dmesg: add --ctime to print human readable timestamps

Based on patch from "corentin.labbe" <corentin.labbe@geomatys.fr>.

Signed-off-by: Karel Zak <kzak@redhat.com>

2 files changed, 48 insertions, 7 deletions

diff --git a/sys-utils/dmesg.1 b/sys-utils/dmesg.1
index a9cb4beda..5a6910aaa 100644
--- a/sys-utils/dmesg.1
+++ b/sys-utils/dmesg.1
@@ -94,6 +94,10 @@ to query the kernel ring buffer.  This is 16392 by default.
 at first, 8192 since 1.3.54, 16384 since 2.1.113.)
 If you have set the kernel buffer to be larger than the default
 then this option can be used to view the entire buffer.
+.IP "\fB\-T, \-\-ctime\fP"
+Print human readable timestamps. The timestamp could be inaccurate!
+
+.B The time source used for the logs is not updated after system SUSPEND/RESUME.
 .IP "\fB\-t, \-\-notime\fP"
 Don't print kernel's timestampts.
 .IP "\fB\-u, \-\-userspace\fP"
diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index 0c7ab6733..b71097dc1 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -13,6 +13,7 @@
 #include <sys/klog.h>
 #include <sys/syslog.h>
 #include <sys/time.h>
+#include <sys/sysinfo.h>
 #include <ctype.h>
 #include <time.h>
 
@@ -101,6 +102,7 @@ struct dmesg_control {
 	char facilities[ARRAY_SIZE(facility_names) / NBBY + 1];
 
 	struct timeval	lasttime;	/* last printed timestamp */
+	time_t		boot_time;	/* system boot time */
 
 	int	raw:1;			/* raw mode */
 	int	fltr_lev:1;		/* filter out by levels[] */
@@ -108,6 +110,7 @@ struct dmesg_control {
 	int	decode:1;		/* use "facility: level: " prefix */
 	int	notime:1;		/* don't print timestamp */
 	int	delta:1;		/* show time deltas */
+	int	ctime:1;		/* show human readable time */
 };
 
 struct dmesg_record {
@@ -144,6 +147,8 @@ static void __attribute__((__noreturn__)) usage(FILE *out)
 		" -n, --console-level=LEVEL set level of messages printed to console\n"
 		" -r, --raw                 print the raw message buffer\n"
 		" -s, --buffer-size=SIZE    buffer size to query the kernel ring buffer\n"
+		" -T, --ctime               show human readable timestamp (could be \n"
+		"                           inaccurate if you have used SUSPEND/RESUME)\n"
 		" -t, --notime              don't print messages timestamp\n"
 		" -u, --userspace           display userspace messages\n"
 		" -V, --version             output version information and exit\n"
@@ -352,6 +357,20 @@ static int get_buffer_size()
 	return n > 0 ? n : 0;
 }
 
+static time_t get_boot_time(void)
+{
+	struct sysinfo info;
+	struct timeval tv;
+
+	if (sysinfo(&info) != 0)
+		warn(_("sysinfo failed"));
+	else if (gettimeofday(&tv, NULL) != 0)
+		warn(_("gettimeofday failed"));
+	else
+		return tv.tv_sec -= info.uptime;
+	return 0;
+}
+
 /*
  * Reads messages from kernel ring buffer
  */
@@ -499,7 +518,7 @@ static int get_next_record(struct dmesg_control *ctl, struct dmesg_record *rec)
 					if (*(begin - 1) == ']')
 						break;
 				}
-			} else if (ctl->delta) {
+			} else if (ctl->delta || ctl->ctime) {
 				begin = parse_timestamp(begin + 1, &rec->tv);
 			}
 		}
@@ -540,6 +559,7 @@ static void print_buffer(const char *buf, size_t size,
 			 struct dmesg_control *ctl)
 {
 	struct dmesg_record rec = { .next = buf, .next_size = size };
+	char tbuf[256];
 
 	if (ctl->raw) {
 		/* print whole buffer */
@@ -550,7 +570,6 @@ static void print_buffer(const char *buf, size_t size,
 	}
 
 	while (get_next_record(ctl, &rec) == 0) {
-
 		if (!rec.mesg_size)
 			continue;
 
@@ -561,16 +580,28 @@ static void print_buffer(const char *buf, size_t size,
 			printf("%-6s:%-6s: ", facility_names[rec.facility].name,
 					      level_names[rec.level].name);
 
+		*tbuf = '\0';
+		if (ctl->ctime) {
+			time_t t = ctl->boot_time + rec.tv.tv_sec;
+			if (strftime(tbuf, sizeof(tbuf), "%a %b %e %H:%M:%S %Y",
+				     localtime(&t)) == 0)
+				*tbuf = '\0';
+		}
 		if (ctl->delta) {
 			double delta = 0;
 
-			if (ctl->lasttime.tv_sec && ctl->lasttime.tv_usec)
+			if (timerisset(&ctl->lasttime))
 				delta = time_diff(&rec.tv, &ctl->lasttime);
 			ctl->lasttime = rec.tv;
 
-			printf("[%5d.%06d <%12.06f>] ",
-					(int) rec.tv.tv_sec,
-					(int) rec.tv.tv_usec, delta);
+			if (ctl->ctime && *tbuf)
+				printf("[%s ", tbuf);
+			else
+				printf("[%5d.%06d ", (int) rec.tv.tv_sec,
+						     (int) rec.tv.tv_usec);
+			printf("<%12.06f>] ", delta);
+		} else if (ctl->ctime && *tbuf) {
+			printf("[%s] ", tbuf);
 		}
 
 		safe_fwrite(rec.mesg, rec.mesg_size, stdout);
@@ -604,6 +635,7 @@ int main(int argc, char *argv[])
 		{ "raw",           no_argument,       NULL, 'r' },
 		{ "read-clear",    no_argument,	      NULL, 'c' },
 		{ "show-delta",    no_argument,	      NULL, 'd' },
+		{ "ctime",         no_argument,       NULL, 'T' },
 		{ "notime",        no_argument,       NULL, 't' },
 		{ "userspace",     no_argument,       NULL, 'u' },
 		{ "version",       no_argument,	      NULL, 'V' },
@@ -614,7 +646,7 @@ int main(int argc, char *argv[])
 	bindtextdomain(PACKAGE, LOCALEDIR);
 	textdomain(PACKAGE);
 
-	while ((c = getopt_long(argc, argv, "CcDdEf:hkl:n:rs:tuVx",
+	while ((c = getopt_long(argc, argv, "CcDdEf:hkl:n:rs:TtuVx",
 				longopts, NULL)) != -1) {
 
 		if (cmd != -1 && strchr("CcnDE", c))
@@ -666,6 +698,11 @@ int main(int argc, char *argv[])
 			if (bufsize < 4096)
 				bufsize = 4096;
 			break;
+		case 'T':
+			ctl.boot_time = get_boot_time();
+			if (ctl.boot_time)
+				ctl.ctime = 1;
+			break;
 		case 't':
 			ctl.notime = 1;
 			break;