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-rw-r--r--toys/posix/tail.c106
1 files changed, 52 insertions, 54 deletions
diff --git a/toys/posix/tail.c b/toys/posix/tail.c
index bea8bf5c..e1048be7 100644
--- a/toys/posix/tail.c
+++ b/toys/posix/tail.c
@@ -4,20 +4,20 @@
*
* See http://opengroup.org/onlinepubs/9699919799/utilities/tail.html
-USE_TAIL(NEWTOY(tail, "fc-n-", TOYFLAG_BIN))
+USE_TAIL(NEWTOY(tail, "fc-n-[-cn]", TOYFLAG_BIN))
config TAIL
bool "tail"
default y
help
- usage: tail [-n|c number] [-f] [file...]
+ usage: tail [-n|c NUMBER] [-f] [FILE...]
Copy last lines from files to stdout. If no files listed, copy from
stdin. Filename "-" is a synonym for stdin.
- -n output the last X lines (default 10), +X counts from start.
- -c output the last X bytes, +X counts from start
- -f follow file, waiting for more data to be appended
+ -n output the last NUMBER lines (default 10), +X counts from start.
+ -c output the last NUMBER bytes, +NUMBER counts from start
+ -f follow FILE(s), waiting for more data to be appended
config TAIL_SEEK
bool "tail seek support"
@@ -38,20 +38,20 @@ GLOBALS(
)
struct line_list {
- struct line_list *next;
+ struct line_list *next, *prev;
char *data;
- size_t len;
+ int len;
};
-static struct line_list *get_chunk(int fd, size_t len)
+static struct line_list *get_chunk(int fd, int len)
{
struct line_list *line = xmalloc(sizeof(struct line_list)+len);
- line->data = (char*)line + sizeof(struct line_list);
+ memset(line, 0, sizeof(struct line_list));
+ line->data = ((char *)line) + sizeof(struct line_list);
line->len = readall(fd, line->data, len);
- line->next = 0;
- if (line->len + 1 < 2) {
+ if (line->len < 1) {
free(line);
return 0;
}
@@ -62,9 +62,8 @@ static struct line_list *get_chunk(int fd, size_t len)
static void dump_chunk(void *ptr)
{
struct line_list *list = ptr;
- size_t len = list->len - (list->data - (char*)list - sizeof(struct line_list));
- xwrite(1, list->data, len);
+ xwrite(1, list->data, list->len);
free(list);
}
@@ -74,11 +73,11 @@ static void dump_chunk(void *ptr)
static int try_lseek(int fd, long bytes, long lines)
{
struct line_list *list = 0, *temp;
- int flag = 0;
- size_t chunk = sizeof(toybuf), pos = lseek(fd, 0, SEEK_END);
+ int flag = 0, chunk = sizeof(toybuf);
+ ssize_t pos = lseek(fd, 0, SEEK_END);
// If lseek() doesn't work on this stream, return now.
- if (pos == -1) return 0;
+ if (pos<0) return 0;
// Seek to the right spot, output data from there.
if (bytes) {
@@ -91,17 +90,17 @@ static int try_lseek(int fd, long bytes, long lines)
bytes = pos;
while (lines && pos) {
- size_t offset;
+ int offset;
// Read in next chunk from end of file
- if (chunk > pos) chunk = pos;
+ if (chunk>pos) chunk = pos;
pos -= chunk;
if (pos != lseek(fd, pos, SEEK_SET)) {
perror_msg("seek failed");
break;
}
if (!(temp = get_chunk(fd, chunk))) break;
- if (list) temp->next = list;
+ temp->next = list;
list = temp;
// Count newlines in this chunk.
@@ -114,13 +113,13 @@ static int try_lseek(int fd, long bytes, long lines)
else if (list->data[offset] == '\n' && !++lines) {
offset++;
list->data += offset;
+ list->len -= offset;
- goto done;
+ break;
}
}
}
-done:
// Output stored data
llist_traverse(list, dump_chunk);
@@ -133,6 +132,7 @@ done:
static void do_tail(int fd, char *name)
{
long bytes = TT.bytes, lines = TT.lines;
+ int linepop = 1;
if (toys.optc > 1) {
if (TT.file_no++) xputc('\n');
@@ -142,14 +142,7 @@ static void do_tail(int fd, char *name)
// Are we measuring from the end of the file?
if (bytes<0 || lines<0) {
- struct line_list *head = 0, *tail, *new;
- // circular buffer of lines
- struct {
- char *start;
- struct line_list *inchunk;
- } *l = xzalloc(2*-lines*sizeof(void*));
- int i = 0, flag = 0;
- size_t count, len = bytes;
+ struct line_list *list = 0, *new;
// The slow codepath is always needed, and can handle all input,
// so make lseek support optional.
@@ -157,39 +150,44 @@ static void do_tail(int fd, char *name)
// Read data until we run out, keep a trailing buffer
for (;;) {
- char *try;
-
+ // Read next page of data, appending to linked list in order
if (!(new = get_chunk(fd, sizeof(toybuf)))) break;
- // append in order
- if (head) tail->next = new;
- else head = new;
- tail = new;
-
- try = new->data;
- if (lines) for (count = 0; count < new->len; count++, try++) {
- if (flag) { // last char was a newline
- while (l[i].inchunk && (l[i].inchunk!=head)) free(llist_pop(&head));
- l[i].inchunk = tail;
- l[i].start = try;
- i = (i + 1) % -lines;
- flag = 0;
+ dlist_add_nomalloc((void *)&list, (void *)new);
+
+ // If tracing bytes, add until we have enough, discarding overflow.
+ if (TT.bytes) {
+ bytes += new->len;
+ if (bytes > 0) {
+ while (list->len <= bytes) {
+ bytes -= list->len;
+ free(dlist_pop(&list));
+ }
+ list->data += bytes;
+ list->len -= bytes;
}
- if (*try == '\n') flag = 1;
- } else { // bytes
- if (len + new->len < len) flag = 1; // overflow -> have now read enough
- for (len += new->len; flag && (len - head->len < len);) {
- len -= head->len;
- free(llist_pop(&head));
+ } else {
+ int len = new->len, count;
+ char *try = new->data;
+
+ // First character _after_ a newline starts a new line, which
+ // works even if file doesn't end with a newline
+ for (count=0; count<len; count++) {
+ if (linepop) lines++;
+ linepop = try[count] == '\n';
+
+ if (lines > 0) {
+ do {
+ if (!--(list->len)) free(dlist_pop(&list));
+ } while (*(list->data++) != '\n');
+ lines--;
+ }
}
}
}
- if (lines) head->data = l[i].start;
- else head->data += len;
// Output/free the buffer.
- llist_traverse(head, dump_chunk);
+ llist_traverse(list, dump_chunk);
- free(l);
// Measuring from the beginning of the file.
} else for (;;) {
int len, offset = 0;