diff options
| -rw-r--r-- | coreutils/tail.c | 49 |
1 files changed, 33 insertions, 16 deletions
diff --git a/coreutils/tail.c b/coreutils/tail.c index 5f98bff..05dadcd 100644 --- a/coreutils/tail.c +++ b/coreutils/tail.c @@ -51,10 +51,10 @@ static ssize_t tail_read(int fd, char *buf, size_t count) struct stat sbuf; /* /proc files report zero st_size, don't lseek them. */ - if (fstat(fd, &sbuf) == 0 && sbuf.st_size) { + if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) { current = lseek(fd, 0, SEEK_CUR); if (sbuf.st_size < current) - lseek(fd, 0, SEEK_SET); + xlseek(fd, 0, SEEK_SET); } r = full_read(fd, buf, count); @@ -174,8 +174,9 @@ int tail_main(int argc, char **argv) int newlines_seen; unsigned seen; int nread; + int fd = fds[i]; - if (ENABLE_FEATURE_FANCY_TAIL && fds[i] < 0) + if (ENABLE_FEATURE_FANCY_TAIL && fd < 0) continue; /* may happen with -E */ if (nfiles > header_threshhold) { @@ -183,30 +184,46 @@ int tail_main(int argc, char **argv) fmt = header_fmt; } - /* Optimizing count-bytes case if the file is seekable. - * Beware of backing up too far. - * Also we exclude files with size 0 (because of /proc/xxx) */ - if (COUNT_BYTES && !from_top) { - off_t current = lseek(fds[i], 0, SEEK_END); + if (!from_top) { + off_t current = lseek(fd, 0, SEEK_END); if (current > 0) { - if (count == 0) - continue; /* showing zero bytes is easy :) */ - current -= count; + unsigned off; + if (COUNT_BYTES) { + /* Optimizing count-bytes case if the file is seekable. + * Beware of backing up too far. + * Also we exclude files with size 0 (because of /proc/xxx) */ + if (count == 0) + continue; /* showing zero bytes is easy :) */ + current -= count; + if (current < 0) + current = 0; + xlseek(fd, current, SEEK_SET); + bb_copyfd_size(fd, STDOUT_FILENO, count); + continue; + } +#if 1 /* This is technically incorrect for *LONG* strings, but very useful */ + /* Optimizing count-lines case if the file is seekable. + * We assume the lines are <64k. + * (Users complain that tail takes too long + * on multi-gigabyte files) */ + off = (count | 0xf); /* for small counts, be more paranoid */ + if (off > (INT_MAX / (64*1024))) + off = (INT_MAX / (64*1024)); + current -= off * (64*1024); if (current < 0) current = 0; - xlseek(fds[i], current, SEEK_SET); - bb_copyfd_size(fds[i], STDOUT_FILENO, count); - continue; + xlseek(fd, current, SEEK_SET); +#endif } } buf = tailbuf; taillen = 0; /* "We saw 1st line/byte". - * Used only by +N code ("start from Nth", 1-based) */ + * Used only by +N code ("start from Nth", 1-based): */ seen = 1; newlines_seen = 0; - while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) { + while ((nread = tail_read(fd, buf, tailbufsize-taillen)) > 0) { if (from_top) { int nwrite = nread; if (seen < count) { |