Code Cleanup + Ctrl+D fix + Ctrl+L clears screen

- Removed some code duplication
- Ctrl+D is fixed and now works as it should (exit if user didn't
write anything, ignore otherwise)
- Ctrl+L clears the terminal screen

main.c

@@ -48,10 +48,11 @@ void* ccalloc(size_t size, size_t n)
 }
 
 static constexpr size_t max_line = 1024;
-static char string_buffer[max_line];
+
 char* __readline_file(FILE* stream)
 {
-  if(fgets(string_buffer, max_line, stream) == NULL)
+  static char buffer[max_line];
+  if(fgets(buffer, sizeof(buffer), stream) == NULL)
   {
     if(ferror(stream))
     {
@@ -62,13 +63,13 @@ char* __readline_file(FILE* stream)
     return NULL;
   }
   
-  size_t length = strlen(string_buffer);
+  size_t length = strlen(buffer);
   //Remove trailing \n
-  if (length > 0 && string_buffer[length - 1] == '\n')
+  if (length > 0 && buffer[length - 1] == '\n')
   {
-    string_buffer[length - 1] = '\0';
+    buffer[length - 1] = '\0';
   }
-  return string_buffer;
+  return buffer;
 }
 
 static struct termios orig_termios;
@@ -139,24 +140,9 @@ size_t utf8_display_width(const char *buf, size_t len)
 
   while (i < len) {
     unsigned char c = buf[i];
-
-    if ((c & 0x80) == 0) {
-      i += 1;
+    i += utf8_char_len(c);
     width += 1;
   }
-    else if ((c & 0xE0) == 0xC0) {
-      i += 2;
-      width += 1;
-    }
-    else if ((c & 0xF0) == 0xE0) {
-      i += 3;
-      width += 1;
-    }
-    else {
-      i += 4;
-      width += 1;
-    }
-  }
 
   return width;
 }
@@ -180,24 +166,9 @@ size_t visible_width(const char *s)
     }
 
     unsigned char c = s[i];
-
-    if ((c & 0x80) == 0) {
-      i += 1;
+    i += utf8_char_len(c);
     width += 1;
   }
-    else if ((c & 0xE0) == 0xC0) {
-      i += 2;
-      width += 1;
-    }
-    else if ((c & 0xF0) == 0xE0) {
-      i += 3;
-      width += 1;
-    }
-    else {
-      i += 4;
-      width += 1;
-    }
-  }
 
   return width;
 }
@@ -205,7 +176,7 @@ size_t visible_width(const char *s)
 char* __readline_interactive(char* prompt)
 {
   enable_raw_mode();
-  static char buffer[max_length];
+  static char buffer[max_line];
   size_t cursor = 0;
   size_t len = 0;
   ssize_t swrite(int fd, const char* str)
@@ -282,6 +253,19 @@ char* __readline_interactive(char* prompt)
 	}
       }
     }
+    else if (utf8[0] == 0x04) //CTRL + D
+    {
+      if(len == 0)
+      {
+	disable_raw_mode();
+	return NULL;
+      }
+    }
+    else if (utf8[0] == 0x0C) //CTRL + L
+    {
+      swrite(1, "\x1b[2J"); // clear screen
+      swrite(1, "\x1b[H");  // cursor home
+    }
     else {
       if(len < sizeof(buffer))
       {
@@ -866,7 +850,7 @@ int execute_pipeline(struct pipeline* pl, int capture, char** out)
       
       if(strcmp(cmd_name, "cd") == 0)
       {
-	char* path = cmd->argv[1] ? cmd->argv[1] : getenv("HOME");
+	char* path = cmd->argv[1] ? cmd->argv[1] : get_home();
 	if (cd(path) < 0)
 	{
 	  char err_buf[max_length] = {0};
@@ -923,43 +907,43 @@ int execute_pipeline(struct pipeline* pl, int capture, char** out)
     return WEXITSTATUS(status);
 }
 
-char username_buf[max_env_var_length] = {0};
 char* get_user()
 {
+  static char buf[max_env_var_length] = {0};
   char* result = getenv("USER");
   if(!result)
   {
     return "UNKNOWN";
   }
-  size_t length = min_size_t(sizeof(username_buf), strlen(result) + 1);
-  memcpy(username_buf, result, length);
-  return username_buf;
+  size_t length = min_size_t(sizeof(buf), strlen(result) + 1);
+  memcpy(buf, result, length);
+  return buf;
 }
 
-char home_buf[max_length] = {0};
 char* get_home()
 {
+  static char buf[max_length] = {0};
   char* result = getenv("HOME");
   if(!result)
   {
     return "UNKNOWN_HOME_PATH";
   }
-  size_t length = min_size_t(sizeof(home_buf), strlen(result) + 1);
-  memcpy(home_buf, result, length);
-  return home_buf;
+  size_t length = min_size_t(sizeof(buf), strlen(result) + 1);
+  memcpy(buf, result, length);
+  return buf;
 }
 
-char pwd_buf[max_length] = {0};
 char* get_pwd()
 {
+  static char buf[max_length] = {0};
   char* result = getenv("PWD");
   if(!result)
   {
     return "UNKNOWN";
   }
-  size_t length = min_size_t(sizeof(pwd_buf), strlen(result) + 1);
-  memcpy(pwd_buf, result, length);
-  return pwd_buf;
+  size_t length = min_size_t(sizeof(buf), strlen(result) + 1);
+  memcpy(buf, result, length);
+  return buf;
 }
 
 char* prettify_pwd(char* pwd)
@@ -988,9 +972,9 @@ char* prettify_pwd(char* pwd)
   return pwd;
 }
 
-char prompt_buf[max_length] = {0};
 char* generate_ps1_prompt()
 {
+  static char prompt_buf[max_length] = {0};
   char env_buf[max_env_var_length] = {0};
   char* ps1 = getenv("PS1");
   if(!ps1)