initial version working for offsets from start of file

1 files changed, 155 insertions, 0 deletions

diff --git a/tail.c b/tail.c
new file mode 100644
index 0000000..b6e49ba
--- /dev/null
+++ b/tail.c
@@ -0,0 +1,155 @@
+/*
+ * UNG's Not GNU
+ *
+ * Copyright (c) 2011-2019, 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 _POSIX_C_SOURCE 2
+#include <ctype.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <locale.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+enum { BYTES, LINES };
+
+static int tail(const char *path, int follow, int unit, intmax_t count)
+{
+	FILE *f = stdin;
+	if (path && strcmp(path, "-")) {
+		f = fopen(path, "r");
+	}
+
+	if (f == NULL) {
+		fprintf(stderr, "tail: %s: %s\n", path, strerror(errno));
+		return 1;
+	}
+
+	int c;
+	while (count > 0) {
+		c = fgetc(f);
+		if (unit == BYTES || c == '\n') {
+			count--;
+		}
+	}
+
+	while (count == 0 && (c = fgetc(f)) != EOF) {
+		putchar(c);
+	}
+
+	while (count < 0) {
+		/* work from the end */
+	}
+
+	while (follow) {
+		char buf[BUFSIZ];
+		ssize_t nread = read(fileno(f), buf, sizeof(buf));
+		write(STDOUT_FILENO, buf, nread);
+	}
+
+	if (f != stdin) {
+		fclose(f);
+	}
+
+	return 0;
+}
+
+void fixobsolete(int argc, char *argv[])
+{
+	for (int i = 1; i < argc; i++) {
+		if (!strcmp(argv[i], "--")) {
+			return;
+		}
+
+		if (!strcmp(argv[i], "-n")) {
+			i++;
+			continue;
+		}
+
+		if (!strcmp(argv[i], "-c")) {
+			i++;
+			continue;
+		}
+
+		if (argv[i][0] == '+') {
+			if (!isdigit(argv[i][1])) {
+				argv[i][0] = '-';
+				continue;
+			}
+
+			fprintf(stderr, "tail: +# is obsolete; use -n or -l\n");
+			/* TODO: convert */
+		}
+
+		if (argv[i][0] == '-' && isdigit(argv[i][1])) {
+			fprintf(stderr, "tail: -# is obsolete; use -n or -l\n");
+			char *opt = malloc(strlen(argv[i]) + 3);
+			if (opt == NULL) {
+				perror("tail");
+				exit(1);
+			}
+			/* TODO */
+			/* no suffix or 'l' => -l */
+			/* 'c' => -c */
+			/* 'b' => -c 512 * n */
+		}
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	setlocale(LC_ALL, "");
+
+	int follow = 0;
+	int type = LINES;
+	intmax_t count = -10;
+
+	int c;
+	char *end;
+	while ((c = getopt(argc, argv, "c:fn:")) != -1) {
+		switch (c) {
+		case 'c':
+		case 'n':
+			type = (c == 'c') ? BYTES : LINES;
+			count = -(imaxabs(strtoimax(optarg, &end, 10)) - 1);
+			if (*end != '\0') {
+				fprintf(stderr, "tail: invalid count %s\n", optarg);
+				return 1;
+			}
+			if (optarg[0] == '+') {
+				count = -count;
+			}
+			break;
+
+		case 'f':
+			follow = 1;
+			break;
+
+		default:
+			return 1;
+		}
+	}
+
+	return tail(argv[optind], follow, type, count);
+}