f193aeac1
Denys Vlasenko
2021-06-02
Subject
tail: do not lose the tail of old file if new file (-F) is detected
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Commit Diff GitHub →
coreutils/tail.c+26 -12
| @@ -346,9 +346,11 @@ int tail_main(int argc, char **argv) | |
| int nread; | |
| const char *filename = argv[i]; | |
| int fd = fds[i]; | |
| + | int new_fd = -1; |
| + | struct stat sbuf; |
| if (FOLLOW_RETRY) { | |
| - | struct stat sbuf, fsbuf; |
| + | struct stat fsbuf; |
| if (fd < 0 | |
| || fstat(fd, &fsbuf) < 0 | |
| @@ -356,19 +358,21 @@ int tail_main(int argc, char **argv) | |
| || fsbuf.st_dev != sbuf.st_dev | |
| || fsbuf.st_ino != sbuf.st_ino | |
| ) { | |
| - | int new_fd; |
| - | |
| - | if (fd >= 0) |
| - | close(fd); |
| + | /* Looks like file has been created/renamed/deleted */ |
| new_fd = open(filename, O_RDONLY); | |
| if (new_fd >= 0) { | |
| bb_error_msg("%s has %s; following end of new file", | |
| filename, (fd < 0) ? "appeared" : "been replaced" | |
| ); | |
| + | if (fd < 0) { |
| + | /* No previously open fd for this file, |
| + | * start using new_fd immediately. */ |
| + | fds[i] = fd = new_fd; |
| + | new_fd = -1; |
| + | } |
| } else if (fd >= 0) { | |
| - | bb_perror_msg("%s has become inaccessible", filename); |
| + | bb_perror_msg("%s has been renamed or deleted", filename); |
| } | |
| - | fds[i] = fd = new_fd; |
| } | |
| } | |
| if (ENABLE_FEATURE_FANCY_TAIL && fd < 0) | |
| @@ -378,17 +382,27 @@ int tail_main(int argc, char **argv) | |
| } | |
| for (;;) { | |
| /* tail -f keeps following files even if they are truncated */ | |
| - | struct stat sbuf; |
| /* /proc files report zero st_size, don't lseek them */ | |
| - | if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) { |
| + | if (fstat(fd, &sbuf) == 0 |
| + | /* && S_ISREG(sbuf.st_mode) TODO? */ |
| + | && sbuf.st_size > 0 |
| + | ) { |
| off_t current = lseek(fd, 0, SEEK_CUR); | |
| - | if (sbuf.st_size < current) |
| + | if (sbuf.st_size < current) { |
| + | //bb_perror_msg("%s: file truncated", filename); - says coreutils 8.32 |
| xlseek(fd, 0, SEEK_SET); | |
| + | } |
| } | |
| nread = tail_read(fd, tailbuf, BUFSIZ); | |
| - | if (nread <= 0) |
| - | break; |
| + | if (nread <= 0) { |
| + | if (new_fd < 0) |
| + | break; |
| + | /* Switch to "tail -F"ing the new file */ |
| + | xmove_fd(new_fd, fd); |
| + | new_fd = -1; |
| + | continue; |
| + | } |
| if (fmt && (fd != prev_fd)) { | |
| tail_xprint_header(fmt, filename); | |
| fmt = NULL; | |