libc/stdout: add an option to redirect standard output stream to syslog

Redirect standard output stream of printf(), vprintf(), puts(), putchar() to syslog,
This option will ensure the printing sequence of syslog/printf to avoid
confusion. Noted that if enable this option, the redirection
capability of standard input(<) and output(>) will not be work as expect in
(nsh)nuttx shell.

Signed-off-by: chao an <[email protected]>

Author: anchao

drivers/syslog/Kconfig

@@ -407,5 +407,25 @@ config SYSLOG_REGISTER
 	---help---
 		This option will support register the syslog channel dynamically.
 
+config SYSLOG_STDOUT
+	bool "Redirect standard output stream of printf() and vprintf() to syslog"
+	default n
+	---help---
+		Redirect standard output stream of printf(), vprintf(), puts(), putchar() to syslog,
+		This option will ensure the printing sequence of syslog/printf to avoid
+		confusion. Noted that if enable this option, the redirection
+		capability of standard input(<) and output(>) will not be work as expect in
+		(nsh)nuttx shell.
+
+if SYSLOG_STDOUT
+
+config SYSLOG_STDOUT_PREFIX
+	bool "Redirect standard output stream with syslog prefix"
+	default n
+	---help---
+		Redirect standard output stream with syslog prefix.
+
+endif # SYSLOG_STDOUT
+
 endif # SYSLOG
 endmenu # System logging

libs/libc/stdio/lib_printf.c

@@ -25,6 +25,10 @@
  ****************************************************************************/
 
 #include <stdio.h>
+#include <syslog.h>
+
+#include <nuttx/streams.h>
+#include <nuttx/syslog/syslog.h>
 
 /****************************************************************************
  * Public Functions
@@ -40,7 +44,25 @@ int printf(FAR const IPTR char *fmt, ...)
   int     ret;
 
   va_start(ap, fmt);
-#ifdef CONFIG_FILE_STREAM
+
+#ifdef CONFIG_SYSLOG_STDOUT_PREFIX
+  ret = nx_vsyslog(LOG_NOTICE, fmt, &ap);
+#elif defined(CONFIG_SYSLOG_STDOUT)
+  struct lib_syslograwstream_s stream;
+
+  /* Wrap the low-level output in a stream object and let lib_vsprintf
+   * do the work.
+   */
+
+  lib_syslograwstream_open(&stream);
+
+  ret = lib_vsprintf_internal(&stream.common, fmt, ap);
+
+  /* Flush and destroy the syslog stream buffer */
+
+  lib_syslograwstream_close(&stream);
+
+#elif defined(CONFIG_FILE_STREAM)
   ret = vfprintf(stdout, fmt, ap);
 #else
   ret = vdprintf(STDOUT_FILENO, fmt, ap);

libs/libc/stdio/lib_putchar.c

@@ -33,7 +33,9 @@
 
 int putchar(int c)
 {
-#ifdef CONFIG_FILE_STREAM
+#ifdef CONFIG_SYSLOG_STDOUT
+  return printf("%c", c);
+#elif defined(CONFIG_FILE_STREAM)
   return fputc(c, stdout);
 #else
   unsigned char tmp = c;
@@ -43,7 +45,9 @@ int putchar(int c)
 
 int putchar_unlocked(int c)
 {
-#ifdef CONFIG_FILE_STREAM
+#ifdef CONFIG_SYSLOG_STDOUT
+  return printf("%c", c);
+#elif defined(CONFIG_FILE_STREAM)
   return fputc_unlocked(c, stdout);
 #else
   unsigned char tmp = c;

libs/libc/stdio/lib_puts.c

@@ -44,7 +44,9 @@
 
 int puts(FAR const IPTR char *s)
 {
-#ifdef CONFIG_FILE_STREAM
+#ifdef CONFIG_SYSLOG_STDOUT
+  return printf("%s\n", s);
+#elif defined(CONFIG_FILE_STREAM)
   FILE *stream = stdout;
   int nwritten;
   int nput = EOF;