diff options
Diffstat (limited to 'toys/posix/tail.c')
| -rw-r--r-- | toys/posix/tail.c | 106 |
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; |