From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Thu, 19 Feb 2026 17:14:23 +0000 (+0100)
Subject: dmesg: Gracefully handle EPIPE errors
X-Git-Tag: v2.43-devel~53^2~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=01745e8593420f864d0904b5a4913796e513f97d;p=thirdparty%2Futil-linux.git

dmesg: Gracefully handle EPIPE errors

Just calling exit with a success return value in case of an EPIPE error
in safe_fwrite is not precise enough. If dmesg was called with "-c",
i.e. to print and then clear the ring buffer, a successful return value
should mean that the ring buffer is cleared as well.

Instead, continue operation on EPIPE error but stop any further regular
output.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
---

diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index b6f506034..cd042f549 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -821,11 +821,8 @@ doprint:
 		} else
 			rc = fwrite(p, 1, len, out) != len;
 
-		if (rc != 0) {
-			if (errno != EPIPE)
-				err(EXIT_FAILURE, _("write failed"));
-			exit(EXIT_SUCCESS);
-		}
+		if (rc != 0 && errno != EPIPE)
+			err(EXIT_FAILURE, _("write failed"));
 	}
 }
 
@@ -1012,7 +1009,7 @@ static void raw_print(struct dmesg_control *ctl, const char *buf, size_t size)
 		/*
 		 * Print file in small chunks to save memory
 		 */
-		while (size) {
+		while (size && !ferror(stdout)) {
 			size_t sz = size > ctl->pagesize ? ctl->pagesize : size;
 			char *x = ctl->mmap_buff;
 
@@ -1380,7 +1377,7 @@ static void print_buffer(struct dmesg_control *ctl,
 		return;
 	}
 
-	while (get_next_syslog_record(ctl, &rec) == 0)
+	while (get_next_syslog_record(ctl, &rec) == 0 && !ferror(stdout))
 		print_record(ctl, &rec);
 }
 
@@ -1549,7 +1546,7 @@ static int print_kmsg(struct dmesg_control *ctl)
 	 */
 	sz = ctl->kmsg_first_read;
 
-	while (sz > 0) {
+	while (sz > 0 && !ferror(stdout)) {
 		*(ctl->kmsg_buf + sz) = '\0';	/* for debug messages */
 
 		if (parse_kmsg_record(ctl, &rec,
@@ -1571,7 +1568,7 @@ static int print_kmsg_file(struct dmesg_control *ctl, size_t sz)
 	if (ctl->method != DMESG_METHOD_KMSG || !ctl->filename)
 		return -1;
 
-	while (sz > 0) {
+	while (sz > 0 && !ferror(stdout)) {
 		len = strnlen(ctl->mmap_buff, sz);
 		if (len > sizeof(str))
 			errx(EXIT_FAILURE, _("record too large"));