From 135b557f6d14c3ce4d60419602d8ca92316f9a71 Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@xenon.localdomain>
Date: Mon, 13 Mar 2006 18:16:41 +0100
Subject: Initial import

---
 simpletail.c | 178 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 178 insertions(+)
 create mode 100644 simpletail.c

(limited to 'simpletail.c')

diff --git a/simpletail.c b/simpletail.c
new file mode 100644
index 0000000..b5df235
--- /dev/null
+++ b/simpletail.c
@@ -0,0 +1,178 @@
+/*
+ * simpletail.c
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+
+#include "inotify.h"
+#include "inotify-syscalls.h"
+
+#include "inotail.h"
+
+#define BUFFER_SIZE 4096
+
+off_t lines(int fd, int file_size, unsigned int nr_lines)
+{
+	int i;
+	char buf[BUFFER_SIZE];
+	off_t offset = file_size;
+
+	/* Negative offsets don't make sense here */
+	if (offset < 0)
+		offset = 0;
+
+	while (offset > 0 && nr_lines > 0) {
+		int rc;
+		int block_size = BUFFER_SIZE; /* Size of the current block we're reading */
+
+		if (offset < BUFFER_SIZE)
+			block_size = offset;
+
+		/* Start of current block */
+		offset -= block_size;
+
+		dprintf("  offset: %lu\n", offset);
+
+		lseek(fd, offset, SEEK_SET);
+
+		rc = read(fd, &buf, block_size);
+
+		for (i = block_size; i > 0; i--) {
+			if (buf[i] == '\n') {
+				dprintf("  Found \\n at position %d\n", i);
+				nr_lines--;
+
+				if (nr_lines == 0)
+					break;
+			}
+		}
+	}
+
+	if (nr_lines == 0)
+		offset += i + 1; /* We don't want the first \n */
+
+	return offset;
+}
+
+int watch_file(const char *filename, off_t offset)
+{
+	int ifd, watch;
+	struct inotify_event *inev;
+	char buf[BUFFER_SIZE];
+
+	dprintf(">> Watching %s\n", filename);
+
+	ifd = inotify_init();
+	if (ifd < 0) {
+		perror("inotify_init()");
+		exit(-2);
+	}
+
+	watch = inotify_add_watch(ifd, filename, IN_MODIFY|IN_DELETE_SELF|IN_MOVE_SELF|IN_UNMOUNT);
+
+	memset(&buf, 0, sizeof(buf));
+
+	while (1) {
+		int len;
+
+		len = read(ifd, buf, sizeof(buf));
+		inev = (struct inotify_event *) &buf;
+
+		while (len > 0) {
+			if (inev->mask & IN_MODIFY) {
+				int ffd, block_size;
+				char fbuf[BUFFER_SIZE];
+				struct stat finfo;
+
+				dprintf("  File '%s' modified.\n", filename);
+				dprintf("  offset: %lu.\n", offset);
+
+				ffd = open(filename, O_RDONLY);
+				if (fstat(ffd, &finfo) < 0) {
+					perror("fstat()");
+					return -1;
+				}
+
+				/* XXX: block_size could be bigger than BUFFER_SIZE */
+				block_size = finfo.st_size - offset;
+				if (block_size < 0)
+					block_size = 0;
+
+				lseek(ffd, offset, SEEK_SET);
+				while (read(ffd, &fbuf, BUFFER_SIZE) != 0) {
+					write(STDOUT_FILENO, fbuf, block_size);
+				}
+
+				offset = finfo.st_size;
+
+				close(ffd);
+			}
+
+			if (inev->mask & IN_DELETE_SELF) {
+				dprintf("  File '%s' deleted.\n", filename);
+				return -1;
+			}
+			if (inev->mask & IN_MOVE_SELF) {
+				dprintf("  File '%s' moved.\n", filename);
+				return -1;
+			}
+			if (inev->mask & IN_UNMOUNT) {
+				dprintf("  Device containing file '%s' unmounted.\n", filename);
+				return -1;
+			}
+
+			len -= sizeof(struct inotify_event) + inev->len;
+			inev = (struct inotify_event *) ((char *) inev + sizeof(struct inotify_event) + inev->len);
+		}
+	}
+}
+
+int main(int argc, char **argv)
+{
+	int fd;
+	int nr_lines = 0;
+	int ret = 0;
+	struct stat finfo;
+	char buf[BUFFER_SIZE];
+	off_t offset = 0;
+
+	if (argc < 3) {
+		fprintf(stderr, "%s <nr-lines> <file> <forever?>\n", argv[0]);
+		return -1;
+	}
+
+	nr_lines = strtol(argv[1], NULL, 0) + 1;
+	fd = open(argv[2], O_RDONLY);
+
+	if (fd < 0) {
+		perror("open()");
+		return -1;
+	}
+
+	if (fstat(fd, &finfo) < 0) {
+		perror("fstat()");
+		return -1;
+	}
+
+	offset = lines(fd, finfo.st_size, nr_lines);
+	dprintf("  offset: %lu.\n", offset);
+
+	lseek(fd, offset, SEEK_SET);
+	while (read(fd, &buf, BUFFER_SIZE) != 0) {
+		write(STDOUT_FILENO, buf, finfo.st_size - offset);
+	}
+
+	close(fd);
+
+	if (argv[3])
+		ret = watch_file(argv[2], finfo.st_size);
+
+	return ret;
+}
-- 
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