Re: [PATCH] Implementation of pipe to pass GDB's command output to the shell.

[Abhijit Halder <abhijit dot k dot halder at gmail dot com>]

On Tue, Jan 3, 2012 at 10:34 PM, Abhijit Halder
<abhijit.k.halder@gmail.com> wrote:
> Hi all,
>
> The copyright assignment is yet to be accomplished, it's almost in
> final stage. Meanwhile I want you to please do a final review of the
> changes I made.
>
> This patch implements a new gdb command namely, "pipe" to pass gdb
> command output to a shell command for further processing. This patch
> includes necessary documentation change and test-cases as well.
>
> Thanks,
> Abhijit Halder

One last minute correction.

>+/* Run execute_command for PIPE and FROM_TTY.  Write output to the pipe, do not
>+   display it to the screen.  */
>+
>+static void
>+execute_command_to_pipe (struct pipe_obj *pipe, int from_tty)
>+{
>+  char *argv[4];
>+  struct cleanup *cleanup;
>+  struct ui_file *fp;
>+  int status;
>+  const char *errmsg;
>+  volatile struct gdb_exception exception;
>+  const char *shell;

Thie following correction is required to fix compilation error.
char *shell;

>+
>+  if (*pipe->gdb_cmd == '\0')
>+    error (_("No gdb-command is specified."));
>+

Attachment: ChangeLog.txt
Description: Text document

diff -rup src/gdb/doc/gdb.texinfo dst/gdb/doc/gdb.texinfo
--- src/gdb/doc/gdb.texinfo	2012-01-06 14:46:43.881568021 +0530
+++ dst/gdb/doc/gdb.texinfo	2012-01-06 15:59:08.945568207 +0530
@@ -1367,6 +1367,56 @@ Execute the @code{make} program with the
 arguments.  This is equivalent to @samp{shell make @var{make-args}}.
 @end table
 
+If you want to process the output of a @value{GDBN} command using some shell
+command or some script, that can be done by using the command @code{pipe}.
+
+@table @code
+@kindex pipe
+@item pipe @var{dlim} @var{gdbcmd} @var{dlim} @var{shellcmd}
+@var{dlim} is a string of arbitrary length, containing no whitespace and no
+leading @samp{-}, acts as a separator between a @value{GDBN} command
+@var{gdbcmd} and a shell command @var{shellcmd}.  The shell command should be
+in compliance with the syntax of the shell.  The @var{dlim} pattern should not
+appear in @var{gdbcomd}, otherwise the parsing will fail; although it may
+appear in @var{shellcmd}.
+
+If exists, the environment variable @code{SHELL} determines in which shell to
+run the shell command.  Otherwise @value{GDBN} uses the default shell
+(@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
+@end table
+
+@smallexample
+(@value{GDBP}) @b{ptype dd_tbl}
+type = struct dd @{
+    int dd_handle;
+    const char *dd_name;
+    int dd_major;
+    int dd_minor;
+    void *dd_code;
+    void *dd_data;
+@} [1024]
+(@value{GDBP}) @b{pipe <br> print dd_tbl <br> sed 's/@}/\n/g' | grep @
+"\.test_dd" | tr ',' '\n'}
+
+  @{dd_handle = 10
+  dd_name = 0x8048538 ".test_dd"
+  dd_major = 100
+  dd_minor = 0
+  dd_code = 0xcc
+  dd_data = 0x80
+@end smallexample
+
+In the above example @samp{<br>} acts as a delimiter.  The output of
+@samp{print dd_tbl} is passed to the shell command @samp{sed 's/@}/\n/g' | @
+grep ".test_dd" | tr ',' '\n'} for processing.  @samp{|} could be one of the
+natural choise of being used as the delimiter.  In the above example we have
+avoided the same for readability purpose.
+
+In the given example the output of @value{GDBN} command @samp{print dd_tbl} is
+huge and not well formated.  The use of shell commands like @command{sed},
+@command{tr} and @command{grep} ease the searching of desired pattern and hence
+ease debugging.
+
 @node Logging Output
 @section Logging Output
 @cindex logging @value{GDBN} output
diff -rup src/gdb/Makefile.in dst/gdb/Makefile.in
--- src/gdb/Makefile.in	2012-01-06 15:48:37.405568350 +0530
+++ dst/gdb/Makefile.in	2012-01-06 15:59:08.945568207 +0530
@@ -718,7 +718,7 @@ SFILES = ada-exp.y ada-lang.c ada-typepr
 	objc-exp.y objc-lang.c \
 	objfiles.c osabi.c observer.c osdata.c \
 	opencl-lang.c \
-	p-exp.y p-lang.c p-typeprint.c p-valprint.c parse.c printcmd.c \
+	p-exp.y p-lang.c p-typeprint.c p-valprint.c parse.c pipe.c printcmd.c \
 	proc-service.list progspace.c \
 	prologue-value.c psymtab.c \
 	regcache.c reggroups.c remote.c remote-fileio.c reverse.c \
@@ -875,7 +875,7 @@ COMMON_OBS = $(DEPFILES) $(CONFIG_OBS) $
 	mi-common.o \
 	event-loop.o event-top.o inf-loop.o completer.o \
 	gdbarch.o arch-utils.o gdbtypes.o osabi.o copying.o \
-	memattr.o mem-break.o target.o parse.o language.o buildsym.o \
+	memattr.o mem-break.o target.o parse.o pipe.o language.o buildsym.o \
 	findcmd.o \
 	std-regs.o \
 	signals.o \
diff -rup src/gdb/NEWS dst/gdb/NEWS
--- src/gdb/NEWS	2012-01-03 19:38:09.721001462 +0530
+++ dst/gdb/NEWS	2012-01-06 15:59:08.945568207 +0530
@@ -138,6 +138,9 @@
   "!" is now an alias of the "shell" command.
   Note that no space is needed between "!" and SHELL COMMAND.
 
+* New command "pipe" has been added to make GDB's command output available to a
+  shell command for processing.
+
 * Changed commands
 
 watch EXPRESSION mask MASK_VALUE
diff -rup src/gdb/pipe.c dst/gdb/pipe.c
--- src/gdb/pipe.c	2012-01-06 15:48:14.917568019 +0530
+++ dst/gdb/pipe.c	2012-01-06 15:59:08.945568207 +0530
@@ -0,0 +1,239 @@
+/* Everything about pipe command, for GDB.
+
+   Copyright (C) 2012 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include <ctype.h>
+#include "gdb_string.h"
+#include "ui-file.h"
+#include "ui-out.h"
+#include "cli/cli-utils.h"
+#include "gdbcmd.h"
+#include "libiberty.h"
+#include "exceptions.h"
+
+#if defined (__MINGW32__)
+# define DEFAULT_SHELL "cmd.exe"
+# define OPTION_TO_SHELL "/c"
+#else
+# define DEFAULT_SHELL "/bin/sh"
+# define OPTION_TO_SHELL "-c"
+#endif
+
+/* Structure to encapsulate all entities associated with pipe.  */
+
+struct pipe_obj
+{
+  /* The delimiter to separate out gdb-command and shell-command.  This can be
+     any arbitrary string without containing any whitespace.  There should not
+     be any leading '-' in the delimiter.  */
+  char *dlim;
+
+  /* The gdb-command.  */
+  char *gdb_cmd;
+
+  /* The shell-command.  */
+  char *shell_cmd;
+
+  /* The gdb-side stream pointer to the pipe.  */
+  FILE *handle;
+
+  /* The pex object used to create pipeline between gdb and shell.  */
+  struct pex_obj *pex;
+};
+
+/* Destruct pipe object referenced by ARG.  */
+
+static void
+destruct_pipe (void *arg)
+{
+  struct pipe_obj *pipe = (struct pipe_obj *) arg;
+
+  if (pipe->handle != NULL)
+    fclose (pipe->handle);
+
+  if (pipe->pex != NULL)
+    {
+      int status;
+
+      /* Wait till the process on the other side of the pipe completes its
+	 job before closing its file descriptors.  */
+      pex_get_status (pipe->pex, 1, &status);
+
+      if (!WIFEXITED (status))
+	warning (_("Execution of shell-command `%s' may not be completed: %s."),
+		 pipe->shell_cmd, safe_strerror (status));
+
+      pex_free (pipe->pex);
+    }
+
+  xfree (pipe->dlim);
+  xfree (pipe);
+}
+
+/* Construct a pipe object by parsing argument ARG to the pipe command.  */
+
+static struct pipe_obj *
+construct_pipe (const char *arg)
+{
+  struct pipe_obj *pipe;
+  struct cleanup *cleanup;
+  char *p, *t;
+
+  if (arg == NULL)
+    error (_("No argument is specified."));
+
+  pipe = XCNEW (struct pipe_obj);
+  cleanup = make_cleanup (destruct_pipe, pipe);
+
+  p = xstrdup (arg);
+  pipe->dlim = p;
+
+  if (*pipe->dlim == '-')
+    error (_("Delimiter pattern should not start with `-'."));
+
+  t = skip_to_space (p);
+  p = skip_spaces (t);
+
+  if (*p == '\0')
+    error (_("No gdb-command is specified."));
+
+  *t = '\0';
+  pipe->gdb_cmd = p;
+
+  for (;;)
+    {
+      t = skip_to_space (p);
+
+      if (*t == '\0')
+	error (_("No shell-command is specified."));
+
+      /* Check whether the token separated by whitespace matches with
+	 delimiter.  */ 
+      if (memcmp (p, pipe->dlim, (t - p)) == 0
+	  && pipe->dlim[t - p] == '\0')
+	{
+	  *p = '\0';
+	  pipe->shell_cmd = skip_spaces (t);
+	  break;
+	}
+
+       p = skip_spaces (t);
+    }
+
+  discard_cleanups (cleanup);
+  return pipe;
+}
+
+/* Run execute_command for PIPE and FROM_TTY.  Write output to the pipe, do not
+   display it to the screen.  */
+
+static void
+execute_command_to_pipe (struct pipe_obj *pipe, int from_tty)
+{
+  char *argv[4];
+  struct cleanup *cleanup;
+  struct ui_file *fp;
+  int status;
+  const char *errmsg;
+  volatile struct gdb_exception exception;
+  char *shell;
+
+  if (*pipe->gdb_cmd == '\0')
+    error (_("No gdb-command is specified."));
+
+  /* Figure out what shell the user program is under.  */
+  shell = getenv ("SHELL");
+  if (shell == NULL)
+    shell = DEFAULT_SHELL;
+
+  argv[0] = shell;
+  argv[1] = OPTION_TO_SHELL;
+  argv[2] = pipe->shell_cmd;
+  argv[3] = NULL;
+
+  pipe->pex = pex_init (PEX_USE_PIPES, argv[0], NULL);
+  pipe->handle = pex_input_pipe (pipe->pex, 0);
+
+  if (pipe->handle == NULL)
+    error (_("Failed to create pipe: %s."), safe_strerror (errno));
+
+  errmsg = pex_run (pipe->pex, PEX_LAST, argv[0], argv, NULL, NULL, &status);
+
+  if (errmsg != NULL)
+    error (_("Failed to execute shell-command `%s' on pipe: %s: %s."),
+	   pipe->shell_cmd, errmsg, safe_strerror (status));
+
+  /* GDB_STDOUT should be better already restored during these
+     restoration callbacks.  */
+  cleanup = set_batch_flag_and_make_cleanup_restore_page_info ();
+  fp = stdio_fileopen (pipe->handle);
+  make_cleanup_ui_file_delete (fp);
+  make_cleanup_restore_ui_file (&gdb_stdout);
+  make_cleanup_restore_ui_file (&gdb_stderr);
+  make_cleanup_restore_ui_file (&gdb_stdlog);
+  make_cleanup_restore_ui_file (&gdb_stdtarg);
+  make_cleanup_restore_ui_file (&gdb_stdtargerr);
+
+  if (ui_out_redirect (current_uiout, fp) < 0)
+    warning (_("Current output protocol does not support redirection"));
+  else 
+    make_cleanup_ui_out_redirect_pop (current_uiout);
+
+  gdb_stdout = fp;
+  gdb_stderr = fp;
+  gdb_stdlog = fp;
+  gdb_stdtarg = fp;
+  gdb_stdtargerr = fp;
+
+  TRY_CATCH (exception, RETURN_MASK_ERROR)
+    {
+      execute_command (pipe->gdb_cmd, from_tty);
+    }
+
+  if (exception.reason < 0)
+    exception_print (gdb_stderr, exception);
+
+  do_cleanups (cleanup);
+}
+
+/* Execute the pipe command with argument ARG and FROM_TTY.  */
+
+static void
+pipe_command (char *arg, int from_tty)
+{
+  struct pipe_obj *pipe = construct_pipe (arg);
+  struct cleanup *cleanup = make_cleanup (destruct_pipe, pipe);
+
+  execute_command_to_pipe (pipe, from_tty);
+  do_cleanups (cleanup);
+}
+
+/* Module initialization.  */
+
+void
+_initialize_pipe (void)
+{
+  add_cmd ("pipe", no_class, pipe_command, _("\
+Create pipe to pass gdb-command output to a shell command for processing.\n\
+Arguments are a delimiter, followed by a gdb-command, then the same\n\
+delimiter again and finally a shell-command.\n\n\
+The delimiter can be a string of arbitrary length containing no whitespace\n\
+and should not have any leading `-'."),
+	   &cmdlist);
+}
diff -rup src/gdb/testsuite/gdb.base/pipe.exp dst/gdb/testsuite/gdb.base/pipe.exp
--- src/gdb/testsuite/gdb.base/pipe.exp	2011-09-13 16:37:04.294277252 +0530
+++ dst/gdb/testsuite/gdb.base/pipe.exp	2012-01-06 15:59:08.945568207 +0530
@@ -0,0 +1,51 @@
+# Copyright 2012 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#
+# test gdb pipe commands
+#
+
+set test "pipe"
+set tempfile ${objdir}/${subdir}/${test}.x
+
+gdb_exit
+gdb_start
+
+gdb_test "pipe" "No argument is specified"
+gdb_test "pipe |" "No gdb-command is specified"
+gdb_test "pipe -x" "Delimiter pattern should not start with '-'"
+gdb_test "pipe | print 'x'" "No shell-command is specified"
+gdb_test "pipe | print 'x' |< cat" "No shell-command is specified"
+gdb_test "pipe |< print 'x' | cat" "No shell-command is specified"
+gdb_test "pipe | print 'x' >| cat" "No shell-command is specified"
+gdb_test "pipe >| print 'x' | cat" "No shell-command is specified"
+gdb_test "pipe | print 'x' | cat" " = 120 'x'"
+gdb_test "pipe | print 'x' | cat | cat" " = 120 'x'"
+
+file delete $tempfile
+gdb_test_no_output "pipe | p 'x' | cat >$tempfile"
+if ![file exists $tempfile] then {
+    perror "$tempfile does not exist."
+    return 0
+} else {
+    set fp [open $tempfile r]
+    set fdata [read $fp]
+    close $fp
+    if ![regexp {^\$[0-9]+ = 120 'x'\n$} $fdata] then {
+	fail $test
+    } else {
+	pass $test
+    }
+}

Attachment: doc-ChangeLog.txt
Description: Text document

Attachment: testsuite-ChangeLog.txt
Description: Text document