basic outline, falls apart once it hits a differing line

1 files changed, 156 insertions, 0 deletions

diff --git a/comm.c b/comm.c
new file mode 100644
index 0000000..4a05c83
--- /dev/null
+++ b/comm.c
@@ -0,0 +1,156 @@
+/*
+ * UNG's Not GNU
+ *
+ * Copyright (c) 2020, Jakob Kaivo <jkk@ung.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#define _XOPEN_SOURCE 700
+#include <errno.h>
+#include <locale.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static FILE *comm_open(const char *path)
+{
+	if (strcmp(path, "-") == 0) {
+		return stdin;
+	}
+
+	FILE *f = fopen(path, "r");
+	if (f == NULL) {
+		fprintf(stderr, "comm: %s: %s\n", path, strerror(errno));
+		exit(1);
+	}
+	return f;
+}
+
+static FILE *comm_line(FILE *f, char *buf, size_t n)
+{
+	if (f == NULL) {
+		buf[0] = '\0';
+		return NULL;
+	}
+
+	if (fgets(buf, n, f) == NULL) {
+		buf[0] = '\0';
+		fclose(f);
+		f = NULL;
+	} else {
+		char *nl = strchr(buf, '\n');
+		if (nl) {
+			*nl = '\0';
+		}
+	}
+
+	return f;
+}
+
+static int comm(FILE *f1, FILE *f2, char *lead[])
+{
+	int comp = 0;
+	char s1[LINE_MAX];
+	char s2[LINE_MAX];
+
+	while (f1 && f2) {
+		f1 = comm_line(f1, s1, sizeof(s1));
+		f2 = comm_line(f2, s2, sizeof(s2));
+
+		comp = strcoll(s1, s2);
+		if (comp == 0) {
+			if (lead[2]) {
+				printf("%s%s\n", lead[2], s1);
+			}
+			continue;
+		}
+
+		do {
+			if (lead[0]) {
+				printf("%s%s\n", lead[0], s1);
+			}
+
+			if (lead[1]) {
+				printf("%s%s\n", lead[1], s2);
+			}
+
+			if (comp < 0) {
+				f1 = comm_line(f1, s1, sizeof(s1));
+			} else {
+				f2 = comm_line(f2, s1, sizeof(s2));
+			}
+
+			comp = strcoll(s1, s2);
+		} while (comp != 0 && f1 && f2);
+	}
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	setlocale(LC_ALL, "");
+
+	char *lead[] = { "", "\t", "\t\t" };
+
+	int c;
+	while ((c = getopt(argc, argv, "123")) != -1) {
+		switch (c) {
+		case '1':
+			lead[0] = NULL;
+			lead[1] = "";
+			if (lead[2]) {
+				lead[2]++;
+			}
+			break;
+
+		case '2':
+			lead[1] = NULL;
+			if (lead[2]) {
+				lead[2]++;
+			}
+			break;
+
+		case '3':
+			lead[2] = NULL;
+			break;
+
+		default:
+			return 1;
+		}
+	}
+
+	if (optind < argc - 2) {
+		fprintf(stderr, "comm: too many operands\n");
+		return 1;
+	}
+
+	if (optind >= argc - 1) {
+		fprintf(stderr, "comm: missing operands\n");
+		return 1;
+	}
+
+	FILE *f1 = comm_open(argv[optind]);
+	FILE *f2 = comm_open(argv[optind + 1]);
+
+	return comm(f1, f2, lead);
+}