6651e4260
Denys Vlasenko
2013-07-02
Subject
tail: track file size only in -f mode
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Commit Diff GitHub →
coreutils/tail.c+15 -11
| @@ -66,17 +66,21 @@ static void tail_xprint_header(const char *fmt, const char *filename) | |
| bb_perror_nomsg_and_die(); | |
| } | |
| - | static ssize_t tail_read(int fd, char *buf, size_t count) |
| + | static ssize_t tail_read(int fd, char *buf, size_t count, int follow) |
| { | |
| ssize_t r; | |
| - | off_t current; |
| - | struct stat sbuf; |
| - | |
| - | /* /proc files report zero st_size, don't lseek them. */ |
| - | if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) { |
| - | current = lseek(fd, 0, SEEK_CUR); |
| - | if (sbuf.st_size < current) |
| - | xlseek(fd, 0, SEEK_SET); |
| + | |
| + | if (follow) { |
| + | /* tail -f keeps following files even if they are truncated */ |
| + | off_t current; |
| + | struct stat sbuf; |
| + | |
| + | /* /proc files report zero st_size, don't lseek them */ |
| + | if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) { |
| + | current = lseek(fd, 0, SEEK_CUR); |
| + | if (sbuf.st_size < current) |
| + | xlseek(fd, 0, SEEK_SET); |
| + | } |
| } | |
| r = full_read(fd, buf, count); | |
| @@ -251,7 +255,7 @@ int tail_main(int argc, char **argv) | |
| * Used only by +N code ("start from Nth", 1-based): */ | |
| seen = 1; | |
| newlines_seen = 0; | |
| - | while ((nread = tail_read(fd, buf, tailbufsize - taillen)) > 0) { |
| + | while ((nread = tail_read(fd, buf, tailbufsize - taillen, /*follow:*/ 0)) > 0) { |
| if (G.from_top) { | |
| int nwrite = nread; | |
| if (seen < count) { | |
| @@ -363,7 +367,7 @@ int tail_main(int argc, char **argv) | |
| if (nfiles > header_threshhold) { | |
| fmt = header_fmt_str; | |
| } | |
| - | while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) { |
| + | while ((nread = tail_read(fd, tailbuf, BUFSIZ, /*follow:*/ 1)) > 0) { |
| if (fmt) { | |
| tail_xprint_header(fmt, filename); | |
| fmt = NULL; | |