list
sqlite-users@mailinglists.sqlite.org
http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
