diff options
Diffstat (limited to 'mlog.c')
| -rw-r--r-- | mlog.c | 56 |
1 files changed, 54 insertions, 2 deletions
diff --git a/mlog.c b/mlog.c index 4167555..b5c06b7 100644 --- a/mlog.c +++ b/mlog.c @@ -21,6 +21,7 @@ int ifd; int uflag; /* remove duplicates */ int fflag; /* -f follow / -ff tail+follow */ int sflag; /* strip socklog prefix */ +int nflag; /* number of lines at end to print */ struct logfile { char *path; @@ -262,19 +263,68 @@ nextline(int i) return 0; } +void +tail_line(FILE *file, int n) +{ + size_t page = 4096; + + if (fseek(file, -page, SEEK_END) < 0) { + if (errno == EINVAL) + rewind(file); + else + return; /* can't seek */ + } + + int l = -1; /* line ends with newline */ + char buf[page]; + + while (1) { + clearerr(file); + long off = ftell(file); + ssize_t in = fread(buf, 1, page, file); + + size_t i; + for (i = in; l < n && i > 0; i--) { + if (buf[i] == '\n') + l++; + } + + if (l == n) { + fseek(file, off + i + 2, SEEK_SET); + break; + } else if (off == 0) { /* file too short */ + rewind(file); + break; + } + + /* seek back more and count again */ + if (fseek(file, -2*page, SEEK_CUR) < 0) { + if (errno == EINVAL) { + rewind(file); + break; + } else { + return; + } + } + } + + clearerr(file); +} + int main(int argc, char *argv[]) { int opt; - while ((opt = getopt(argc, argv, "fsu")) != -1) { + while ((opt = getopt(argc, argv, "fn:su")) != -1) { switch (opt) { case 'f': fflag++; break; + case 'n': nflag = atoi(optarg); break; case 's': sflag++; break; case 'u': uflag++; break; default: usage: - fputs("usage: mlog [-fsu] FILES...\n", stderr); + fputs("usage: mlog [-fsu] [-n LINES] FILES...\n", stderr); exit(2); } } @@ -301,6 +351,8 @@ main(int argc, char *argv[]) strerror(errno)); if (fflag > 1 && logs[i].file) fseek(logs[i].file, 0L, SEEK_END); + else if (nflag > 0 && logs[i].file) + tail_line(logs[i].file, nflag); } while (1) { |