diff --git a/expand.c b/expand.c
index 68336ec..7ad43b8 100644
--- a/expand.c
+++ b/expand.c
@@ -14,7 +14,7 @@ static int expand(Fdescr *f, int tabstop);
 static void
 usage(void)
 {
-	eprintf("usage: %s [-t n] [file...]\n", argv0);
+	eprintf("usage: %s [-i] [-t n] [file...]\n", argv0);
 }
 
 int
@@ -25,6 +25,8 @@ main(int argc, char *argv[])
 	int tabstop = 8;
 
 	ARGBEGIN {
+	case 'i':
+		eprintf("not implemented\n");
 	case 't':
 		tabstop = estrtol(EARGF(usage()), 0);
 		break;
diff --git a/md5sum.c b/md5sum.c
index 4fd449f..7618663 100644
--- a/md5sum.c
+++ b/md5sum.c
@@ -17,7 +17,7 @@ struct crypt_ops md5_ops = {
 static void
 usage(void)
 {
-	eprintf("usage: %s [file...]\n", argv0);
+	eprintf("usage: %s [-c] [file...]\n", argv0);
 }
 
 int
@@ -27,6 +27,8 @@ main(int argc, char *argv[])
 	uint8_t md[MD5_DIGEST_LENGTH];
 
 	ARGBEGIN {
+	case 'c':
+		eprintf("not implemented\n");
 	default:
 		usage();
 	} ARGEND;
diff --git a/readlink.c b/readlink.c
index 065c05d..f54fd51 100644
--- a/readlink.c
+++ b/readlink.c
@@ -11,7 +11,7 @@
 static void
 usage(void)
 {
-	eprintf("usage: %s [-fn] file\n", argv0);
+	eprintf("usage: %s [-efmn] file\n", argv0);
 }
 
 int
@@ -23,6 +23,9 @@ main(int argc, char *argv[])
 	ssize_t n;
 
 	ARGBEGIN {
+	case 'e':
+	case 'm':
+		eprintf("not implemented\n");
 	case 'f':
 		fflag = true;
 		break;
diff --git a/sha1sum.c b/sha1sum.c
index 11b9111..6d79f15 100644
--- a/sha1sum.c
+++ b/sha1sum.c
@@ -17,7 +17,7 @@ struct crypt_ops sha1_ops = {
 static void
 usage(void)
 {
-	eprintf("usage: %s [file...]\n", argv0);
+	eprintf("usage: %s [-c] [file...]\n", argv0);
 }
 
 int
@@ -27,6 +27,8 @@ main(int argc, char *argv[])
 	uint8_t md[SHA1_DIGEST_LENGTH];
 
 	ARGBEGIN {
+	case 'c':
+		eprintf("not implemented\n");
 	default:
 		usage();
 	} ARGEND;
diff --git a/sha256sum.c b/sha256sum.c
index ce97435..5dfc6a5 100644
--- a/sha256sum.c
+++ b/sha256sum.c
@@ -17,7 +17,7 @@ struct crypt_ops sha256_ops = {
 static void
 usage(void)
 {
-	eprintf("usage: %s [file...]\n", argv0);
+	eprintf("usage: %s [-c] [file...]\n", argv0);
 }
 
 int
@@ -27,6 +27,8 @@ main(int argc, char *argv[])
 	uint8_t md[SHA256_DIGEST_LENGTH];
 
 	ARGBEGIN {
+	case 'c':
+		eprintf("not implemented\n");
 	default:
 		usage();
 	} ARGEND;
diff --git a/sha512sum.c b/sha512sum.c
index 972f2c7..edb1cd3 100644
--- a/sha512sum.c
+++ b/sha512sum.c
@@ -17,7 +17,7 @@ struct crypt_ops sha512_ops = {
 static void
 usage(void)
 {
-	eprintf("usage: %s [file...]\n", argv0);
+	eprintf("usage: %s [-c] [file...]\n", argv0);
 }
 
 int
@@ -27,6 +27,8 @@ main(int argc, char *argv[])
 	uint8_t md[SHA512_DIGEST_LENGTH];
 
 	ARGBEGIN {
+	case 'c':
+		eprintf("not implemented\n");
 	default:
 		usage();
 	} ARGEND;
diff --git a/uniq.c b/uniq.c
index 7eb49f3..9c85668 100644
--- a/uniq.c
+++ b/uniq.c
@@ -22,7 +22,7 @@ static long prev_line_count = 0;
 static void
 usage(void)
 {
-	eprintf("usage: %s [-cdu] [input]]\n", argv0);
+	eprintf("usage: %s [-cdiu] [input]]\n", argv0);
 }
 
 int
@@ -31,6 +31,8 @@ main(int argc, char *argv[])
 	FILE *fp;
 
 	ARGBEGIN {
+	case 'i':
+		eprintf("not implemented\n");
 	case 'c':
 		countfmt = "%7ld ";
 		break;