diff --git a/README b/README
index 323dc84..3072baf 100644
--- a/README
+++ b/README
@@ -18,7 +18,7 @@ The following tools are implemented (* == finished):
 * cksum           yes                             none
 * cmp             yes                             none
 * cols            non-posix                       none
-  comm            yes                             none
+* comm            yes                             none
   cp              no                              -H, -i, -L
 * cron            non-posix                       none
   cut             yes                             none
diff --git a/comm.1 b/comm.1
index 8081775..6248483 100644
--- a/comm.1
+++ b/comm.1
@@ -1,33 +1,43 @@
-.TH COMM 1 sbase\-VERSION
-.SH NAME
-comm \- select or reject lines common to two files
-.SH SYNOPSIS
-.B comm
-.RB [ \-123 ]
-.IR file1
-.IR file2
-.SH DESCRIPTION
-The comm utility reads
-.IR file1
+.Dd January 18, 2015
+.Dt COMM 1 sbase\-VERSION
+.Sh NAME
+.Nm comm
+.Nd select or reject lines common to two files
+.Sh SYNOPSIS
+.Nm comm
+.Op Fl 123
+.Ar file1
+.Ar file2
+.Sh DESCRIPTION
+.Nm
+reads
+.Ar file1
 and
-.IR file2,
-which should be sorted lexically,
-and produces three text columns as output: lines only in
-.IR file1;
-lines only in
-.IR file2;
-and lines in both files.
-.SH OPTIONS
-.TP
-.BI \-1
-Suppress printing of column 1
-.TP
-.BI \-2
-Suppress printing of column 2
-.TP
-.BI \-3
-Suppress printing of column 3
-.SH SEE ALSO
-.IR cmp (1),
-.IR sort (1),
-.IR uniq (1)
+.Ar file2,
+which should both be sorted lexically, and writes three text columns
+to stdout:
+.Bl -tag -width Ds
+.It 1
+Lines only in
+.Ar file1 .
+.It 2
+Lines only in
+.Ar file2 .
+.It 3
+Common lines.
+.El
+.Sh OPTIONS
+.Bl -tag -width Ds
+.It Fl 1 | Fl 2 | Fl 3
+Suppress column 1 | 2 | 3
+.El
+.Sh SEE ALSO
+.Xr cmp 1 ,
+.Xr sort 1 ,
+.Xr uniq 1
+.Sh STANDARDS
+The
+.Nm
+utility is compliant with the
+.St -p1003.1-2008
+specification.
diff --git a/comm.c b/comm.c
index a946cba..ac2111b 100644
--- a/comm.c
+++ b/comm.c
@@ -8,12 +8,44 @@
 
 #define CLAMP(x, l, h) MIN(h, MAX(l, x))
 
-static void printline(int, char *);
-static char *nextline(char *, int, FILE *, char *);
-static void finish(int, FILE *, char *);
-
 static int show = 0x07;
 
+static void
+printline(int pos, char *line)
+{
+	int i;
+
+	if (!(show & (0x1 << pos)))
+		return;
+
+	for (i = 0; i < pos; i++) {
+		if (show & (0x1 << i))
+			putchar('\t');
+	}
+	printf("%s", line);
+}
+
+static char *
+nextline(char *buf, int n, FILE *f, char *name)
+{
+	buf = fgets(buf, n, f);
+	if (!buf && !feof(f))
+		eprintf("%s: read error:", name);
+	if (buf && !strchr(buf, '\n'))
+		eprintf("%s: line too long\n", name);
+	return buf;
+}
+
+static void
+finish(int pos, FILE *f, char *name)
+{
+	char buf[LINE_MAX + 1];
+
+	while (nextline(buf, sizeof(buf), f, name))
+		printline(pos, buf);
+	exit(1);
+}
+
 static void
 usage(void)
 {
@@ -25,7 +57,7 @@ main(int argc, char *argv[])
 {
 	int i, diff = 0;
 	FILE *fp[2];
-	char lines[2][LINE_MAX+1];
+	char lines[2][LINE_MAX + 1];
 
 	ARGBEGIN {
 	case '1':
@@ -73,39 +105,3 @@ main(int argc, char *argv[])
 
 	return 0;
 }
-
-static void
-printline(int pos, char *line)
-{
-	int i;
-
-	if (!(show & (0x1 << pos)))
-		return;
-
-	for (i = 0; i < pos; i++) {
-		if (show & (0x1 << i))
-			putchar('\t');
-	}
-	printf("%s", line);
-}
-
-static char *
-nextline(char *buf, int n, FILE *f, char *name)
-{
-	buf = fgets(buf, n, f);
-	if (!buf && !feof(f))
-		eprintf("%s: read error:", name);
-	if (buf && !strchr(buf, '\n'))
-		eprintf("%s: line too long\n", name);
-	return buf;
-}
-
-static void
-finish(int pos, FILE *f, char *name)
-{
-	char buf[LINE_MAX+1];
-
-	while (nextline(buf, sizeof(buf), f, name))
-		printline(pos, buf);
-	exit(1);
-}