Re: [PATCH] kernel-shark: Provide parsing for quotation marks in Record command line

[stephen@brennan.io]

Hi Yordan!

Thanks for the quick work on this issue :)

On Tue, Aug 27 16:14, Yordan Karadzhov (VMware) wrote:
> Shell-like parsing of quotation marks in the content of the "Command"
> field of the "Record" dialog will give more options to the users.
> For example, now we can trace
> 
>  python -c 'print("hello world")'
> 
> Suggested-by: Stephen Brennan <stephen@brennan.io>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204679
> Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
> ---
>  kernel-shark/src/KsCaptureDialog.cpp | 38 ++++++++++++++++++++++++++--
>  1 file changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel-shark/src/KsCaptureDialog.cpp b/kernel-shark/src/KsCaptureDialog.cpp
> index dc1e9b2..b3393b6 100644
> --- a/kernel-shark/src/KsCaptureDialog.cpp
> +++ b/kernel-shark/src/KsCaptureDialog.cpp
> @@ -157,7 +157,9 @@ KsCaptureControl::KsCaptureControl(QWidget *parent)
>   */
>  QStringList KsCaptureControl::getArgs()
>  {
> +	QString::SplitBehavior opt = QString::SkipEmptyParts;
>  	QStringList argv;
> +	QString cmdTmp;
>  
>  	argv << "record";
>  
> @@ -170,7 +172,36 @@ QStringList KsCaptureControl::getArgs()
>  		argv << _eventsWidget.getCheckedEvents(true);
>  
>  	argv << "-o" << outputFileName();
> -	argv << _commandLineEdit.text().split(" ");
> +
> +	cmdTmp = _commandLineEdit.text();
> +	if (!cmdTmp.contains('\'') && !cmdTmp.contains('\"')) {
> +		/* Split all command line arguments. */
> +		argv << cmdTmp.split(" ", opt);
> +	} else {
> +		int iOpenQuots, iCloseQuots, size = cmdTmp.size();
> +		int iSingleQuots = (cmdTmp.count('\'') == 2) ? cmdTmp.indexOf('\'') : size;
> +		int iDoubleQuots = (cmdTmp.count('\"') == 2) ? cmdTmp.indexOf('\"') : size;
> +
> +		if (iSingleQuots < iDoubleQuots) {
> +			iOpenQuots = iSingleQuots;
> +			iCloseQuots = cmdTmp.lastIndexOf('\'') + 1;
> +		} else if (iDoubleQuots < iSingleQuots) {
> +			iOpenQuots = iDoubleQuots;
> +			iCloseQuots = cmdTmp.lastIndexOf('\"') + 1;
> +		} else {
> +			emit print("\nERROR: Unable to parse the command.");
> +			return {};
> +		}
> +
> +		/* Split the arguments. */
> +		argv << cmdTmp.left(iOpenQuots).split(" ", opt);
> +
> +		/* Everything in between the quotation marks goes in one piece. */
> +		argv << cmdTmp.mid(iOpenQuots, iCloseQuots - iOpenQuots);
> +
> +		/* Split the rest of the arguments. */
> +		argv << cmdTmp.right(size - iCloseQuots).split(" ", opt);
> +	}

It strikes me that this explicitly supports only a single set of quotes.
This sort of behavior would be pretty surprising for people expecting shell
quote support, and for people expecting just splitting on spaces.

I looked and couldn't really find any Qt utility for properly parsing shell
quoting (similar to python's shlex module). I totally get that it's a lot
of work to implement a correct shell quoting parser.

Maybe a compromise would be to add a checkbox to the capture dialog, which
tells kernel-shark to pass the entire textbox contents, unmodified, to the
shell implementation on the system. So, my example of:

    python -c 'print("hello world")'

Would get put into the third argument of the command:

    /bin/sh -c INSERT_TEXTBOX_CONTENTS_HERE

Then you could rely on /bin/sh doing the parsing for you. The downside is
that it adds a whole new process. But you can't always get everything in
life, right?

Hope this was helpful!

Stephen