nshlib/prompt: extend NSH prompt string management

Currently NSH prompt is defined at build time, thus improper for AMP cases
where the same NSH binary is used on different nodes as the same NSH prompt
shows on all nodes.

This patch attempts to support runtime prompt string population from ordered
sources:
  - the environment variable defined by NSH_PROMPT_ENV plus suffix
  - the NSH_PROMPT_STRING
  - the HOSTNAME plus suffix
The suffix is defined by NSH_PROMPT_SUFFIX so that to clearly separate the
command inputs.

Changes in `nshlib/`

- Kconfig:       add configs NSH_PROMPT_MAX/ENV/SUFFIX etc
- nsh.h:         adjust g_nshprompt defs, add nsh_update_prompt
- nsh_parse.c    relocate g_nshpromt to nsh_prompt.c
- nsh_init.c     revise to use nsh_update_prompt once
- nsh_session.c  revise to use methods in nsh_prompt.c
- Makefile       add nsh_prompt.c
- CMakeLists.txt add nsh_prompt.c

New additions in `nshlib/`

- nsh_prompt.c   prompt related data structures and methods.

Signed-off-by: Yanfeng Liu <yfliu2008@qq.com>

nshlib/CMakeLists.txt

@@ -37,6 +37,7 @@ if(CONFIG_NSH_LIBRARY)
     nsh_mmcmds.c
     nsh_timcmds.c
     nsh_envcmds.c
+    nsh_prompt.c
     nsh_syscmds.c
     nsh_dbgcmds.c)
 

nshlib/Kconfig

@@ -66,7 +66,31 @@ config NSH_PROMPT_STRING
 	string "Prompt String"
 	default "nsh> "
 	---help---
-		Provide the shell prompt string, default is "nsh> ".
+		Provide the shell prompt string with size limit NSH_PROMPT_MAX.
+		default is "nsh> ".
+
+config NSH_PROMPT_MAX
+	int "Maximum Size of Prompt String"
+	default NAME_MAX
+	---help---
+		The maximum size of shell prompt string, including ending null.
+
+config NSH_PROMPT_ENV
+	string "Prompt String Environment Variable"
+	default "PS1"
+	depends on !DISABLE_ENVIRON
+	---help---
+		The environment variable name containing prompt string.
+		Only used when NSH_PROMPT_STRING is empty.
+
+config NSH_PROMPT_SUFFIX
+	string "Suffix used to derive fallback prompt string"
+	default "> "
+	---help---
+		When NSH_PROMPT_STRING is empty, the environment variable defined
+		by NSH_PROMPT_ENV or hostname will be used to derive the prompt
+		at runtime. This suffix is a part of the final prompt that serves
+		to clearly separate prompt from user inputs.
 
 config NSH_DISABLE_ECHOBACK
 	bool "Disable echoback"

nshlib/Makefile

@@ -24,7 +24,7 @@ include $(APPDIR)/Make.defs
 
 CSRCS  = nsh_init.c nsh_parse.c nsh_console.c nsh_script.c nsh_system.c
 CSRCS += nsh_command.c nsh_fscmds.c nsh_ddcmd.c nsh_proccmds.c nsh_mmcmds.c
-CSRCS += nsh_timcmds.c nsh_envcmds.c nsh_syscmds.c nsh_dbgcmds.c
+CSRCS += nsh_timcmds.c nsh_envcmds.c nsh_syscmds.c nsh_dbgcmds.c nsh_prompt.c
 
 CSRCS += nsh_session.c
 ifeq ($(CONFIG_NSH_CONSOLE_LOGIN),y)

nshlib/nsh.h

@@ -748,7 +748,6 @@ extern const char g_loginsuccess[];
 extern const char g_badcredentials[];
 extern const char g_loginfailure[];
 #endif
-extern const char g_nshprompt[];
 extern const char g_fmtsyntax[];
 extern const char g_fmtargrequired[];
 extern const char g_fmtnomatching[];
@@ -825,6 +824,11 @@ int nsh_session(FAR struct console_stdio_s *pstate,
                 int login, int argc, FAR char *argv[]);
 int nsh_parse(FAR struct nsh_vtbl_s *vtbl, FAR char *cmdline);
 
+/* Prompt string handling */
+
+FAR const char *nsh_prompt(void);
+void nsh_update_prompt(void);
+
 /****************************************************************************
  * Name: nsh_login
  *

nshlib/nsh_init.c

@@ -110,10 +110,14 @@ void nsh_initialize(void)
   FAR struct console_stdio_s *pstate;
 #endif
 
-#if defined(CONFIG_NSH_READLINE) && defined(CONFIG_READLINE_TABCOMPLETION)
+  /* populate NSH prompt string */
-  /* Configure the NSH prompt */
 
-  readline_prompt(g_nshprompt);
+  nsh_update_prompt();
+
+#if defined(CONFIG_NSH_READLINE) && defined(CONFIG_READLINE_TABCOMPLETION)
+  /* Configure readline prompt */
+
+  readline_prompt(nsh_prompt());
 
 #  ifdef CONFIG_READLINE_HAVE_EXTMATCH
   /* Set up for tab completion on NSH commands */

nshlib/nsh_parse.c

@@ -321,10 +321,6 @@ const char g_badcredentials[]    = "\nInvalid username or password\n";
 const char g_loginfailure[]      = "Login failed!\n";
 #endif
 
-/* The NSH prompt */
-
-const char g_nshprompt[]         = CONFIG_NSH_PROMPT_STRING;
-
 /* Common, message formats */
 
 const char g_fmtsyntax[]         = "nsh: %s: syntax error\n";

nshlib/nsh_prompt.c

@@ -0,0 +1,105 @@
+/****************************************************************************
+ * apps/nshlib/nsh_prompt.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#include "nsh.h"
+
+/****************************************************************************
+ * Preprocessor Macros
+ ****************************************************************************/
+
+#define NSH_PROMPT_SIZE      (CONFIG_NSH_PROMPT_MAX + 1 - \
+                              sizeof(CONFIG_NSH_PROMPT_SUFFIX))
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+static char g_nshprompt[CONFIG_NSH_PROMPT_MAX] = CONFIG_NSH_PROMPT_STRING;
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: nsh_update_prompt
+ *
+ * Description:
+ *   This updates g_nshprompt from multiple sources, in the following order:
+ *
+ *   - non-empty NSH_PROMPT_ENV variable and suffix
+ *   - non-empty NSH_PROMPT_STRING
+ *   - non-empty HOSTNAME and suffix
+ *
+ * Note that suffix has higher priority when used to help clearly separate
+ * prompts from command line inputs.
+ *
+ * Results:
+ *   - updated g_nsh_prompt value.
+ *
+ ****************************************************************************/
+
+void nsh_update_prompt(void)
+{
+  static_assert(CONFIG_NSH_PROMPT_MAX > sizeof(CONFIG_NSH_PROMPT_STRING),
+                                          "NSH_PROMPT_STRING too long!");
+  static_assert(CONFIG_NSH_PROMPT_MAX > sizeof(CONFIG_NSH_PROMPT_SUFFIX),
+                                          "NSH_PROMPT_SUFFIX too long!");
+  #ifndef CONFIG_DISABLE_ENVIRON
+  if (getenv(CONFIG_NSH_PROMPT_ENV))
+    {
+      strlcpy(g_nshprompt, getenv(CONFIG_NSH_PROMPT_ENV), NSH_PROMPT_SIZE);
+      strcat(g_nshprompt, CONFIG_NSH_PROMPT_SUFFIX);
+    }
+  else
+  #endif
+  if (CONFIG_NSH_PROMPT_STRING[0])
+    {
+      strcpy(g_nshprompt, CONFIG_NSH_PROMPT_STRING);
+    }
+  else
+    {
+      gethostname(g_nshprompt, NSH_PROMPT_SIZE);
+      strcat(g_nshprompt, CONFIG_NSH_PROMPT_SUFFIX);
+    }
+}
+
+/****************************************************************************
+ * Name: nsh_prompt
+ *
+ * Description:
+ *   This function returns latest prompt string.
+ *   It is needed as g_nshprompt is no longer public.
+ *
+ ****************************************************************************/
+
+FAR const char *nsh_prompt(void)
+{
+  return g_nshprompt;
+}

nshlib/nsh_session.c

@@ -207,7 +207,7 @@ int nsh_session(FAR struct console_stdio_s *pstate,
        * occurs. Either  will cause the session to terminate.
        */
 
-      ret = cle_fd(pstate->cn_line, g_nshprompt, CONFIG_NSH_LINELEN,
+      ret = cle_fd(pstate->cn_line, nsh_prompt(), CONFIG_NSH_LINELEN,
                    INFD(pstate), OUTFD(pstate));
       if (ret < 0)
         {
@@ -218,7 +218,7 @@ int nsh_session(FAR struct console_stdio_s *pstate,
 #else
       /* Display the prompt string */
 
-      write(OUTFD(pstate), g_nshprompt, strlen(g_nshprompt));
+      write(OUTFD(pstate), nsh_prompt(), strlen(nsh_prompt()));
 
       /* readline() normally returns the number of characters read, but
        * will return EOF on end of file or if an error occurs.  EOF
@@ -243,6 +243,7 @@ int nsh_session(FAR struct console_stdio_s *pstate,
       /* Parse process the command */
 
       nsh_parse(vtbl, pstate->cn_line);
+      nsh_update_prompt();
     }
 
   return ret;