From: Karel Zak <kzak@redhat.com>
Date: Thu, 12 Mar 2026 11:56:14 +0000 (+0100)
Subject: dmesg: fix -d -t (--show-delta --notime) output regression
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e795adc5bbbac961e70bb402c9fce2397b059bf6;p=thirdparty%2Futil-linux.git

dmesg: fix -d -t (--show-delta --notime) output regression

When -d and -t are used together, only the time delta should be
printed without the timestamp prefix. This was broken because
DMESG_TIMEFTM_NONE in the format list caused the print_record()
loop to break early before processing the delta format.

Resolve the conflict after option parsing: when NONE coexists with
a delta format (TIME_DELTA or DELTA), replace all formats with just
DELTA. When NONE is used without delta, it suppresses all timestamps
as before.

Fixes: https://github.com/util-linux/util-linux/issues/4110
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index f4ff3e2c5..5496bdbe4 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -1879,6 +1879,24 @@ int main(int argc, char *argv[])
 			ctl.suspended_time = dmesg_get_suspended_time();
 	}
 
+	/*
+	 * Resolve NONE (--notime) vs. delta combinations. When both are
+	 * specified (e.g. -d -t), delta wins and timestamp is suppressed.
+	 * When NONE is used without delta, it suppresses all timestamps.
+	 */
+	if (is_time_fmt_set(&ctl, DMESG_TIMEFTM_NONE)) {
+		if (is_time_fmt_set(&ctl, DMESG_TIMEFTM_TIME_DELTA)
+		    || is_time_fmt_set(&ctl, DMESG_TIMEFTM_DELTA)) {
+			reset_time_fmts(&ctl);
+			ctl.ntime_fmts = 0;
+			include_time_fmt(&ctl, DMESG_TIMEFTM_DELTA);
+		} else {
+			reset_time_fmts(&ctl);
+			ctl.ntime_fmts = 0;
+			include_time_fmt(&ctl, DMESG_TIMEFTM_NONE);
+		}
+	}
+
 	/* -d uses TIME_DELTA; merge with -T (CTIME) if both specified */
 	if (is_time_fmt_set(&ctl, DMESG_TIMEFTM_TIME_DELTA)
 	    && is_time_fmt_set(&ctl, DMESG_TIMEFTM_CTIME)) {