diff --git a/sbin/md5/md5.c b/sbin/md5/md5.c
--- a/sbin/md5/md5.c
+++ b/sbin/md5/md5.c
@@ -152,12 +152,93 @@
 		(DIGEST_End*)&SKEIN1024_End, &SKEIN1024_Data, &SKEIN1024_Fd }
 };
 
+static unsigned	digest;
+static unsigned	malformed;
+static bool	gnu_emu = false;
+
 static void
 MD5_Update(MD5_CTX *c, const unsigned char *data, size_t len)
 {
 	MD5Update(c, data, len);
 }
 
+struct chksumrec {
+	char	*filename;
+	char	*chksum;
+	struct	chksumrec	*next;
+};
+
+static struct chksumrec *head = NULL;
+static struct chksumrec **next = &head;
+
+#define PADDING	7	/* extra padding for "SHA512t256 (...) = ...\n" style */
+#define CHKFILELINELEN	(HEX_DIGEST_LENGTH + MAXPATHLEN + PADDING)
+
+static int gnu_check(const char *checksumsfile)
+{
+	FILE	*inp;
+	char	linebuf[CHKFILELINELEN];
+	int	linelen;
+	int	lineno;
+	char	*filename;
+	char	*hashstr;
+	struct chksumrec	*rec;
+	const char	*digestname;
+	int	digestnamelen;
+	int	hashstrlen;
+
+	if ((inp = fopen(checksumsfile, "r")) == NULL)
+		err(1, "%s", checksumsfile);
+	digestname = Algorithm[digest].name;
+	digestnamelen = strlen(digestname);
+	hashstrlen = strlen(*(Algorithm[digest].TestOutput[0]));
+	lineno = 1;
+	while (fgets(linebuf, sizeof(linebuf), inp) != NULL) {
+		linelen = strlen(linebuf) - 1;
+		if (linelen <= 0)
+			break;
+		if (linebuf[linelen] != '\n')
+			errx(1, "malformed input line %d (len=%d)", lineno, linelen);
+		linebuf[linelen] = '\0';
+		filename = linebuf + digestnamelen + 2;
+		hashstr = linebuf + linelen - hashstrlen;
+		/*
+		 * supported formats:
+		 * BSD: <DigestName> (<Filename>): <Digest>
+		 * GNU: <Digest> [ *]<Filename>
+		 */
+		if (linelen >= digestnamelen + hashstrlen + 6 &&
+		    strncmp(linebuf, digestname, digestnamelen) == 0 &&
+		    strncmp(filename - 2, " (", 2) == 0 &&
+		    strncmp(hashstr - 4, ") = ", 4) == 0) {
+			*(hashstr - 4) = '\0';
+		} else if (linelen >= hashstrlen + 3 &&
+		    linebuf[hashstrlen] == ' ' &&
+		    (linebuf[hashstrlen] == ' ' ||
+			linebuf[hashstrlen] == '*')) {
+			linebuf[hashstrlen] = '\0';
+			hashstr = linebuf;
+			filename = linebuf + hashstrlen + 2;
+		} else {
+			malformed++;
+			continue;
+		}
+		rec = malloc(sizeof (*rec));
+		if (rec == NULL)
+			errx(1, "malloc failed");
+		rec->chksum = strdup(hashstr);
+		rec->filename = strdup(filename);
+		if (rec->chksum == NULL || rec->filename == NULL)
+			errx(1, "malloc failed");
+		rec->next = NULL;
+		*next = rec;
+		next = &rec->next;
+		lineno++;
+	}
+	fclose(inp);
+	return (lineno - 1);
+}
+
 /* Main driver.
 
 Arguments (may be any combination):
@@ -177,9 +258,9 @@
 	char   *p, *string;
 	char	buf[HEX_DIGEST_LENGTH];
 	size_t	len;
- 	unsigned	digest;
 	char	*progname;
-	bool	gnu_emu = false;
+	struct chksumrec	*rec;
+	int	numrecs;
 
  	if ((progname = strrchr(argv[0], '/')) == NULL)
  		progname = argv[0];
@@ -199,13 +280,13 @@
 	 */
 	len = strlen(progname);
 	if (len > 3 && strcmp(progname + len - 3, "sum") == 0) {
-		progname[len - 3] = '\0';
+		len -= 3;
 		rflag = 1;
 		gnu_emu = true;
 	}
 
  	for (digest = 0; digest < sizeof(Algorithm)/sizeof(*Algorithm); digest++)
- 		if (strcasecmp(Algorithm[digest].progname, progname) == 0)
+ 		if (strncasecmp(Algorithm[digest].progname, progname, len) == 0)
  			break;
 
  	if (digest == sizeof(Algorithm)/sizeof(*Algorithm))
@@ -221,8 +302,9 @@
 			break;
 		case 'c':
 			if (gnu_emu)
-				errx(1, "-c check option not supported");
-			checkAgainst = optarg;
+				numrecs = gnu_check(optarg);
+			else
+				checkAgainst = optarg;
 			break;
 		case 'p':
 			pflag = 1;
@@ -258,6 +340,16 @@
 		err(1, "unable to limit rights for stdio");
 #endif
 
+	if (gnu_emu) {
+		argc = 0;
+		argv = (char**)calloc(sizeof(char *), numrecs + 1);
+		for (rec = head; rec != NULL; rec = rec->next) {
+			argv[argc] = rec->filename;
+			argc++;
+		}
+		rec = head;
+	}
+
 	if (*argv) {
 		do {
 			if ((fd = open(*argv, O_RDONLY)) < 0) {
@@ -279,6 +371,10 @@
 					err(1, "capsicum");
 #endif
 			}
+			if (gnu_emu) {
+				checkAgainst = rec->chksum;
+				rec = rec->next;
+			}
 			p = Algorithm[digest].Fd(fd, buf);
 			(void)close(fd);
 			MDOutput(&Algorithm[digest], p, argv);
@@ -295,7 +391,12 @@
 		p = Algorithm[digest].Data(string, len, buf);
 		MDOutput(&Algorithm[digest], p, &string);
 	}
-
+	if (gnu_emu) {
+		if (malformed > 0)
+			warnx("WARNING: %d lines are improperly formatted", malformed);
+		if (checksFailed > 0)
+			warnx("WARNING: %d computed checksum did NOT match", checksFailed);
+	}
 	if (failed != 0)
 		return (1);
 	if (checksFailed != 0)
@@ -310,6 +411,8 @@
 static void
 MDOutput(const Algorithm_t *alg, char *p, char *argv[])
 {
+	bool checkfailed = false;
+
 	if (p == NULL) {
 		warn("%s", *argv);
 		failed++;
@@ -318,21 +421,26 @@
 		 * If argv is NULL we are reading from stdin, where the output
 		 * format has always been just the hash.
 		 */
-		if (qflag || argv == NULL)
+		if (qflag || argv == NULL) {
 			printf("%s", p);
-		else if (rflag)
-			printf("%s %s", p, *argv);
-		else
-			printf("%s (%s) = %s",
-			    alg->name, *argv, p);
-		if (checkAgainst && strcasecmp(checkAgainst, p) != 0)
-		{
-			checksFailed++;
-			if (!qflag)
-				printf(" [ Failed ]");
+		} else if (gnu_emu) {
+			checkfailed = strcasecmp(checkAgainst, p) != 0;
+			printf("%s: %s", *argv, checkfailed ? "FAILED" : "OK");
+		} else {
+			if (rflag)
+				printf("%s %s", p, *argv);
+			else
+				printf("%s (%s) = %s", alg->name, *argv, p);
+			if (checkAgainst) {
+				checkfailed = strcasecmp(checkAgainst, p) != 0;
+				if (!qflag && checkfailed)
+					printf(" [ Failed ]");
+			}
 		}
 		printf("\n");
 	}
+	if (checkfailed)
+		checksFailed++;
 }
 
 /*
@@ -559,6 +667,9 @@
 usage(const Algorithm_t *alg)
 {
 
-	fprintf(stderr, "usage: %s [-pqrtx] [-c string] [-s string] [files ...]\n", alg->progname);
+	if (gnu_emu)
+		fprintf(stderr, "usage: %ssum [-pqrtx] [-c file] [-s string] [files ...]\n", alg->progname);
+	else
+		fprintf(stderr, "usage: %s [-pqrtx] [-c string] [-s string] [files ...]\n", alg->progname);
 	exit(1);
 }