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-rw-r--r--toys/posix/tail.c348
1 files changed, 173 insertions, 175 deletions
diff --git a/toys/posix/tail.c b/toys/posix/tail.c
index d0711c0c..bdbbfb30 100644
--- a/toys/posix/tail.c
+++ b/toys/posix/tail.c
@@ -1,6 +1,4 @@
-/* vi: set sw=4 ts=4:
- *
- * tail.c - copy last lines from input to stdout.
+/* tail.c - copy last lines from input to stdout.
*
* Copyright 2012 Timothy Elliott <tle@holymonkey.com>
*
@@ -9,62 +7,62 @@
USE_TAIL(NEWTOY(tail, "fc-n-", TOYFLAG_BIN))
config TAIL
- bool "tail"
- default y
- help
- usage: tail [-n|c number] [-f] [file...]
+ bool "tail"
+ default y
+ help
+ 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.
+ 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 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
config TAIL_SEEK
- bool "tail seek support"
- default y
- depends on TAIL
- help
- This version uses lseek, which is faster on large files.
+ bool "tail seek support"
+ default y
+ depends on TAIL
+ help
+ This version uses lseek, which is faster on large files.
*/
#define FOR_tail
#include "toys.h"
GLOBALS(
- long lines;
- long bytes;
+ long lines;
+ long bytes;
- int file_no;
+ int file_no;
)
struct line_list {
- struct line_list *next, *prev;
- char *data;
- int len;
+ struct line_list *next, *prev;
+ char *data;
+ int len;
};
static struct line_list *get_chunk(int fd, int len)
{
- struct line_list *line = xmalloc(sizeof(struct line_list)+len);
+ struct line_list *line = xmalloc(sizeof(struct line_list)+len);
- line->data = ((char *)line) + sizeof(struct line_list);
- line->len = readall(fd, line->data, len);
+ line->data = ((char *)line) + sizeof(struct line_list);
+ line->len = readall(fd, line->data, len);
- if (line->len < 1) {
- free(line);
- return 0;
- }
+ if (line->len < 1) {
+ free(line);
+ return 0;
+ }
- return line;
+ return line;
}
static void dump_chunk(void *ptr)
{
- struct line_list *list = ptr;
- xwrite(1, list->data, list->len);
- free(list);
+ struct line_list *list = ptr;
+ xwrite(1, list->data, list->len);
+ free(list);
}
// Reading through very large files is slow. Using lseek can speed things
@@ -72,156 +70,156 @@ static void dump_chunk(void *ptr)
// Note: bytes and lines are negative here.
static int try_lseek(int fd, long bytes, long lines)
{
- struct line_list *list = 0, *temp;
- 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<0) return 0;
-
- // Seek to the right spot, output data from there.
- if (bytes) {
- if (lseek(fd, bytes, SEEK_END)<0) lseek(fd, 0, SEEK_SET);
- xsendfile(fd, 1);
- return 1;
- }
-
- // Read from end to find enough lines, then output them.
-
- bytes = pos;
- while (lines && pos) {
- int offset;
-
- // Read in next chunk from end of file
- 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) list->next = temp;
- list = temp;
-
- // Count newlines in this chunk.
- offset = list->len;
- while (offset--) {
- // If the last line ends with a newline, that one doesn't count.
- if (!flag) {
- flag++;
-
- continue;
- }
-
- // Start outputting data right after newline
- if (list->data[offset] == '\n' && !++lines) {
- offset++;
- list->data += offset;
- list->len -= offset;
-
- break;
- }
- }
- }
-
- // Output stored data
- llist_traverse(list, dump_chunk);
-
- // In case of -f
- lseek(fd, bytes, SEEK_SET);
- return 1;
+ struct line_list *list = 0, *temp;
+ 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<0) return 0;
+
+ // Seek to the right spot, output data from there.
+ if (bytes) {
+ if (lseek(fd, bytes, SEEK_END)<0) lseek(fd, 0, SEEK_SET);
+ xsendfile(fd, 1);
+ return 1;
+ }
+
+ // Read from end to find enough lines, then output them.
+
+ bytes = pos;
+ while (lines && pos) {
+ int offset;
+
+ // Read in next chunk from end of file
+ 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) list->next = temp;
+ list = temp;
+
+ // Count newlines in this chunk.
+ offset = list->len;
+ while (offset--) {
+ // If the last line ends with a newline, that one doesn't count.
+ if (!flag) {
+ flag++;
+
+ continue;
+ }
+
+ // Start outputting data right after newline
+ if (list->data[offset] == '\n' && !++lines) {
+ offset++;
+ list->data += offset;
+ list->len -= offset;
+
+ break;
+ }
+ }
+ }
+
+ // Output stored data
+ llist_traverse(list, dump_chunk);
+
+ // In case of -f
+ lseek(fd, bytes, SEEK_SET);
+ return 1;
}
// Called for each file listed on command line, and/or stdin
static void do_tail(int fd, char *name)
{
- long bytes = TT.bytes, lines = TT.lines;
-
- if (toys.optc > 1) {
- if (TT.file_no++) xputc('\n');
- xprintf("==> %s <==\n", name);
- }
-
- // Are we measuring from the end of the file?
-
- if (bytes<0 || lines<0) {
- struct line_list *list = 0, *new;
-
- // The slow codepath is always needed, and can handle all input,
- // so make lseek support optional.
- if (CFG_TAIL_SEEK && try_lseek(fd, bytes, lines));
-
- // Read data until we run out, keep a trailing buffer
- else for (;;) {
- int len, count;
- char *try;
-
- if (!(new = get_chunk(fd, sizeof(toybuf)))) break;
- // append in order
- dlist_add_nomalloc((struct double_list **)&list,
- (struct double_list *)new);
-
- // Measure new chunk, discarding extra data from buffer
- len = new->len;
- try = new->data;
- for (count=0; count<len; count++) {
- if ((toys.optflags & FLAG_c) && bytes) {
- bytes++;
- continue;
- }
-
- if (lines) {
- if(try[count] != '\n' && count != len-1) continue;
- if (lines<0) {
- if (!++lines) ++lines;
- continue;
- }
- }
-
- // Time to discard data; given that bytes and lines were
- // nonzero coming in, we can't discard too much if we're
- // measuring right.
- do {
- char c = *(list->data++);
- if (!(--list->len)) {
- struct line_list *next = list->next;
- list->prev->next = next;
- list->next->prev = list->prev;
- free(list);
- list = next;
- }
- if (c == '\n') break;
- } while (lines);
- }
- }
-
- // Output/free the buffer.
- llist_traverse(list, dump_chunk);
-
- // Measuring from the beginning of the file.
- } else for (;;) {
- int len, offset = 0;
-
- // Error while reading does not exit. Error writing does.
- len = read(fd, toybuf, sizeof(toybuf));
- if (len<1) break;
- while (bytes > 1 || lines > 1) {
- bytes--;
- if (toybuf[offset++] == '\n') lines--;
- if (offset >= len) break;
- }
- if (offset<len) xwrite(1, toybuf+offset, len-offset);
- }
-
- // -f support: cache name/descriptor
+ long bytes = TT.bytes, lines = TT.lines;
+
+ if (toys.optc > 1) {
+ if (TT.file_no++) xputc('\n');
+ xprintf("==> %s <==\n", name);
+ }
+
+ // Are we measuring from the end of the file?
+
+ if (bytes<0 || lines<0) {
+ struct line_list *list = 0, *new;
+
+ // The slow codepath is always needed, and can handle all input,
+ // so make lseek support optional.
+ if (CFG_TAIL_SEEK && try_lseek(fd, bytes, lines));
+
+ // Read data until we run out, keep a trailing buffer
+ else for (;;) {
+ int len, count;
+ char *try;
+
+ if (!(new = get_chunk(fd, sizeof(toybuf)))) break;
+ // append in order
+ dlist_add_nomalloc((struct double_list **)&list,
+ (struct double_list *)new);
+
+ // Measure new chunk, discarding extra data from buffer
+ len = new->len;
+ try = new->data;
+ for (count=0; count<len; count++) {
+ if ((toys.optflags & FLAG_c) && bytes) {
+ bytes++;
+ continue;
+ }
+
+ if (lines) {
+ if(try[count] != '\n' && count != len-1) continue;
+ if (lines<0) {
+ if (!++lines) ++lines;
+ continue;
+ }
+ }
+
+ // Time to discard data; given that bytes and lines were
+ // nonzero coming in, we can't discard too much if we're
+ // measuring right.
+ do {
+ char c = *(list->data++);
+ if (!(--list->len)) {
+ struct line_list *next = list->next;
+ list->prev->next = next;
+ list->next->prev = list->prev;
+ free(list);
+ list = next;
+ }
+ if (c == '\n') break;
+ } while (lines);
+ }
+ }
+
+ // Output/free the buffer.
+ llist_traverse(list, dump_chunk);
+
+ // Measuring from the beginning of the file.
+ } else for (;;) {
+ int len, offset = 0;
+
+ // Error while reading does not exit. Error writing does.
+ len = read(fd, toybuf, sizeof(toybuf));
+ if (len<1) break;
+ while (bytes > 1 || lines > 1) {
+ bytes--;
+ if (toybuf[offset++] == '\n') lines--;
+ if (offset >= len) break;
+ }
+ if (offset<len) xwrite(1, toybuf+offset, len-offset);
+ }
+
+ // -f support: cache name/descriptor
}
void tail_main(void)
{
- // if nothing specified, default -n to -10
- if (!(toys.optflags&(FLAG_n|FLAG_c))) TT.lines = -10;
+ // if nothing specified, default -n to -10
+ if (!(toys.optflags&(FLAG_n|FLAG_c))) TT.lines = -10;
- loopfiles(toys.optargs, do_tail);
+ loopfiles(toys.optargs, do_tail);
- // do -f stuff
+ // do -f stuff
}
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