From 90e99a1c18705f654c61e3e96939b2e053baab1e Mon Sep 17 00:00:00 2001
From: Timo Kokkonen <timo.t.kokkonen@iki.fi>
Date: Mon, 7 Oct 2013 20:58:23 +0300
Subject: [PATCH] Add timestamp to the output data.

Proper timestamps are required in order to print time on the X axis of
the output graphs.

Signed-off-by: Timo Kokkonen <timo.t.kokkonen@iki.fi>
---
 main.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/main.c b/main.c
index 6cfdd87..388f63e 100644
--- a/main.c
+++ b/main.c
@@ -2,6 +2,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <string.h>
+#include <time.h>
 #include <sys/epoll.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -67,6 +68,7 @@ static int read_log_line(int infd, char *buf, size_t bufsize, int *offset)
 static int read_data(int infd, int outfd)
 {
 	struct epoll_event ev;
+	time_t start_time = 0, cur_time;
 	int epoll_fd;
 	int ret;
 	char buf[256];
@@ -86,6 +88,9 @@ static int read_data(int infd, int outfd)
 	}
 
 	while (1) {
+		char str[320];
+		int len;
+
 		ret = epoll_wait(epoll_fd, &ev, 1, -1);
 		if (ret == 0)
 			continue;
@@ -95,6 +100,9 @@ static int read_data(int infd, int outfd)
 			return -1;
 		}
 
+		if (!start_time)
+			start_time = time(NULL);
+
 		ret = read_log_line(infd, buf, sizeof(buf), &offset);
 		if (ret < 0)
 			return ret;
@@ -102,21 +110,21 @@ static int read_data(int infd, int outfd)
 		if (ret == 0)
 			continue;
 
-		if (outfd) {
-			char newline = '\n';
-			ret = write(outfd, buf, strlen(buf));
-			if (read < 0) {
-				pr_err("write: %m\n");
-				break;
-			}
-			ret = write(outfd, &newline, 1);
-			if (read < 0) {
-				pr_err("write: %m\n");
-				break;
-			}
-		}
+		cur_time = time(NULL);
 
 		pr_info("%s\n", buf);
+
+		if (!outfd)
+			continue;
+
+		len = snprintf(str, sizeof(str),
+			"%ld;%s\n", cur_time - start_time, buf);
+
+		ret = write(outfd, str, len);
+		if (read < 0) {
+			pr_err("write: %m\n");
+			break;
+		}
 	}
 
 	return 0;
-- 
2.45.0