diff --git a/cat.c b/cat.c
index a0cd961..fb569f1 100644
--- a/cat.c
+++ b/cat.c
@@ -1,5 +1,6 @@
 /* See LICENSE file for copyright and license details. */
 #include <stdio.h>
+#include <string.h>
 #include <unistd.h>
 
 #include "text.h"
@@ -29,7 +30,7 @@ main(int argc, char *argv[])
 		concat(stdin, "<stdin>", stdout, "<stdout>");
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/cksum.c b/cksum.c
index 4ad78a1..9a0d195 100644
--- a/cksum.c
+++ b/cksum.c
@@ -1,6 +1,7 @@
 /* See LICENSE file for copyright and license details. */
 #include <inttypes.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "util.h"
 
@@ -96,7 +97,7 @@ main(int argc, char *argv[])
 		cksum(stdin, NULL);
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/cmp.c b/cmp.c
index 47ea1e4..c04fce6 100644
--- a/cmp.c
+++ b/cmp.c
@@ -1,6 +1,7 @@
 /* See LICENSE file for copyright and license details. */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "util.h"
 
@@ -32,7 +33,7 @@ main(int argc, char *argv[])
 		usage();
 
 	for (n = 0; n < 2; n++) {
-		if (argv[n][0] == '-' && !argv[n][1]) {
+		if (!strcmp(argv[n], "-")) {
 			argv[n] = "<stdin>";
 			fp[n] = stdin;
 		} else {
diff --git a/cols.c b/cols.c
index e5eec71..6f43e35 100644
--- a/cols.c
+++ b/cols.c
@@ -48,7 +48,7 @@ main(int argc, char *argv[])
 		getlines(stdin, &b);
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/comm.c b/comm.c
index 4464c43..661aed2 100644
--- a/comm.c
+++ b/comm.c
@@ -50,7 +50,7 @@ main(int argc, char *argv[])
 		usage();
 
 	for (i = 0; i < 2; i++) {
-		if (argv[i][0] == '-' && !argv[i][1]) {
+		if (!strcmp(argv[i], "-")) {
 			argv[i] = "<stdin>";
 			fp[i] = stdin;
 		} else if (!(fp[i] = fopen(argv[i], "r"))) {
diff --git a/cut.c b/cut.c
index b5e176e..33eecd0 100644
--- a/cut.c
+++ b/cut.c
@@ -187,7 +187,7 @@ main(int argc, char *argv[])
 		cut(stdin, "<stdin>");
 	else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/expand.c b/expand.c
index c6057f7..985dc96 100644
--- a/expand.c
+++ b/expand.c
@@ -1,6 +1,7 @@
 /* See LICENSE file for copyright and license details. */
 #include <stdint.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "utf.h"
 #include "util.h"
@@ -110,7 +111,7 @@ main(int argc, char *argv[])
 		expand("<stdin>", stdin);
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/fold.c b/fold.c
index 0a55c61..69493c0 100644
--- a/fold.c
+++ b/fold.c
@@ -95,7 +95,7 @@ main(int argc, char *argv[])
 		fold(stdin, "<stdin>");
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/grep.c b/grep.c
index e51ce09..5836eaa 100644
--- a/grep.c
+++ b/grep.c
@@ -260,7 +260,7 @@ main(int argc, char *argv[])
 		match = grep(stdin, "<stdin>");
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/head.c b/head.c
index 3f331ce..bb6b180 100644
--- a/head.c
+++ b/head.c
@@ -2,6 +2,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "util.h"
 
@@ -50,7 +51,7 @@ main(int argc, char *argv[])
 	} else {
 		many = argc > 1;
 		for (newline = 0; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/join.c b/join.c
index 0d8f152..572bed0 100644
--- a/join.c
+++ b/join.c
@@ -528,7 +528,7 @@ main(int argc, char *argv[])
 		usage();
 
 	for (n = 0; n < 2; n++) {
-		if (argv[n][0] == '-' && !argv[n][1]) {
+		if (!strcmp(argv[n], "-")) {
 			argv[n] = "<stdin>";
 			fp[n] = stdin;
 		} else if (!(fp[n] = fopen(argv[n], "r"))) {
diff --git a/nl.c b/nl.c
index 8c7b41f..3685221 100644
--- a/nl.c
+++ b/nl.c
@@ -190,7 +190,7 @@ main(int argc, char *argv[])
 	if (!argc) {
 		nl("<stdin>", stdin);
 	} else {
-		if (argv[0][0] == '-' && !argv[0][1]) {
+		if (!strcmp(argv[0], "-")) {
 			argv[0] = "<stdin>";
 			fp = stdin;
 		} else if (!(fp = fopen(argv[0], "r"))) {
diff --git a/paste.c b/paste.c
index 6f3fac2..417d93c 100644
--- a/paste.c
+++ b/paste.c
@@ -116,7 +116,7 @@ main(int argc, char *argv[])
 	dsc = ereallocarray(NULL, argc, sizeof(*dsc));
 
 	for (i = 0; i < argc; i++) {
-		if (argv[i][0] == '-' && !argv[i][1]) {
+		if (!strcmp(argv[i], "-")) {
 			argv[i] = "<stdin>";
 			dsc[i].fp = stdin;
 		} else if (!(dsc[i].fp = fopen(argv[i], "r"))) {
diff --git a/sed.c b/sed.c
index 65b3708..586cecb 100644
--- a/sed.c
+++ b/sed.c
@@ -1114,7 +1114,7 @@ next_file(void)
 			if (first) /* given no files, default to stdin */
 				file = stdin;
 			/* else we've used all our files, leave file = NULL */
-		} else if ((*files)[0] == '-' && !(*files)[1]) {
+		} else if (!strcmp(*files, "-")) {
 			file = stdin;
 			files++;
 		} else if (!(file = fopen(*files++, "r"))) {
diff --git a/sort.c b/sort.c
index 2aa4aee..f98a428 100644
--- a/sort.c
+++ b/sort.c
@@ -301,7 +301,7 @@ main(int argc, char *argv[])
 			getlines(stdin, &linebuf);
 		}
 	} else for (; *argv; argc--, argv++) {
-		if ((*argv)[0] == '-' && !(*argv)[1]) {
+		if (!strcmp(*argv, "-")) {
 			*argv = "<stdin>";
 			fp = stdin;
 		} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/strings.c b/strings.c
index 51b7eb6..0a14c20 100644
--- a/strings.c
+++ b/strings.c
@@ -2,6 +2,7 @@
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "utf.h"
 #include "util.h"
@@ -79,7 +80,7 @@ main(int argc, char *argv[])
 		strings(stdin, "<stdin>", len);
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/tail.c b/tail.c
index 3489da7..a53dcd1 100644
--- a/tail.c
+++ b/tail.c
@@ -115,7 +115,7 @@ main(int argc, char *argv[])
 		if ((many = argc > 1) && fflag)
 			usage();
 		for (newline = 0; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/unexpand.c b/unexpand.c
index feb6592..c107dbf 100644
--- a/unexpand.c
+++ b/unexpand.c
@@ -1,6 +1,7 @@
 /* See LICENSE file for copyright and license details. */
 #include <stdint.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "utf.h"
 #include "util.h"
@@ -153,7 +154,7 @@ main(int argc, char *argv[])
 		unexpand("<stdin>", stdin);
 	} else {
 		for (; *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {
diff --git a/uudecode.c b/uudecode.c
index 4641fb8..7140db7 100644
--- a/uudecode.c
+++ b/uudecode.c
@@ -246,7 +246,7 @@ main(int argc, char *argv[])
 	if (argc > 1)
 		usage();
 
-	if (!argc || (argv[0][0] == '-' && !argv[0][1])) {
+	if (!argc || !strcmp(argv[0], "-")) {
 		fp = stdin;
 		ifname = "<stdin>";
 	} else {
diff --git a/uuencode.c b/uuencode.c
index 17b59ea..fdde3d2 100644
--- a/uuencode.c
+++ b/uuencode.c
@@ -2,6 +2,7 @@
 #include <sys/stat.h>
 
 #include <stdio.h>
+#include <string.h>
 
 #include "util.h"
 
@@ -114,7 +115,7 @@ main(int argc, char *argv[])
 	if (!argc || argc > 2)
 		usage();
 
-	if (argc == 1 || (argv[0][0] == '-' && !argv[0][1])) {
+	if (argc == 1 || !strcmp(argv[0], "-")) {
 		if (mflag)
 			uuencodeb64(stdin, argv[0], "<stdin>");
 		else
diff --git a/wc.c b/wc.c
index b1bd0df..8870761 100644
--- a/wc.c
+++ b/wc.c
@@ -1,4 +1,6 @@
 /* See LICENSE file for copyright and license details. */
+#include <string.h>
+
 #include "utf.h"
 #include "util.h"
 
@@ -84,7 +86,7 @@ main(int argc, char *argv[])
 		wc(stdin, NULL);
 	} else {
 		for (many = (argc > 1); *argv; argc--, argv++) {
-			if ((*argv)[0] == '-' && !(*argv)[1]) {
+			if (!strcmp(*argv, "-")) {
 				*argv = "<stdin>";
 				fp = stdin;
 			} else if (!(fp = fopen(*argv, "r"))) {