Re: [RFAv3 6/6] NEWS and documentation for | (pipe) command.

[Pedro Alves <palves@redhat.com>]

On 5/4/19 5:17 PM, Philippe Waroquiers wrote:
> gdb/ChangeLog
> 	* NEWS: Mention new pipe command and new convenience variables.
> 
> gdb/doc/ChangeLog
> 	* gdb.texinfo (Shell Commands): Document pipe command.
> 	(Logging Output): Add a reference to pipe command.
> 	(Convenience Variables): Document $_shell_exitcode and
> 	$_shell_exitstatus.
> ---
>  gdb/NEWS            | 32 ++++++++++++++--------
>  gdb/doc/gdb.texinfo | 67 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 88 insertions(+), 11 deletions(-)
> 
> diff --git a/gdb/NEWS b/gdb/NEWS
> index b21b2cbb47..570718ab5c 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -16,11 +16,23 @@
>  
>  * Support for Pointer Authentication on AArch64 Linux.
>  
> -* Two new convernience functions $_cimag and $_creal that extract the
> +* Two new convenience functions $_cimag and $_creal that extract the
>    imaginary and real parts respectively from complex numbers.
>  

Please go ahead and push this bit in as an obvious fix.

> +* New built-in convenience variables $_shell_exitcode and $_shell_exitsignal
> +  provide the exitcode or exit status of the shell commands launched by
> +  GDB commands such as "shell", "pipe", "make".
> +

That "make" should be preceded by "and".

(I'll leave oxford comma or not to someone else.  :-) )

>  * New commands
>  
> +pipe [COMMAND] | SHELL_COMMAND
> +| [COMMAND] | SHELL_COMMAND
> +pipe -d SEP COMMAND SEP SHELL_COMMAND
> +| -s DEP COMMAND SEP SHELL_COMMAND

s/DEP/SEP/

> +  Executes COMMAND and sends its output to SHELL_COMMAND.
> +  With no COMMAND, repeat the last executed command
> +  and send its output to SHELL_COMMAND.
> +
>  set print max-depth
>  show print max-depth
>    Allows deeply nested structures to be simplified when printing by
> @@ -28,16 +40,6 @@ show print max-depth
>    The default max-depth is 20, but this can be set to unlimited to get
>    the old behavior back.
>  
> -* Python API
> -
> -  ** The gdb.Value type has a new method 'format_string' which returns a
> -     string representing the value.  The formatting is controlled by the
> -     optional keyword arguments: 'raw', 'pretty_arrays', 'pretty_structs',
> -     'array_indexes', 'symbols', 'unions', 'deref_refs', 'actual_objects',
> -     'static_members', 'max_elements', 'repeat_threshold', and 'format'.
> -
> -* New commands
> -
>  set may-call-functions [on|off]
>  show may-call-functions
>    This controls whether GDB will attempt to call functions in
> @@ -48,6 +50,14 @@ show may-call-functions
>    an error when a command (such as print expression) calls a function
>    in the program.
>  
> +* Python API
> +
> +  ** The gdb.Value type has a new method 'format_string' which returns a
> +     string representing the value.  The formatting is controlled by the
> +     optional keyword arguments: 'raw', 'pretty_arrays', 'pretty_structs',
> +     'array_indexes', 'symbols', 'unions', 'deref_refs', 'actual_objects',
> +     'static_members', 'max_elements', 'repeat_threshold', and 'format'.
> +

This also looks like a change that should go in separately, as
an obvious fix.

>  *** Changes in GDB 8.3
>  
>  * GDB and GDBserver now support access to additional registers on
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index dd8ae91b93..36e3f8bc35 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -1454,6 +1454,56 @@ Execute the @code{make} program with the specified
>  arguments.  This is equivalent to @samp{shell make @var{make-args}}.
>  @end table
>  
> +@table @code
> +@kindex pipe
> +@kindex |
> +@cindex send the output of a gdb command to a shell command
> +@anchor{pipe}
> +@item pipe [@var{command}] | @var{shell_command}
> +@itemx | [@var{command}] | @var{shell_command}
> +@itemx pipe -d @var{sep} @var{command} @var{sep} @var{shell_command}
> +@itemx | -d @var{sep} @var{command} @var{sep} @var{shell_command}
> +Executes @var{command} and sends its output to @var{shell_command}.
> +Note that no space is needed around @code{|}.
> +If no @var{command} is provided, the last command executed is repeated.
> +
> +If the @var{command} contains a @code{|}, then the option @code{-d @var{sep}}
> +can be used to specify an alternate separator string @var{sep} that separates
> +the  @var{command} from the @var{shell_command}.
> +

(spurious double space after "the" in the last line.)

Like in the "help" output, I think we can improve this a bit with a slight
copy/edit.  "If contains |, then" suggests that you can only use -d
if the command contains "|", which is obviously not really the intention.

I'd suggest:

 In case the @var{command} contains a @code{|}, the option @code{-d @var{sep}}
 can be used to specify an alternate separator string @var{sep} that separates
 the @var{command} from the @var{shell_command}.

"in case" suggests a precautionary measure.

> +Example:
> +@smallexample
> +@group
> +(gdb) pipe p full|wc
> +      5      17      81
> +(gdb) |p full|wc -l
> +5
> +@end group
> +@group
> +(gdb) p full
> +$4 = (black => 144,
> +  red => 233,
> +  green => 377,
> +  blue => 610,
> +  white => 987)
> +(gdb) ||grep red
> +  red => 233,

I'd suggest printing "p full" before the pipe commands.
I read this top to bottom and it took me a second to realize
what "full" was.  Maybe rename it to "var" or something like that,
while at it.

Use "$1" for value history number.

( I guess that's Ada syntax.  I'd hazard a guess that a significant
number of GDB users don't know Ada.  :-) )

> +@end group
> +@group
> +(gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
> +this contains a PIPE char
> +(gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
> +this contains a PIPE char!
> +(gdb)
> +@end group
> +@end smallexample
> +@end table
> +
> +The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
> +can be used to examine the exit status of the last shell command launched
> +by @code{shell}, @code{make}, @code{pipe} and @code{|}.
> +@xref{Convenience Vars,, Convenience Variables}.
> +
>  @node Logging Output
>  @section Logging Output
>  @cindex logging @value{GDBN} output
> @@ -1482,6 +1532,8 @@ Set @code{redirect} if you want output to go only to the log file.
>  Show the current values of the logging settings.
>  @end table
>  
> +You can also redirect the output of a @value{GDBN} command to a
> +shell command.  @xref{pipe}.
>  @node Commands
>  @chapter @value{GDBN} Commands
>  
> @@ -11292,6 +11344,21 @@ the value 12 for @code{$_gdb_minor}.  These variables allow you to
>  write scripts that work with different versions of @value{GDBN}
>  without errors caused by features unavailable in some of those
>  versions.
> +
> +@item $_shell_exitcode
> +@itemx $_shell_exitsignal
> +@vindex $_shell_exitcode@r{, convenience variable}
> +@vindex $_shell_exitsignal@r{, convenience variable}
> +@cindex shell command, exit code
> +@cindex shell command, exit signal
> +@cindex exit status of shell commands
> +@value{GDBN} commands such as @code{shell}, @code{|} are launching

List of two items -> use "and", not ",", thus:

   @code{shell} and @code{|}

> +shell commands.  When a launched command terminates, @value{GDBN}
> +automatically maintains the variables @code{$_shell_exitcode}
> +and @code{$_shell_exitsignal} according to the exit status of the last
> +launched command.  These variables are set and used similarly to
> +the variables @code{$_exitcode} and @code{$_exitsignal}.
> +
>  @end table
>  
>  @node Convenience Funs
> 

Thanks,
Pedro Alves