When last lines happen to be greater than string buffer size for fgets()
the number of printed lines resulted to too few.
Signed-off-by: Sami Kerola <kerolasa@xxxxxx>
---
text-utils/tailf.c | 56 +++++++++++++++++++++++++-----------------------------
1 file changed, 26 insertions(+), 30 deletions(-)
diff --git a/text-utils/tailf.c b/text-utils/tailf.c
index 0c477ad..b5ea4c2 100644
--- a/text-utils/tailf.c
+++ b/text-utils/tailf.c
@@ -36,6 +36,8 @@
#include <ctype.h>
#include <errno.h>
#include <getopt.h>
+#include <sys/mman.h>
+
#ifdef HAVE_INOTIFY_INIT
#include <sys/inotify.h>
#endif
@@ -49,40 +51,34 @@
#define DEFAULT_LINES 10
static void
-tailf(const char *filename, int lines)
+tailf(const char *filename, unsigned long lines, struct stat *old)
{
- char *buf, *p;
- int head = 0;
- int tail = 0;
- FILE *str;
- int i;
+ int fd;
+ size_t i;
+ char *data;
- if (!(str = fopen(filename, "r")))
+ if (!(fd = open(filename, O_RDONLY)))
err(EXIT_FAILURE, _("cannot open %s"), filename);
-
- buf = xmalloc((lines ? lines : 1) * BUFSIZ);
- p = buf;
- while (fgets(p, BUFSIZ, str)) {
- if (++tail >= lines) {
- tail = 0;
- head = 1;
+ data = mmap(0, old->st_size, PROT_READ, MAP_SHARED, fd, 0);
+ i = (size_t)old->st_size - 1;
+ /* humans do not think last new line in a file should be counted,
+ * in that case do off by one from counter point of view */
+ if (data[i] == '\n')
+ lines++;
+ while (i) {
+ if (data[i] == '\n') {
+ if (--lines == 0) {
+ i++;
+ break;
+ }
}
- p = buf + (tail * BUFSIZ);
+ i--;
}
-
- if (head) {
- for (i = tail; i < lines; i++)
- fputs(buf + (i * BUFSIZ), stdout);
- for (i = 0; i < tail; i++)
- fputs(buf + (i * BUFSIZ), stdout);
- } else {
- for (i = head; i < tail; i++)
- fputs(buf + (i * BUFSIZ), stdout);
- }
-
+ while (i < (size_t)old->st_size)
+ putchar(data[i++]);
+ munmap(data, old->st_size);
+ close(fd);
fflush(stdout);
- free(buf);
- fclose(str);
}
static void
@@ -283,8 +279,8 @@ int main(int argc, char **argv)
if (stat(filename, &old) != 0)
err(EXIT_FAILURE, _("stat of %s failed"), filename);
-
- tailf(filename, lines);
+ if (lines && old.st_size)
+ tailf(filename, lines, &old);
#ifdef HAVE_INOTIFY_INIT
if (!watch_file_inotify(filename, &old))
--
2.3.0
--
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