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

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

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.

> btw, I recognized that 'cmdline' library doesn't have doxygen
> documentation, which is a gap to address. Next time when someone asks
> for entry level task, we can point this one.
> 

Yep, good idea.

/Bruce