Redirect stdout to stderr

- daemon: New feature for LoggingMode at /etc/dlt.conf to be able to
set value at 3 in order to redirect all stdout messages to stderr.

- libdlt: New feature for DLT_LOG_MODE environment variable to be able
to set value at 3 in order to redirect all stdout messages to stderr.

- unit test:  Add test cases for DLT_LOG_TO_STDERR

Signed-off-by: LUONG HONG DUY KHANH(RBVH/ENG42) <KHANH.LUONGHONGDUY@vn.bosch.com>

5 files changed, 69 insertions, 21 deletions

diff --git a/doc/dlt.conf.5.md b/doc/dlt.conf.5.md
index 6dd9ee5..4b30150 100644
--- a/doc/dlt.conf.5.md
+++ b/doc/dlt.conf.5.md
@@ -63,7 +63,7 @@ This is the directory path, where the DLT daemon stores its runtime configuratio
 
 ## LoggingMode
 
-The logging console for internal logging of dlt-daemon. 0 = log to stdout, 1 = log to syslog, 2 = log to file (see LoggingFilename)
+The logging console for internal logging of dlt-daemon. 0 = log to stdout, 1 = log to syslog, 2 = log to file (see LoggingFilename), 3 = log to stderr
 
     Default: 0
 
diff --git a/include/dlt/dlt_common.h b/include/dlt/dlt_common.h
index e5e4a22..026cf75 100644
--- a/include/dlt/dlt_common.h
+++ b/include/dlt/dlt_common.h
@@ -185,7 +185,8 @@ enum {
     DLT_LOG_TO_CONSOLE = 0,
     DLT_LOG_TO_SYSLOG = 1,
     DLT_LOG_TO_FILE = 2,
-    DLT_LOG_DROPPED = 3
+    DLT_LOG_TO_STDERR = 3,
+    DLT_LOG_DROPPED = 4
 };
 
 /**
@@ -1127,10 +1128,16 @@ void dlt_log_set_filename(const char *filename);
 void dlt_log_set_level(int level);
 /**
  * Initialize (external) logging facility
- * @param mode positive, 0 = log to stdout, 1 = log to syslog, 2 = log to file
+ * @param mode positive, 0 = log to stdout, 1 = log to syslog, 2 = log to file, 3 = log to stderr
  */
 void dlt_log_init(int mode);
 /**
+ * Print with variable arguments to specified file descriptor by DLT_LOG_MODE environment variable (like fprintf)
+ * @param format format string for message
+ * @return negative value if there was an error or the total number of characters written is returned on success
+ */
+int dlt_user_printf(const char *format, ...);
+/**
  * Log ASCII string with null-termination to (external) logging facility
  * @param prio priority (see syslog() call)
  * @param s Pointer to ASCII string with null-termination
diff --git a/src/daemon/dlt.conf b/src/daemon/dlt.conf
index 091f0d6..60d3315 100644
--- a/src/daemon/dlt.conf
+++ b/src/daemon/dlt.conf
@@ -35,7 +35,10 @@ SharedMemorySize = 100000
 # PersistanceStoragePath = /tmp
 
 # The logging console for internal logging of dlt-daemon (Default: 0)
-# 0 = log to stdout, 1 = log to syslog, 2 = log to file (see LoggingFilename)
+# 0 = log to stdout
+# 1 = log to syslog
+# 2 = log to file (see LoggingFilename)
+# 3 = log to stderr
 LoggingMode = 0
 
 # The internal log level, up to which logs are written (Default: 6)
diff --git a/src/shared/dlt_common.c b/src/shared/dlt_common.c
index 670b01b..c462ed0 100644
--- a/src/shared/dlt_common.c
+++ b/src/shared/dlt_common.c
@@ -110,9 +110,9 @@ void dlt_print_hex(uint8_t *ptr, int size)
 
     for (num = 0; num < size; num++) {
         if (num > 0)
-            printf(" ");
+            dlt_user_printf(" ");
 
-        printf("%.2x", ((uint8_t *)ptr)[num]);
+        dlt_user_printf("%.2x", ((uint8_t *)ptr)[num]);
     }
 }
 
@@ -1754,7 +1754,7 @@ void dlt_log_init(int mode)
         logging_handle = fopen(logging_filename, "a");
 
         if (logging_handle == NULL) {
-            printf("Internal log file %s cannot be opened!\n", logging_filename);
+            dlt_user_printf("Internal log file %s cannot be opened!\n", logging_filename);
             return;
         }
     }
@@ -1766,6 +1766,29 @@ void dlt_log_free(void)
         fclose(logging_handle);
 }
 
+int dlt_user_printf(const char *format, ...)
+{
+    va_list args;
+    va_start(args, format);
+
+    int ret = 0;
+    switch (logging_mode) {
+        case DLT_LOG_TO_CONSOLE:
+        case DLT_LOG_TO_SYSLOG:
+        case DLT_LOG_TO_FILE:
+        case DLT_LOG_DROPPED:
+        default:
+            ret = vfprintf(stdout, format, args);
+            break;
+        case DLT_LOG_TO_STDERR:
+            ret = vfprintf(stderr, format, args);
+            break;
+    }
+    va_end(args);
+
+    return ret;
+}
+
 DltReturnValue dlt_log(int prio, char *s)
 {
     static const char asSeverity[LOG_DEBUG +
@@ -1789,7 +1812,7 @@ DltReturnValue dlt_log(int prio, char *s)
     switch (logging_mode) {
     case DLT_LOG_TO_CONSOLE:
         /* log to stdout */
-        printf(sFormatString,
+        fprintf(stdout, sFormatString,
                (unsigned int)sTimeSpec.tv_sec,
                (unsigned int)(sTimeSpec.tv_nsec / 1000),
                getpid(),
@@ -1797,6 +1820,15 @@ DltReturnValue dlt_log(int prio, char *s)
                s);
         fflush(stdout);
         break;
+    case DLT_LOG_TO_STDERR:
+        /* log to stderr */
+        fprintf(stderr, sFormatString,
+               (unsigned int)sTimeSpec.tv_sec,
+               (unsigned int)(sTimeSpec.tv_nsec / 1000),
+               getpid(),
+               asSeverity[prio],
+               s);
+        break;
     case DLT_LOG_TO_SYSLOG:
         /* log to syslog */
 #if !defined (__WIN32__) && !defined(_MSC_VER)
@@ -3106,7 +3138,7 @@ DltReturnValue dlt_message_print_header(DltMessage *message, char *text, uint32_
         return DLT_RETURN_WRONG_PARAMETER;
 
     dlt_message_header(message, text, size, verbose);
-    printf("%s\n", text);
+    dlt_user_printf("%s\n", text);
 
     return DLT_RETURN_OK;
 }
@@ -3117,9 +3149,9 @@ DltReturnValue dlt_message_print_hex(DltMessage *message, char *text, uint32_t s
         return DLT_RETURN_WRONG_PARAMETER;
 
     dlt_message_header(message, text, size, verbose);
-    printf("%s ", text);
+    dlt_user_printf("%s ", text);
     dlt_message_payload(message, text, size, DLT_OUTPUT_HEX, verbose);
-    printf("[%s]\n", text);
+    dlt_user_printf("[%s]\n", text);
 
     return DLT_RETURN_OK;
 }
@@ -3130,9 +3162,9 @@ DltReturnValue dlt_message_print_ascii(DltMessage *message, char *text, uint32_t
         return DLT_RETURN_WRONG_PARAMETER;
 
     dlt_message_header(message, text, size, verbose);
-    printf("%s ", text);
+    dlt_user_printf("%s ", text);
     dlt_message_payload(message, text, size, DLT_OUTPUT_ASCII, verbose);
-    printf("[%s]\n", text);
+    dlt_user_printf("[%s]\n", text);
 
     return DLT_RETURN_OK;
 }
@@ -3143,9 +3175,9 @@ DltReturnValue dlt_message_print_mixed_plain(DltMessage *message, char *text, ui
         return DLT_RETURN_WRONG_PARAMETER;
 
     dlt_message_header(message, text, size, verbose);
-    printf("%s \n", text);
+    dlt_user_printf("%s \n", text);
     dlt_message_payload(message, text, size, DLT_OUTPUT_MIXED_FOR_PLAIN, verbose);
-    printf("[%s]\n", text);
+    dlt_user_printf("[%s]\n", text);
 
     return DLT_RETURN_OK;
 }
@@ -3156,9 +3188,9 @@ DltReturnValue dlt_message_print_mixed_html(DltMessage *message, char *text, uin
         return DLT_RETURN_WRONG_PARAMETER;
 
     dlt_message_header(message, text, size, verbose);
-    printf("%s \n", text);
+    dlt_user_printf("%s \n", text);
     dlt_message_payload(message, text, size, DLT_OUTPUT_MIXED_FOR_HTML, verbose);
-    printf("[%s]\n", text);
+    dlt_user_printf("[%s]\n", text);
 
     return DLT_RETURN_OK;
 }
diff --git a/tests/gtest_dlt_common.cpp b/tests/gtest_dlt_common.cpp
index 364afbe..04fdbc6 100644
--- a/tests/gtest_dlt_common.cpp
+++ b/tests/gtest_dlt_common.cpp
@@ -3566,13 +3566,15 @@ TEST(t_dlt_log_set_level, normal)
     /* DLT_LOG_TO_CONSOLE=0, */
     /* DLT_LOG_TO_SYSLOG=1, */
     /* DLT_LOG_TO_FILE=2, */
-    /* DLT_LOG_DROPPED=3 */
+    /* DLT_LOG_TO_STDERR=3, */
+    /* DLT_LOG_DROPPED=4 */
     /*####################### */
 
-    /* Normal Use-Case, expcect 0-3 */
+    /* Normal Use-Case, expect 0-4 */
     EXPECT_NO_THROW(dlt_log_set_level(DLT_LOG_TO_CONSOLE));
     EXPECT_NO_THROW(dlt_log_set_level(DLT_LOG_TO_SYSLOG));
     EXPECT_NO_THROW(dlt_log_set_level(DLT_LOG_TO_FILE));
+    EXPECT_NO_THROW(dlt_log_set_level(DLT_LOG_TO_STDERR));
     EXPECT_NO_THROW(dlt_log_set_level(DLT_LOG_DROPPED));
 }
 TEST(t_dlt_log_set_level, abnormal)
@@ -3619,7 +3621,8 @@ TEST(t_dlt_log_init, normal)
     /* DLT_LOG_TO_CONSOLE=0, */
     /* DLT_LOG_TO_SYSLOG=1, */
     /* DLT_LOG_TO_FILE=2, */
-    /* DLT_LOG_DROPPED=3 */
+    /* DLT_LOG_TO_STDERR=3, */
+    /* DLT_LOG_DROPPED=4 */
     /*####################### */
 
     /* Normal Use-Case, exptect 0-3 */
@@ -3628,6 +3631,7 @@ TEST(t_dlt_log_init, normal)
     EXPECT_NO_THROW(dlt_log_set_filename("/tmp/dlt.log"));
     EXPECT_NO_THROW(dlt_log_init(DLT_LOG_TO_FILE));
     EXPECT_NO_THROW(dlt_log_init(DLT_LOG_TO_FILE));
+    EXPECT_NO_THROW(dlt_log_init(DLT_LOG_TO_STDERR));
     EXPECT_NO_THROW(dlt_log_init(DLT_LOG_DROPPED));
 }
 TEST(t_dlt_log_init, abnormal)
@@ -3651,12 +3655,14 @@ TEST(t_dlt_log_free, normal)
     /* DLT_LOG_TO_CONSOLE=0, */
     /* DLT_LOG_TO_SYSLOG=1, */
     /* DLT_LOG_TO_FILE=2, */
-    /* DLT_LOG_DROPPED=3 */
+    /* DLT_LOG_TO_STDERR=3, */
+    /* DLT_LOG_DROPPED=4 */
     /*####################### */
 
     /* Normal Use-Case, expected 0 */
     EXPECT_NO_THROW(dlt_log_init(DLT_LOG_TO_CONSOLE));
     EXPECT_NO_THROW(dlt_log_init(DLT_LOG_TO_SYSLOG));
+    EXPECT_NO_THROW(dlt_log_init(DLT_LOG_TO_STDERR));
     EXPECT_NO_THROW(dlt_log_init(DLT_LOG_DROPPED));
 }
 TEST(t_dlt_log_free, abnormal)