Re: [PATCH v2] app/testpmd: show output of commands read from file

[Bruce Richardson <bruce.richardson@intel.com>]

On Thu, Aug 22, 2024 at 06:14:55PM +0100, Bruce Richardson wrote:
> On Thu, Aug 22, 2024 at 05:53:27PM +0100, Ferruh Yigit wrote:
> > On 8/22/2024 11:41 AM, Bruce Richardson wrote:
> > > Testpmd supports the "--cmdline-file" parameter to read a set of initial
> > > commands from a file. However, the only indication that this has been
> > > done successfully on startup is a single-line message, no output from
> > > the commands is seen.
> > > 
> > 
> > For user I think it makes sense to see the command [1], only concern is
> > if someone parsing testpmd output may be impacted on this, although I
> > expect it should be trivial to update the relevant parsing.
> > 
> > [1]
> > Btw, I can still see the command output, I assume because command does
> > the printf itself, for example for 'show port summary 0' command:
> > - before patch:
> > ...
> > Number of available ports: 2
> > Port MAC Address       Name         Driver         Status   Link
> > 0    xx:xx:xx:xx:xx:xx xxxx:xx:xx.x aaaaaaaa       up       xxx Gbps
> > ...
> > 
> > - after patch
> > ...
> > testpmd> show port summary 0
> > Number of available ports: 2
> > Port MAC Address       Name         Driver         Status   Link
> > 0    xx:xx:xx:xx:xx:xx xxxx:xx:xx.x aaaaaaaa       up       xxx Gbps
> > ...
> > 
> > Only difference above is, after patch the command itself also printed.
> > 
> > 
> 
> That's because the function uses printf itself, which is actually wrong.
> Any output from a cmdline function should use the "cmdline_printf" call
> which outputs to the proper cmdline filehandle.
> 
> > > To improve usability here, we can use cmdline_new rather than
> > > cmdline_file_new and have the output from the various commands sent to
> > > stdout, allowing the user to see better what is happening.
> > > 
> > > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > > 
> > > ---
> > > v2: use STDOUT_FILENO in place of hard-coded "1"
> > > ---
> > >  app/test-pmd/cmdline.c | 14 +++++++++++++-
> > >  1 file changed, 13 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/app/test-pmd/cmdline.c b/app/test-pmd/cmdline.c
> > > index b7759e38a8..52e64430d9 100644
> > > --- a/app/test-pmd/cmdline.c
> > > +++ b/app/test-pmd/cmdline.c
> > > @@ -6,6 +6,7 @@
> > >  #include <ctype.h>
> > >  #include <stdarg.h>
> > >  #include <errno.h>
> > > +#include <fcntl.h>
> > >  #include <stdio.h>
> > >  #include <stdint.h>
> > >  #include <stdlib.h>
> > > @@ -13431,7 +13432,18 @@ cmdline_read_from_file(const char *filename)
> > >  {
> > >  	struct cmdline *cl;
> > >  
> > > -	cl = cmdline_file_new(main_ctx, "testpmd> ", filename);
> > > +	/* cmdline_file_new does not produce any output which is not ideal here.
> > > +	 * Much better to show output of the commands, so we open filename directly
> > > +	 * and then pass that to cmdline_new with stdout as the output path.
> > > +	 */
> > > +	int fd = open(filename, O_RDONLY);
> > > +	if (fd < 0) {
> > > +		fprintf(stderr, "Failed to open file %s: %s\n",
> > > +			filename, strerror(errno));
> > > +		return;
> > > +	}
> > > +
> > > +	cl = cmdline_new(main_ctx, "testpmd> ", fd, STDOUT_FILENO);
> > >
> > 
> > Above is almost save as 'cmdline_file_new()' function with only
> > difference that it uses '-1' for 's_out'.
> > 
> > If this usecase may be required by others, do you think does it have a
> > value to pass 's_out' to 'cmdline_file_new()' or have a new version of
> > API that accepts 's_out' as parameter?
> > 
> 
> Yes, I thought about this, and actually started implementing a new API for
> cmdline library to that. However, I decided that, given the complexity
> here, that it's not really necessary - especially as there is no clear way
> to do things. The options are:
> 
> * extend cmdline_file_new to have a flag to echo to stdout (which would be
>   the very common case here).
> * extend cmdline_file_new to take a file handle - this is more flexible,
>   but slightly less usable.
> * add a new cmdline_file_<something>_new function to echo to stdout.
> * add a new cmdline_file_<something>_new function to write to a filehandle.
> 
> I don't like breaking the cmdline API (and ABI), so I didn't want to do
> either #1 or #2, which would be the cleanest solutions. For #3 and #4,
> naming is hard, and deciding between them is even harder. Given the choice,
> I prefer #3, as I can't see #4 being very common and we always have
> cmdline_new as a fallback anyway.
> 
> Overall, though, I threw away that work, because it didn't seem worth it,
> for the sake of having the user to do an extra "open" call.
> 

And also to add:
If there is clear consensus on what the correct option for this case is,
I'm happy enough to go back and extend the cmdline library as agreed.
:-)