/core/src/aos_shell.c - Annotate - AMiRo-OS - Research for Cognitive Interaction

amiro-os / core / src / aos_shell.c @ 27d0378b

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-            e545e620
+/*
 AMiRo-OS is an operating system designed for the Autonomous Mini Robot (AMiRo) platform.
 Copyright (C) 2016..2018  Thomas Schöpping et al.
 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/>.
 */
-ca3
+/**
  * @file    aos_shell.c
  * @brief   Shell code.
  * @details Shell code as well as shell related channels and streams.
+ *
  * @addtogroup aos_shell
  * @{
  */
-            e545e620
+#include <aos_shell.h>
-            ba516b61
+#if (AMIROOS_CFG_SHELL_ENABLE == true)
-            e545e620
+#include <aos_debug.h>
 #include <aos_time.h>
 #include <aos_system.h>
 #include <string.h>
-            ba516b61
+            Thomas Schöpping
 /**
  * @brief   Event mask to be set on OS related events.
  */
 #define AOS_SHELL_EVENTMASK_OS                  EVENT_MASK(0)
 /**
  * @brief   Event mask to be set on a input event.
  */
 #define AOS_SHELL_EVENTMASK_INPUT               EVENT_MASK(1)
 /**
  * @brief   Implementation of the BaseAsynchronous write() method (inherited from BaseSequentialStream).
  */
 static size_t _channelwrite(void *instance, const uint8_t *bp, size_t n)
+{
   if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_OUTPUT_ENABLED) {
-            dd8738ea
+    return streamWrite(((AosShellChannel*)instance)->asyncchannel, bp, n);
-            ba516b61
+  } else {
     return 0;
+  }
+}
 /**
  * @brief   Implementation of the BaseAsynchronous read() method (inherited from BaseSequentialStream).
  */
 static size_t _channelread(void *instance, uint8_t *bp, size_t n)
+{
-            dd8738ea
+  if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_INPUT_ENABLED) {
     return streamRead(((AosShellChannel*)instance)->asyncchannel, bp, n);
   } else {
     return 0;
+  }
-            ba516b61
+            Thomas Schöpping
 /**
  * @brief   Implementation of the BaseAsynchronous put() method (inherited from BaseSequentialStream).
  */
 static msg_t _channelput(void *instance, uint8_t b)
+{
   if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_OUTPUT_ENABLED) {
-            dd8738ea
+    return streamPut(((AosShellChannel*)instance)->asyncchannel, b);
-            ba516b61
+  } else {
     return MSG_RESET;
+  }
+}
 /**
  * @brief   Implementation of the BaseAsynchronous get() method (inherited from BaseSequentialStream).
  */
 static msg_t _channelget(void *instance)
+{
-            dd8738ea
+  if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_INPUT_ENABLED) {
     return streamGet(((AosShellChannel*)instance)->asyncchannel);
   } else {
     return MSG_RESET;
+  }
-            ba516b61
+            Thomas Schöpping
 /**
  * @brief   Implementation of the BaseAsynchronous putt() method.
  */
-c99037f
+static msg_t _channelputt(void *instance, uint8_t b, sysinterval_t time)
-            ba516b61
+            Thomas Schöpping
   if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_OUTPUT_ENABLED) {
-            dd8738ea
+    return chnPutTimeout(((AosShellChannel*)instance)->asyncchannel, b, time);
-            ba516b61
+  } else {
     return MSG_RESET;
+  }
+}
 /**
  * @brief   Implementation of the BaseAsynchronous gett() method.
  */
-c99037f
+static msg_t _channelgett(void *instance, sysinterval_t time)
-            ba516b61
+            Thomas Schöpping
-            dd8738ea
+  if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_INPUT_ENABLED) {
     return chnGetTimeout(((AosShellChannel*)instance)->asyncchannel, time);
   } else {
     return MSG_RESET;
+  }
-            ba516b61
+            Thomas Schöpping
 /**
  * @brief   Implementation of the BaseAsynchronous writet() method.
  */
-c99037f
+static size_t _channelwritet(void *instance, const uint8_t *bp, size_t n, sysinterval_t time)
-            ba516b61
+            Thomas Schöpping
   if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_OUTPUT_ENABLED) {
-            dd8738ea
+    return chnWriteTimeout(((AosShellChannel*)instance)->asyncchannel, bp, n, time);
-            ba516b61
+  } else {
     return 0;
+  }
+}
 /**
  * @brief   Implementation of the BaseAsynchronous readt() method.
  */
-c99037f
+static size_t _channelreadt(void *instance, uint8_t *bp, size_t n, sysinterval_t time)
-            ba516b61
+            Thomas Schöpping
-            dd8738ea
+  if (((AosShellChannel*)instance)->flags & AOS_SHELLCHANNEL_INPUT_ENABLED) {
     return chnReadTimeout(((AosShellChannel*)instance)->asyncchannel, bp, n, time);
   } else {
     return 0;
+  }
-            ba516b61
+            Thomas Schöpping
-c99037f
+/**
  * @brief   Implementation of the BaseAsynchronousChannel ctl() method.
  */
 static msg_t _channelctl(void *instance, unsigned int operation, void *arg) {
   (void) instance;
   switch (operation) {
   case CHN_CTL_NOP:
     osalDbgCheck(arg == NULL);
     break;
   case CHN_CTL_INVALID:
     osalDbgAssert(false, "invalid CTL operation");
     break;
   default:
     break;
+  }
   return MSG_OK;
+}
-            ba516b61
+static const struct AosShellChannelVMT _channelvmt = {
-be0f
+  (size_t) 0,
-            ba516b61
+  _channelwrite,
   _channelread,
   _channelput,
   _channelget,
   _channelputt,
   _channelgett,
   _channelwritet,
   _channelreadt,
-c99037f
+  _channelctl,
-            ba516b61
+};
 static size_t _streamwrite(void *instance, const uint8_t *bp, size_t n)
+{
   aosDbgCheck(instance != NULL);
   // local variables
   AosShellChannel* channel = ((AosShellStream*)instance)->channel;
   size_t bytes;
   size_t maxbytes = 0;
   // iterate through the list of channels
   while (channel != NULL) {
     bytes = streamWrite(channel, bp, n);
     maxbytes = (bytes > maxbytes) ? bytes : maxbytes;
     channel = channel->next;
+  }
   return maxbytes;
+}
 static size_t _stremread(void *instance, uint8_t *bp, size_t n)
+{
   (void)instance;
   (void)bp;
   (void)n;
   return 0;
+}
 static msg_t _streamput(void *instance, uint8_t b)
+{
   aosDbgCheck(instance != NULL);
   // local variables
   AosShellChannel* channel = ((AosShellStream*)instance)->channel;
-            dd8738ea
+  msg_t ret = MSG_OK;
-            ba516b61
+            Thomas Schöpping
   // iterate through the list of channels
   while (channel != NULL) {
-            dd8738ea
+    msg_t ret_ = streamPut(channel, b);
     ret = (ret_ < ret) ? ret_ : ret;
-            ba516b61
+    channel = channel->next;
+  }
-            dd8738ea
+  return ret;
-            ba516b61
+            Thomas Schöpping
 static msg_t _streamget(void *instance)
+{
   (void)instance;
   return 0;
+}
 static const struct AosShellStreamVMT _streamvmt = {
-be0f
+  (size_t) 0,
-            ba516b61
+  _streamwrite,
   _stremread,
   _streamput,
   _streamget,
 };
-            e545e620
+/**
  * @brief   Enumerator of special keyboard keys.
  */
 typedef enum special_key {
   KEY_UNKNOWN,      /**< any/unknow key */
   KEY_AMBIGUOUS,    /**< key is ambiguous */
   KEY_TAB,          /**< tabulator key */
   KEY_ESCAPE,       /**< escape key */
   KEY_BACKSPACE,    /**< backspace key */
   KEY_INSERT,       /**< insert key */
   KEY_DELETE,       /**< delete key */
   KEY_HOME,         /**< home key */
   KEY_END,          /**< end key */
   KEY_PAGE_UP,      /**< page up key */
   KEY_PAGE_DOWN,    /**< page down key */
   KEY_ARROW_UP,     /**< arrow up key */
   KEY_ARROW_DOWN,   /**< arrow down key */
   KEY_ARROW_LEFT,   /**< arrow left key */
   KEY_ARROW_RIGHT,  /**< arrow right key */
 } special_key_t;
 /**
  * @brief   Enumerator for case (in)sensitive character matching.
  */
 typedef enum charmatch {
   CHAR_MATCH_NOT    = 0,  /**< Characters do not match at all. */
   CHAR_MATCH_NCASE  = 1,  /**< Characters would match case insensitive. */
   CHAR_MATCH_CASE   = 2,  /**< Characters do match with case. */
 } charmatch_t;
 /**
  * @brief   Print the shell prompt
  * @details Depending on the configuration flags, the system uptime is printed before the prompt string.
+ *
  * @param[in] shell   Pointer to the shell object.
  */
 static void _printPrompt(aos_shell_t* shell)
+{
-d0378b
+/** commented out by simon welzel
-            e545e620
+  aosDbgCheck(shell != NULL);
-aeae
+  // print some time informattion before prompt if configured
   if (shell->config & (AOS_SHELL_CONFIG_PROMPT_UPTIME | AOS_SHELL_CONFIG_PROMPT_DATETIME)) {
     // printf the system uptime
     if ((shell->config & (AOS_SHELL_CONFIG_PROMPT_UPTIME | AOS_SHELL_CONFIG_PROMPT_DATETIME)) == AOS_SHELL_CONFIG_PROMPT_UPTIME) {
       // get current system uptime
       aos_timestamp_t uptime;
       aosSysGetUptime(&uptime);
       chprintf((BaseSequentialStream*)&shell->stream, "[%01u:%02u:%02u:%02u:%03u:%03u] ",
                (uint32_t)(uptime / MICROSECONDS_PER_DAY),
                (uint8_t)(uptime % MICROSECONDS_PER_DAY / MICROSECONDS_PER_HOUR),
                (uint8_t)(uptime % MICROSECONDS_PER_HOUR / MICROSECONDS_PER_MINUTE),
                (uint8_t)(uptime % MICROSECONDS_PER_MINUTE / MICROSECONDS_PER_SECOND),
                (uint16_t)(uptime % MICROSECONDS_PER_SECOND / MICROSECONDS_PER_MILLISECOND),
                (uint16_t)(uptime % MICROSECONDS_PER_MILLISECOND / MICROSECONDS_PER_MICROSECOND));
+    }
     else if ((shell->config & (AOS_SHELL_CONFIG_PROMPT_UPTIME | AOS_SHELL_CONFIG_PROMPT_DATETIME)) == AOS_SHELL_CONFIG_PROMPT_DATETIME) {
       // get current RTC time
       struct tm dt;
       aosSysGetDateTime(&dt);
       chprintf((BaseSequentialStream*)&shell->stream, "[%02u-%02u-%04u|%02u:%02u:%02u] ",
                dt.tm_mday,
                dt.tm_mon + 1,
                dt.tm_year + 1900,
                dt.tm_hour,
                dt.tm_min,
                dt.tm_sec);
+    }
     else {
       aosDbgAssert(false);
+    }
-            e545e620
+            Thomas Schöpping
   // print the actual prompt string
   if (shell->prompt && !(shell->config & AOS_SHELL_CONFIG_PROMPT_MINIMAL)) {
-            ba516b61
+    chprintf((BaseSequentialStream*)&shell->stream, "%s$ ", shell->prompt);
-            e545e620
+  } else {
-            ba516b61
+    chprintf((BaseSequentialStream*)&shell->stream, "%>$ ");
-            e545e620
+            Thomas Schöpping
-d0378b
+*/
-            e545e620
+  return;
+}
 /**
  * @brief   Interprete a escape sequence
+ *
  * @param[in] seq   Character sequence to interprete.
  *                  Must be terminated by NUL byte.
+ *
  * @return          A @p special_key value.
  */
 static special_key_t _interpreteEscapeSequence(const char seq[])
+{
   // local variables
   bool ambiguous = false;
   int cmp = 0;
   // TAB
   /* not supported yet; use "\x09" instead */
   // BACKSPACE
   /* not supported yet; use "\x08" instead */
   // ESCAPE
   cmp = strcmp(seq, "\x1B");
   if (cmp == 0) {
     return KEY_ESCAPE;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // INSERT
   cmp = strcmp(seq, "\x1B\x5B\x32\x7E");
   if (cmp == 0) {
     return KEY_INSERT;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // DELETE
   cmp = strcmp(seq, "\x1B\x5B\x33\x7E");
   if (cmp == 0) {
     return KEY_DELETE;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // HOME
   cmp = strcmp(seq, "\x1B\x4F\x48");
   if (cmp == 0) {
     return KEY_HOME;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // END
   cmp = strcmp(seq, "\x1B\x4F\x46");
   if (cmp == 0) {
     return KEY_END;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // PAGE UP
   cmp = strcmp(seq, "\x1B\x5B\x35\x7E");
   if (cmp == 0) {
     return KEY_PAGE_UP;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // PAGE DOWN
   cmp = strcmp(seq, "\x1B\x5B\x36\x7E");
   if (cmp == 0) {
     return KEY_PAGE_DOWN;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // ARROW UP
   cmp = strcmp(seq, "\x1B\x5B\x41");
   if (cmp == 0) {
     return KEY_ARROW_UP;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // ARROW DOWN
   cmp = strcmp(seq, "\x1B\x5B\x42");
   if (cmp == 0) {
     return KEY_ARROW_DOWN;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // ARROW LEFT
   cmp = strcmp(seq, "\x1B\x5B\x44");
   if (cmp == 0) {
     return KEY_ARROW_LEFT;
   } else {
     ambiguous |= (cmp < 0);
+  }
   // ARROW RIGHT
   cmp = strcmp(seq, "\x1B\x5B\x43");
   if (cmp == 0) {
     return KEY_ARROW_RIGHT;
   } else {
     ambiguous |= (cmp < 0);
+  }
   return ambiguous ? KEY_AMBIGUOUS : KEY_UNKNOWN;
+}
 /**
  * @brief   Move the cursor in the terminal
+ *
  * @param[in] shell   Pointer to the shell object.
  * @param[in] from    Starting position of the cursor.
  * @param[in] to      Target position to move the cursor to.
+ *
  * @return            The number of positions moved.
  */
 static int _moveCursor(aos_shell_t* shell, const size_t from, const size_t to)
+{
   aosDbgCheck(shell != NULL);
   // local variables
   size_t pos = from;
   // move cursor left by printing backspaces
   while (pos > to) {
-            ba516b61
+    streamPut(&shell->stream, '\b');
-            e545e620
+    --pos;
+  }
   // move cursor right by printing line content
   while (pos < to) {
-            ba516b61
+    streamPut(&shell->stream, shell->line[pos]);
-            e545e620
+    ++pos;
+  }
   return (int)pos - (int)from;
+}
 /**
  * @brief   Print content of the shell line
+ *
  * @param[in] shell   Pointer to the shell object.
  * @param[in] from    First position to start printing from.
  * @param[in] to      Position after the last character to print.
+ *
  * @return            Number of characters printed.
  */
 static inline size_t _printLine(aos_shell_t* shell, const size_t from, const size_t to)
+{
   aosDbgCheck(shell != NULL);
   // local variables
   size_t cnt;
   for (cnt = 0; from + cnt < to; ++cnt) {
-            ba516b61
+    streamPut(&shell->stream, shell->line[from + cnt]);
-            e545e620
+            Thomas Schöpping
   return cnt;
+}
 /**
  * @brief   Compare two characters.
+ *
  * @param[in] lhs       First character to compare.
  * @param[in] rhs       Second character to compare.
+ *
  * @return              How well the characters match.
  */
 static inline charmatch_t _charcmp(char lhs, char rhs)
+{
   // if lhs is a upper case letter and rhs is a lower case letter
   if (lhs >= 'A' && lhs <= 'Z' && rhs >= 'a' && rhs <= 'z') {
     return (lhs == (rhs - 'a' + 'A')) ? CHAR_MATCH_NCASE : CHAR_MATCH_NOT;
+  }
   // if lhs is a lower case letter and rhs is a upper case letter
   else if (lhs >= 'a' && lhs <= 'z' && rhs >= 'A' && rhs <= 'Z') {
     return ((lhs - 'a' + 'A') == rhs) ? CHAR_MATCH_NCASE : CHAR_MATCH_NOT;
+  }
   // default
   else {
     return (lhs == rhs) ? CHAR_MATCH_CASE : CHAR_MATCH_NOT;
+  }
+}
 /**
  * @brief   Maps an character from ASCII to a modified custom encoding.
  * @details The custom character encoding is very similar to ASCII and has the following structure:
  *          0x00=NULL ... 0x40='@' (identically to ASCII)
  *          0x4A='a'; 0x4B='A'; 0x4C='b'; 0x4D='B' ... 0x73='z'; 0x74='Z' (custom letter order)
  *          0x75='[' ... 0x7A='`' (0x5B..0x60 is ASCII)
  *          0x7B='{' ... 0x7F=DEL (identically to ASCII)
+ *
  * @param[in] c   Character to map to the custom encoding.
+ *
  * @return    The customly encoded character.
  */
 static inline char _mapAscii2Custom(const char c)
+{
   if (c >= 'A' && c <= 'Z') {
     return ((c - 'A') * 2) + 'A' + 1;
   } else if (c > 'Z' && c < 'a') {
     return c + ('z' - 'a') + 1;
   } else if (c >= 'a' && c <= 'z') {
     return ((c - 'a') * 2) + 'A';
   } else {
     return c;
+  }
+}
 /**
  * @brief   Compares two strings wrt letter case.
  * @details Comparisson uses a custom character encoding or mapping.
  *          See @p _mapAscii2Custom for details.
+ *
  * @param[in] str1    First string to compare.
  * @param[in] str2    Second string to compare.
  * @param[in] cs      Flag indicating whether comparison shall be case sensitive.
  * @param[in,out] n   Maximum number of character to compare (in) and number of matching characters (out).
  *                    If a null pointer is specified, this parameter is ignored.
  *                    If the value pointed to is zero, comarison will not be limited.
  * @param[out] m      Optional indicator whether there was at least one case mismatch.
+ *
  * @return      Integer value indicating the relationship between the strings.
  * @retval <0   The first character that does not match has a lower value in str1 than in str2.
  * @retval  0   The contents of both strings are equal.
  * @retval >0   The first character that does not match has a greater value in str1 than in str2.
  */
 static int _strccmp(const char *str1, const char *str2, bool cs, size_t* n, charmatch_t* m)
+{
   aosDbgCheck(str1 != NULL);
   aosDbgCheck(str2 != NULL);
   // initialize variables
   if (m) {
     *m = CHAR_MATCH_NOT;
+  }
   size_t i = 0;
   // iterate through the strings
   while ((n == NULL) || (*n == 0) || (*n > 0 && i < *n)) {
     // break on NUL
     if (str1[i] == '\0' || str2[i] == '\0') {
       if (n) {
         *n = i;
+      }
       break;
+    }
     // compare character
     const charmatch_t match = _charcmp(str1[i], str2[i]);
     if ((match == CHAR_MATCH_CASE) || (!cs && match == CHAR_MATCH_NCASE)) {
       if (m != NULL && *m != CHAR_MATCH_NCASE) {
         *m = match;
+      }
       ++i;
     } else {
       if (n) {
         *n = i;
+      }
       break;
+    }
+  }
   return _mapAscii2Custom(str1[i]) - _mapAscii2Custom(str2[i]);
+}
-            ba516b61
+static aos_status_t _readChannel(aos_shell_t* shell, AosShellChannel* channel, size_t* n)
-            e545e620
+            Thomas Schöpping
   aosDbgCheck(shell != NULL);
-            ba516b61
+  aosDbgCheck(channel != NULL);
   aosDbgCheck(n != NULL);
-            e545e620
+            Thomas Schöpping
   // local variables
-            ba516b61
+  aos_shellaction_t action = AOS_SHELL_ACTION_NONE;
-            e545e620
+  char c;
-            dd8738ea
+  special_key_t key;
-            e545e620
+            Thomas Schöpping
-            ba516b61
+  // initialize output variables
   *n = 0;
   // read character by character from the channel
   while (chnReadTimeout(channel, (uint8_t*)&c, 1, TIME_IMMEDIATE)) {
-            dd8738ea
+    key = KEY_UNKNOWN;
-            e545e620
+            Thomas Schöpping
     // parse escape sequence
-            ba516b61
+    if (shell->inputdata.escp > 0) {
       shell->inputdata.escseq[shell->inputdata.escp] = c;
       ++shell->inputdata.escp;
       key = _interpreteEscapeSequence(shell->inputdata.escseq);
-            e545e620
+      if (key == KEY_AMBIGUOUS) {
         // read next byte to resolve ambiguity
         continue;
       } else {
-            ba516b61
+        /*
          * If the escape sequence could either be parsed sucessfully
          * or there is no match (KEY_UNKNOWN),
          * reset the sequence variable and interprete key/character
          */
         shell->inputdata.escp = 0;
         memset(shell->inputdata.escseq, '\0', sizeof(shell->inputdata.escseq)*sizeof(shell->inputdata.escseq[0]));
-            e545e620
+            Thomas Schöpping
+    }
-            ba516b61
+    /* interprete keys or character */
-            e545e620
+            Thomas Schöpping
-            ba516b61
+      // default
       action = AOS_SHELL_ACTION_NONE;
       // printable character
       if (key == KEY_UNKNOWN && c >= '\x20' && c <= '\x7E') {
         action = AOS_SHELL_ACTION_READCHAR;
+      }
       // tab key or character
       else if (key == KEY_TAB || c == '\x09') {
         /*
          * pressing tab once applies auto fill
          * pressing tab a second time prints suggestions
          */
         if (shell->inputdata.lastaction == AOS_SHELL_ACTION_AUTOFILL || shell->inputdata.lastaction == AOS_SHELL_ACTION_SUGGEST) {
           action = AOS_SHELL_ACTION_SUGGEST;
-            e545e620
+        } else {
-            ba516b61
+          action = AOS_SHELL_ACTION_AUTOFILL;
-            e545e620
+            Thomas Schöpping
-            ba516b61
+            Thomas Schöpping
       // INS key
       else if (key == KEY_INSERT) {
         action = AOS_SHELL_ACTION_INSERTTOGGLE;
+      }
       // DEL key or character
       else if (key == KEY_DELETE || c == '\x7F') {
         // ignore if cursor is at very right
         if (shell->inputdata.cursorpos < shell->inputdata.lineend) {
           action = AOS_SHELL_ACTION_DELETEFORWARD;
-            e545e620
+            Thomas Schöpping
-            ba516b61
+            Thomas Schöpping
       // backspace key or character
       else if (key == KEY_BACKSPACE || c == '\x08') {
         // ignore if cursor is at very left
         if (shell->inputdata.cursorpos > 0) {
           action = AOS_SHELL_ACTION_DELETEBACKWARD;
-            e545e620
+            Thomas Schöpping
-            ba516b61
+            Thomas Schöpping
       // 'page up' of 'arrow up' key
       else if (key == KEY_PAGE_UP || key == KEY_ARROW_UP) {
-            e545e620
+        // ignore if there was some input
-            ba516b61
+        if (shell->inputdata.noinput) {
           action = AOS_SHELL_ACTION_RECALLLAST;
-            e545e620
+            Thomas Schöpping
-            ba516b61
+            Thomas Schöpping
       // 'page down' key, 'arrow done' key, 'end of test' character or 'end of transmission' character
       else if (key == KEY_PAGE_DOWN || key == KEY_ARROW_DOWN || c == '\x03' || c == '\x03') {
-            e545e620
+        // ignore if line is empty
-            ba516b61
+        if (shell->inputdata.lineend > 0) {
           action = AOS_SHELL_ACTION_CLEAR;
-            e545e620
+            Thomas Schöpping
-            ba516b61
+            Thomas Schöpping
       // 'home' key