Add comm

Signed-off-by: Christoph Lohmann <20h@r-36.net>

Makefile

@@ -29,6 +29,7 @@ SRC = \
 	chvt.c     \
 	cksum.c    \
 	cmp.c      \
+	comm.c     \
 	cp.c       \
 	date.c     \
 	dirname.c  \

TODO

@@ -1,7 +1,5 @@
 cal [-1] [-3] [-y] [year]
 
-comm [-123] file1 file2
-
 cut [-bcfs] [-d delim] list [file...]
 
 df [-shia] [path]

comm.1

@@ -0,0 +1,33 @@
+.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
+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)

comm.c

@@ -0,0 +1,132 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "util.h"
+
+enum { Suppress1 = 1, Suppress2 = 2, Suppress3 = 4 };
+
+static void comm(FILE *fp1, const char *s1, FILE *fp2,
+		 const char *s2, int sflags);
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [-123] file1 file2\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int sflags = 0;
+	FILE *fp1, *fp2;
+
+	ARGBEGIN {
+	case '1':
+		sflags |= Suppress1;
+		break;
+	case '2':
+		sflags |= Suppress2;
+		break;
+	case '3':
+		sflags |= Suppress3;
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (argc < 2)
+		usage();
+
+	if (!(fp1 = fopen(argv[0], "r")))
+		eprintf("fopen %s:", argv[0]);
+	if (!(fp2 = fopen(argv[1], "r")))
+		eprintf("fopen %s:", argv[1]);
+
+	comm(fp1, argv[0], fp2, argv[1], sflags);
+
+	return 0;
+}
+
+static void
+print_col1(const char *s, int sflags)
+{
+	if (sflags & Suppress1)
+		return;
+	printf("%s", s);
+}
+
+static void
+print_col2(const char *s, int sflags)
+{
+	const char *tabs = "\t";
+	if (sflags & Suppress1)
+		tabs = "";
+	if (sflags & Suppress2)
+		return;
+	printf("%s%s", tabs, s);
+}
+
+static void
+print_col3(const char *s, int sflags)
+{
+	const char *tabs = "\t\t";
+	if (sflags & Suppress1)
+		tabs = "\t";
+	if (sflags & Suppress2)
+		tabs = "";
+	if (sflags & Suppress3)
+		return;
+	printf("%s%s", tabs, s);
+}
+
+static void
+comm(FILE *fp1, const char *s1, FILE *fp2, const char *s2, int sflags)
+{
+	char buf1[BUFSIZ], buf2[BUFSIZ];
+	bool eof1 = false, eof2 = false;
+	bool r1 = true, r2 = true;
+	int ret;
+
+	for (;;) {
+		if (r1)
+			if (!fgets(buf1, sizeof buf1, fp1))
+				eof1 = true;
+		if (r2)
+			if (!fgets(buf2, sizeof buf2, fp2))
+				eof2 = true;
+
+		/* If we reached EOF on fp1 then just dump fp2 */
+		if (eof1) {
+			do {
+				print_col2(buf2, sflags);
+			} while (fgets(buf2, sizeof buf2, fp2));
+			return;
+		}
+		/* If we reached EOF on fp2 then just dump fp1 */
+		if (eof2) {
+			do {
+				print_col1(buf1, sflags);
+			} while (fgets(buf1, sizeof buf1, fp1));
+			return;
+		}
+
+		ret = strcmp(buf1, buf2);
+		if (!ret) {
+			r1 = r2 = true;
+			print_col3(buf1, sflags);
+			continue;
+		} else if (ret < 0) {
+			r1 = true;
+			r2 = false;
+			print_col1(buf1, sflags);
+			continue;
+		} else {
+			r1 = false;
+			r2 = true;
+			print_col2(buf2, sflags);
+			continue;
+		}
+	}
+}