Implement redirection of output from NSH builtin commands to a file in a mounted volume

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5521 42af7a65-404d-4744-a932-0658087f49c3

ChangeLog.txt

@@ -467,3 +467,5 @@
 	* apps/examples/ostest/waitpid.c:  Add a test for waitpid(), waitid(),
 	  and wait().
 	* builtin/binfs.c:  Add hooks for dup() method (not implemented).
+	* builtin/exec_builtin.c, nshlib/nsh_parse.c, and nshlib/nsh_builtin.c:
+	  NSH now supports re-direction of I/O to files (but still not from).

builtin/Kconfig

@@ -27,4 +27,13 @@ if BUILTIN
 		however, to support execution of the builtin applications from BINFS as
 		well (via a binfmt/ loader).  However, that is down the road.
 
+config BUILTIN_PROXY_STACKSIZE
+	int "Builtin Proxy Stack Size"
+	default 1024
+	---help---
+		If exec_builting uses I/O redirection options, then it will require
+		an intermediary/proxy task to muck with the file descriptors.  This
+		configuration item specifies the stack size used for the proxy. Default:
+		1024 bytes.
+
 endif

builtin/binfs.c

@@ -399,7 +399,7 @@ static int binfs_readdir(struct inode *mountpt, struct fs_dirent_s *dir)
   /* Have we reached the end of the directory */
 
   index = dir->u.binfs.fb_index;
-  if (builtins[index].name == NULL)
+  if (g_builtins[index].name == NULL)
     {
       /* We signal the end of the directory by returning the
        * special error -ENOENT
@@ -412,9 +412,9 @@ static int binfs_readdir(struct inode *mountpt, struct fs_dirent_s *dir)
     {
       /* Save the filename and file type */
 
-      fvdbg("Entry %d: \"%s\"\n", index, builtins[index].name);
+      fvdbg("Entry %d: \"%s\"\n", index, g_builtins[index].name);
       dir->fd_dir.d_type = DTYPE_FILE;
-      strncpy(dir->fd_dir.d_name, builtins[index].name, NAME_MAX+1);
+      strncpy(dir->fd_dir.d_name, g_builtins[index].name, NAME_MAX+1);
 
       /* The application list is terminated by an entry with a NULL name.
        * Therefore, there is at least one more entry in the list.

builtin/builtin.c

@@ -64,7 +64,7 @@ extern "C" {
 
 #include "builtin_proto.h"
 
-const struct builtin_s builtins[] =
+const struct builtin_s g_builtins[] =
 {
 # include "builtin_list.h"
   { NULL, 0, 0, 0 }
@@ -90,7 +90,7 @@ const struct builtin_s builtins[] =
 
 int number_builtins(void)
 {
-  return sizeof(builtins)/sizeof(struct builtin_s) - 1;
+  return sizeof(g_builtins)/sizeof(struct builtin_s) - 1;
 }
 
 

builtin/builtin.h

@@ -60,7 +60,7 @@ extern "C" {
 #define EXTERN extern
 #endif
 
-EXTERN const struct builtin_s builtins[];
+EXTERN const struct builtin_s g_builtins[];
 
 /****************************************************************************
  * Public Functions

builtin/exec_builtin.c

@@ -1,13 +1,15 @@
 /****************************************************************************
  * apps/builtin/exec_builtin.c
  *
+ * Originally by:
+ *
  *   Copyright (C) 2011 Uros Platise. All rights reserved.
  *   Author: Uros Platise <uros.platise@isotel.eu>
  *
- * With updates, modifications, and general maintenance by:
+ * With subsequent updates, modifications, and general maintenance by:
  *
- *   Copyright (C) 2012 Gregory Nutt.  All rights reserved.
+ *   Copyright (C) 2012-2013 Gregory Nutt.  All rights reserved.
- *   Auther: Gregory Nutt <gnutt@nuttx.org>
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -43,18 +45,45 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
-#include <apps/apps.h>
-#include <sched.h>
 
+#include <sched.h>
 #include <string.h>
+#include <fcntl.h>
+#include <semaphore.h>
 #include <errno.h>
+#include <debug.h>
+
+#include <apps/apps.h>
 
 #include "builtin.h"
 
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#ifndef CONFIG_BUILTIN_PROXY_STACKSIZE
+#  define CONFIG_BUILTIN_PROXY_STACKSIZE 1024
+#endif
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
 
+struct builtin_parms_s
+{
+  /* Input values */
+
+  FAR const char *redirfile;
+  FAR const char **argv;
+  int oflags;
+  int index;
+
+  /* Returned values */
+
+  pid_t result;
+  int errcode;
+};
+
 /****************************************************************************
  * Private Function Prototypes
  ****************************************************************************/
@@ -63,10 +92,276 @@
  * Private Data
  ****************************************************************************/
 
+static sem_t g_builtin_parmsem = SEM_INITIALIZER(1);
+static sem_t g_builtin_execsem = SEM_INITIALIZER(0);
+static struct builtin_parms_s g_builtin_parms;
+
 /****************************************************************************
  * Private Functions
  ****************************************************************************/
 
+/****************************************************************************
+ * Name: bultin_semtake and builtin_semgive
+ *
+ * Description:
+ *   Give and take semaphores
+ *
+ * Input Parameters:
+ *
+ *   sem - The semaphore to act on.
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+static void bultin_semtake(FAR sem_t *sem)
+{
+  int ret;
+
+  do
+    {
+      ret = sem_wait(sem);
+      ASSERT(ret == 0 || errno == EINTR);
+    }
+  while (ret != 0);
+}
+
+#define builtin_semgive(sem) sem_post(sem)
+
+/****************************************************************************
+ * Name: builtin_taskcreate
+ *
+ * Description:
+ *   Execute the builtin task
+ *
+ * Returned Value:
+ *   On success, the task ID of the builtin task is returned; On failure, -1
+ *  (ERROR) is returned and the errno is set appropriately.
+ *
+ ****************************************************************************/
+
+static int builtin_taskcreate(int index, FAR const char **argv)
+{
+  int ret;
+
+  /* Disable pre-emption.  This means that although we start the builtin
+   * application here, it will not actually run until pre-emption is
+   * re-enabled below.
+   */
+
+  sched_lock();
+
+  /* Start the builtin application task */
+
+  ret = TASK_CREATE(g_builtins[index].name, g_builtins[index].priority,
+                    g_builtins[index].stacksize, g_builtins[index].main,
+                    (argv) ? &argv[1] : (FAR const char **)NULL);
+
+  /* If robin robin scheduling is enabled, then set the scheduling policy
+   * of the new task to SCHED_RR before it has a chance to run.
+   */
+
+#if CONFIG_RR_INTERVAL > 0
+  if (ret > 0)
+    {
+      struct sched_param param;
+
+      /* Pre-emption is disabled so the task creation and the
+       * following operation will be atomic.  The priority of the
+       * new task cannot yet have changed from its initial value.
+       */
+
+      param.sched_priority = g_builtins[index].priority;
+      (void)sched_setscheduler(ret, SCHED_RR, &param);
+    }
+#endif
+
+  /* Now let the builtin application run */
+
+  sched_unlock();
+
+  /* Return the task ID of the new task if the task was sucessfully
+   * started.  Otherwise, ret will be ERROR (and the errno value will
+   * be set appropriately).
+   */
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: builtin_proxy
+ *
+ * Description:
+ *   Perform output redirection, then execute the builtin task.
+ *
+ * Input Parameters:
+ *   Standard task start-up parameters
+ *
+ * Returned Value:
+ *   Standard task return value.
+ *
+ ****************************************************************************/
+
+static int builtin_proxy(int argc, char *argv[])
+{
+  int fd;
+  int ret = ERROR;
+
+  /* Open the output file for redirection */
+
+  svdbg("Open'ing redirfile=%s oflags=%04x mode=0644\n",
+        g_builtin_parms.redirfile, g_builtin_parms.oflags);
+
+  fd = open(g_builtin_parms.redirfile, g_builtin_parms.oflags, 0644);
+  if (fd < 0)
+    {
+      /* Remember the errno value.  ret is already set to ERROR */
+
+      g_builtin_parms.errcode = errno;
+      sdbg("ERROR: open of %s failed: %d\n",
+           g_builtin_parms.redirfile, g_builtin_parms.errcode);
+    }
+
+  /* Does the return file descriptor happen to match the required file
+   * desciptor number?
+   */
+
+  else if (fd != 1)
+    {
+      /* No.. dup2 to get the correct file number */
+
+      svdbg("Dup'ing %d->1\n", fd);
+
+      ret = dup2(fd, 1);
+      if (ret < 0)
+        {
+          g_builtin_parms.errcode = errno;
+          sdbg("ERROR: dup2 failed: %d\n", g_builtin_parms.errcode);
+        }
+
+      svdbg("Closing fd=%d\n", fd);
+      close(fd);
+    }
+
+  /* Was the setup successful? */
+
+  if (ret == OK)
+    {
+      /* Yes.. Start the task.  On success, the task ID of the builtin task
+       * is returned; On failure, -1 (ERROR) is returned and the errno
+       * is set appropriately.
+       */
+
+      ret = builtin_taskcreate(g_builtin_parms.index, g_builtin_parms.argv);
+      if (ret < 0)
+        {
+          g_builtin_parms.errcode = errno;
+          sdbg("ERROR: builtin_taskcreate failed: %d\n",
+               g_builtin_parms.errcode);
+        }
+    }
+
+  /* Post the semaphore to inform the parent task that we have completed
+   * what we need to do.
+   */
+
+  g_builtin_parms.result = ret;
+  builtin_semgive(&g_builtin_execsem);
+  return 0;
+}
+
+/****************************************************************************
+ * Name: builtin_startproxy
+ *
+ * Description:
+ *   Perform output redirection, then execute the builtin task.
+ *
+ * Input Parameters:
+ *   Standard task start-up parameters
+ *
+ * Returned Value:
+ *   On success, the task ID of the builtin task is returned; On failure, -1
+ *  (ERROR) is returned and the errno is set appropriately.
+ *
+ ****************************************************************************/
+
+static inline int builtin_startproxy(int index, FAR const char **argv,
+                                     FAR const char *redirfile, int oflags)
+{
+  struct sched_param param;
+  pid_t proxy;
+  int errcode;
+  int ret;
+
+  DEBUGASSERT(path);
+
+  svdbg("index=%d argv=%p redirfile=%s oflags=%04x\n",
+        index, argv, redirfile, oflags);
+
+  /* We will have to go through an intermediary/proxy task in order to
+   * perform the I/O redirection.  This would be a natural place to fork().
+   * However, true fork() behavior requires an MMU and most implementations
+   * of vfork() are not capable of these operations.
+   *
+   * Even without fork(), we can still do the job, but parameter passing is
+   * messier.  Unfortunately, there is no (clean) way to pass binary values
+   * as a task parameter, so we will use a semaphore-protected global
+   * structure.
+   */
+
+  /* Get exclusive access to the global parameter structure */
+
+  bultin_semtake(&g_builtin_parmsem);
+
+  /* Populate the parameter structure */
+
+  g_builtin_parms.redirfile = redirfile;
+  g_builtin_parms.argv      = argv;
+  g_builtin_parms.result    = ERROR;
+  g_builtin_parms.oflags    = oflags;
+  g_builtin_parms.index     = index;
+
+  /* Get the priority of this (parent) task */
+
+  ret = sched_getparam(0, &param);
+  if (ret < 0)
+    {
+      errcode = errno;
+      sdbg("ERROR: sched_getparam failed: %d\n", errcode);
+      goto errout;
+    }
+
+  /* Start the intermediary/proxy task at the same priority as the parent task. */
+
+  proxy = TASK_CREATE("builtin_proxy", param.sched_priority,
+                      CONFIG_BUILTIN_PROXY_STACKSIZE, (main_t)builtin_proxy,
+                      (FAR const char **)NULL);
+  if (proxy < 0)
+    {
+      errcode = errno;
+      sdbg("ERROR: Failed to start builtin_proxy: %d\n", errcode);
+      goto errout;
+    }
+
+   /* Wait for the proxy to complete its job.  We could use waitpid()
+    * for this.
+    */
+
+   bultin_semtake(&g_builtin_execsem);
+
+   /* Get the result and relinquish our access to the parameter structure */
+
+   set_errno(g_builtin_parms.errcode);
+   builtin_semgive(&g_builtin_parmsem);
+   return g_builtin_parms.result;
+
+errout:
+  set_errno(errcode);
+  builtin_semgive(&g_builtin_parmsem);
+  return ERROR;
+}
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -87,7 +382,7 @@ const char *builtin_getname(int index)
      return NULL;
    }
 
-  return builtins[index].name;
+  return g_builtins[index].name;
 }
 
 /****************************************************************************
@@ -103,9 +398,9 @@ int builtin_isavail(FAR const char *appname)
 {
   int i;
 
-  for (i = 0; builtins[i].name; i++) 
+  for (i = 0; g_builtins[i].name; i++)
     {
-      if (!strcmp(builtins[i].name, appname))
+      if (!strcmp(g_builtins[i].name, appname))
         {
           return i;
         }
@@ -116,72 +411,58 @@ int builtin_isavail(FAR const char *appname)
 }
 
 /****************************************************************************
- * Name: builtin_isavail
+ * Name: exec_builtin
  *
  * Description:
- *   Execute the application with name 'appname', providing the arguments
+ *   Executes builtin applications registered during 'make context' time.
- *   in the argv[] array.
+ *   New application is run in a separate task context (and thread).
+ *
+ * Input Parameter:
+ *   filename  - Name of the linked-in binary to be started.
+ *   argv      - Argument list
+ *   redirfile - If output if redirected, this parameter will be non-NULL
+ *               and will provide the full path to the file.
+ *   oflags    - If output is redirected, this parameter will provide the
+ *               open flags to use.  This will support file replacement
+ *               of appending to an existing file.
  *
  * Returned Value:
- *   On success, the task ID of the builtin application is returned.  On
+ *   This is an end-user function, so it follows the normal convention:
- *   failure, -1 (ERROR) is returned an the errno value is set appropriately.
+ *   Returns the PID of the exec'ed module.  On failure, it.returns
+ *   -1 (ERROR) and sets errno appropriately.
  *
  ****************************************************************************/
 
-int exec_builtin(FAR const char *appname, FAR const char **argv)
+int exec_builtin(FAR const char *appname, FAR const char **argv,
+                 FAR const char *redirfile, int oflags)
 {
-  pid_t pid;
   int index;
+  int ret = ERROR;
 
   /* Verify that an application with this name exists */
 
   index = builtin_isavail(appname);
   if (index >= 0)
     {
-      /* Disable pre-emption.  This means that although we start the builtin
+      /* Is output being redirected? */
-       * application here, it will not actually run until pre-emption is
-       * re-enabled below.
-       */
-
-      sched_lock();
 
+      if (redirfile)
+        {
+          ret = builtin_startproxy(index, argv, redirfile, oflags);
+        }
+      else
+        {
           /* Start the builtin application task */
 
-      pid = TASK_CREATE(builtins[index].name, builtins[index].priority, 
+          ret = builtin_taskcreate(index, argv);
-                        builtins[index].stacksize, builtins[index].main, 
+        }
-                        (argv) ? &argv[1] : (const char **)NULL);
-
-      /* If robin robin scheduling is enabled, then set the scheduling policy
-       * of the new task to SCHED_RR before it has a chance to run.
-       */
-
-#if CONFIG_RR_INTERVAL > 0
-      if (pid > 0)
-        {
-          struct sched_param param;
-
-          /* Pre-emption is disabled so the task creation and the
-           * following operation will be atomic.  The priority of the
-           * new task cannot yet have changed from its initial value.
-           */
-
-          param.sched_priority = builtins[index].priority;
-          sched_setscheduler(pid, SCHED_RR, &param);
     }
-#endif
-      /* Now let the builtin application run */
 
-      sched_unlock();
 
   /* Return the task ID of the new task if the task was sucessfully
-       * started.  Otherwise, pid will be ERROR (and the errno value will
+   * started.  Otherwise, ret will be ERROR (and the errno value will
    * be set appropriately).
    */
 
-      return pid;
+  return ret;
-    }
-
-  /* Return ERROR with errno set appropriately */
-
-  return ERROR;
 }

include/apps.h

@@ -1,9 +1,16 @@
 /****************************************************************************
  * apps/include/apps.h
  *
- *   Copyright(C) 2011 Uros Platise. All rights reserved.
+ * Originally by:
+ *
+ *   Copyright (C) 2011 Uros Platise. All rights reserved.
  *   Author: Uros Platise <uros.platise@isotel.eu>
  *
+ * With subsequent updates, modifications, and general maintenance by:
+ *
+ *   Copyright (C) 2012-2013 Gregory Nutt.  All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -64,19 +71,6 @@ struct builtin_s
  * Public Data
  ****************************************************************************/
 
-/* The "bindir" is file system that supports access to the builtin applications.
- * It is typically mounted under /bin.
- */
-
-#ifdef CONFIG_APPS_BINDIR
-struct mountpt_operations;
-extern const struct mountpt_operations binfs_operations;
-#endif
-
-/****************************************************************************
- * Public Functions
- ****************************************************************************/
-
 #undef EXTERN
 #if defined(__cplusplus)
 #define EXTERN extern "C"
@@ -85,6 +79,19 @@ extern "C" {
 #define EXTERN extern
 #endif
 
+/* The "bindir" is file system that supports access to the builtin applications.
+ * It is typically mounted under /bin.
+ */
+
+#ifdef CONFIG_APPS_BINDIR
+EXTERN mountpt_operations;
+EXTERN const struct mountpt_operations binfs_operations;
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
 /****************************************************************************
  * Name: builtin_isavail
  *
@@ -131,6 +138,11 @@ EXTERN const char *builtin_getname(int index);
  * Input Parameter:
  *   filename  - Name of the linked-in binary to be started.
  *   argv      - Argument list
+ *   redirfile - If output if redirected, this parameter will be non-NULL
+ *               and will provide the full path to the file.
+ *   oflags    - If output is redirected, this parameter will provide the
+ *               open flags to use.  This will support file replacement
+ *               of appending to an existing file.
  *
  * Returned Value:
  *   This is an end-user function, so it follows the normal convention:
@@ -139,7 +151,8 @@ EXTERN const char *builtin_getname(int index);
  *
  ****************************************************************************/
 
-EXTERN int exec_builtin(FAR const char *appname, FAR const char **argv);
+EXTERN int exec_builtin(FAR const char *appname, FAR const char **argv,
+                        FAR const char *redirfile, int oflags);
 
 #undef EXTERN
 #if defined(__cplusplus)

nshlib/Makefile

@@ -44,7 +44,7 @@ CSRCS = nsh_init.c nsh_parse.c nsh_console.c nsh_fscmds.c nsh_ddcmd.c \
 		nsh_proccmds.c nsh_mmcmds.c nsh_envcmds.c nsh_dbgcmds.c
 
 ifeq ($(CONFIG_NSH_BUILTIN_APPS),y)
-CSRCS += nsh_apps.c
+CSRCS += nsh_builtin.c
 endif
 
 ifeq ($(CONFIG_NSH_ROMFSETC),y)

nshlib/nsh.h

@@ -491,7 +491,8 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline);
 /* Application interface */
 
 #ifdef CONFIG_NSH_BUILTIN_APPS
-int nsh_execapp(FAR struct nsh_vtbl_s *vtbl, FAR const char *cmd, FAR char **argv);
+int nsh_builtin(FAR struct nsh_vtbl_s *vtbl, FAR const char *cmd,
+                FAR char **argv, FAR const char *redirfile, int oflags);
 #endif
 
 /* Working directory support */

nshlib/nsh_builtin.c

@@ -1,10 +1,16 @@
 /****************************************************************************
- * apps/nshlib/nsh_apps.c
+ * apps/nshlib/nsh_builtin.c
+ *
+ * Originally by:
  *
- *   Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
  *   Copyright (C) 2011 Uros Platise. All rights reserved.
  *   Author: Uros Platise <uros.platise@isotel.eu>
  *
+ * With subsequent updates, modifications, and general maintenance by:
+ *
+ *   Copyright (C) 2011-2013 Gregory Nutt.  All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -84,7 +90,7 @@
  ****************************************************************************/
 
 /****************************************************************************
- * Name: nsh_execapp
+ * Name: nsh_builtin
  *
  * Description:
  *    Attempt to execute the application task whose name is 'cmd'
@@ -104,8 +110,8 @@
  *
  ****************************************************************************/
 
-int nsh_execapp(FAR struct nsh_vtbl_s *vtbl, FAR const char *cmd,
+int nsh_builtin(FAR struct nsh_vtbl_s *vtbl, FAR const char *cmd,
-                FAR char **argv)
+                FAR char **argv, FAR const char *redirfile, int oflags)
 {
   int ret = OK;
 
@@ -119,7 +125,7 @@ int nsh_execapp(FAR struct nsh_vtbl_s *vtbl, FAR const char *cmd,
    * applications.
    */
 
-  ret = exec_builtin(cmd, (FAR const char **)argv);
+  ret = exec_builtin(cmd, (FAR const char **)argv, redirfile, oflags);
   if (ret >= 0)
     {
       /* The application was successfully started (but still blocked because
@@ -191,7 +197,7 @@ int nsh_execapp(FAR struct nsh_vtbl_s *vtbl, FAR const char *cmd,
 #if !defined(CONFIG_SCHED_WAITPID) || !defined(CONFIG_NSH_DISABLEBG)
         {
           struct sched_param param;
-          sched_getparam(0, &param);
+          sched_getparam(ret, &param);
           nsh_output(vtbl, "%s [%d:%d]\n", cmd, ret, param.sched_priority);
 
           /* Backgrounded commands always 'succeed' as long as we can start
@@ -205,13 +211,13 @@ int nsh_execapp(FAR struct nsh_vtbl_s *vtbl, FAR const char *cmd,
 
   sched_unlock();
 
-  /* If exec_builtin() or waitpid() failed, then return the negated errno
+  /* If exec_builtin() or waitpid() failed, then return -1 (ERROR) with the
-   * value.
+   * errno value set appropriately.
    */
 
   if (ret < 0)
     {
-      return -errno;
+      return ERROR;
     }
 
   return ret;

nshlib/nsh_codeccmd.c

@@ -1,5 +1,5 @@
 /****************************************************************************
- * apps/nshlib/nsh_apps.c
+ * apps/nshlib/nsh_codeccmd.c
  *
  * This file is part of NuttX, contributed by Darcy Gong
  *

nshlib/nsh_parse.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * apps/nshlib/nsh_parse.c
  *
- *   Copyright (C) 2007-2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -723,15 +723,11 @@ static int cmd_exit(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
  * Name: nsh_execute
  *
  * Description:
- *   Exectue the command in argv[0]
+ *   Execute the command in argv[0]
  *
  * Returned Value:
- *   <0          If exec_builtin() fails, then the negated errno value
- *               is returned.
  *   -1 (ERRROR) if the command was unsuccessful
  *    0 (OK)     if the command was successful
- *    1          if an application task was spawned successfully, but
- *               returned failure exit status.
  *
  ****************************************************************************/
 
@@ -752,21 +748,6 @@ static int nsh_execute(FAR struct nsh_vtbl_s *vtbl, int argc, char *argv[])
 
   cmd = argv[0];
 
-  /* Try to find a command in the application library. */
-
-#ifdef CONFIG_NSH_BUILTIN_APPS
-  ret = nsh_execapp(vtbl, cmd, argv);
-
-  /* If the built-in application was successfully started, return OK 
-   * or 1 (if the application returned a non-zero exit status).
-   */
-
-  if (ret >= 0)
-    {
-      return ret;
-    }
-#endif
-
   /* See if the command is one that we understand */
 
   for (cmdmap = g_cmdmap; cmdmap->cmd; cmdmap++)
@@ -1410,6 +1391,47 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
         }
     }
 
+  /* Check if the maximum number of arguments was exceeded */
+
+  if (argc > CONFIG_NSH_MAXARGUMENTS)
+    {
+      nsh_output(vtbl, g_fmttoomanyargs, cmd);
+    }
+
+  /* Does this command correspond to a builtin command?
+   * nsh_builtin() returns:
+   *
+   *   -1 (ERROR)  if the application task corresponding to 'argv[0]' could not
+   *               be started (possibly because it doesn not exist).
+   *    0 (OK)     if the application task corresponding to 'argv[0]' was
+   *               and successfully started.  If CONFIG_SCHED_WAITPID is
+   *               defined, this return value also indicates that the
+   *               application returned successful status (EXIT_SUCCESS)
+   *    1          If CONFIG_SCHED_WAITPID is defined, then this return value
+   *               indicates that the application task was spawned successfully
+   *               but returned failure exit status.
+   *
+   * Note the priority if not effected by nice-ness.
+   */
+
+#ifdef CONFIG_NSH_BUILTIN_APPS
+  ret = nsh_builtin(vtbl, argv[0], argv, redirfile, oflags);
+  if (ret >= 0)
+    {
+      /* nsh_builtin() returned 0 or 1.  This means that the builtin
+       * command was successfully started (although it may not have ran
+       * successfully).  So certainly it is not an NSH command.
+       */
+
+      return nsh_saveresult(vtbl, ret != OK);
+    }
+
+  /* No, not a built in command (or, at least, we were unable to start a
+   * builtin command of that name).  Treat it like an NSH command.
+   */
+
+#endif
+
   /* Redirected output? */
 
   if (vtbl->np.np_redirect)
@@ -1431,23 +1453,13 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
         }
     }
 
-  /* Check if the maximum number of arguments was exceeded */
-
-  if (argc > CONFIG_NSH_MAXARGUMENTS)
-    {
-      nsh_output(vtbl, g_fmttoomanyargs, cmd);
-    }
-
   /* Handle the case where the command is executed in background.
    * However is app is to be started as builtin new process will
-   * be created anyway, so skip this step. */
+   * be created anyway, so skip this step.
+   */
 
 #ifndef CONFIG_NSH_DISABLEBG
-  if (vtbl->np.np_bg
+  if (vtbl->np.np_bg)
-#ifdef CONFIG_NSH_BUILTIN_APPS
-      && builtin_isavail(argv[0]) < 0     
-#endif
-  )
     {
       struct sched_param param;
       struct nsh_vtbl_s *bkgvtbl;
@@ -1514,6 +1526,7 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
                   priority = min_priority;
                 }
             }
+
           param.sched_priority = priority;
         }
 
@@ -1553,8 +1566,6 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
        *
        * -1 (ERRROR) if the command was unsuccessful
        *  0 (OK)     if the command was successful
-       *  1          if an application task was spawned successfully, but
-       *             returned failure exit status.
        */
 
       ret = nsh_execute(vtbl, argc, argv);
@@ -1568,11 +1579,11 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
           nsh_undirect(vtbl, save);
         }
 
-      /* Treat both errors and non-zero return codes as "errors" so that
+      /* Mark errors so that it is possible to test for non-zero return values
-       * it is possible to test for non-zero returns in nsh scripts.
+       * in nsh scripts.
        */
 
-      if (ret != OK)
+      if (ret < 0)
         {
           goto errout;
         }