tail: -50 text bytes

diff --git a/coreutils/tail.c b/coreutils/tail.c
index b690b370ede35d8959d8d578b7eec039bf9f39ab..a753a10b799c95a39b6958ae79ffffb6aad510c4 100644 (file)
--- a/coreutils/tail.c
+++ b/coreutils/tail.c
@@ -29,44 +29,30 @@
 static const struct suffix_mult tail_suffixes[] = {
        { "b", 512 },
        { "k", 1024 },
-       { "m", 1048576 },
+       { "m", 1024*1024 },
        { NULL, 0 }
 };
 
 static int status;
 
-static void tail_xbb_full_write(const char *buf, size_t len)
-{
-       /* If we get a write error, there is really no sense in continuing. */
-       if (full_write(STDOUT_FILENO, buf, len) < 0)
-               bb_perror_nomsg_and_die();
-}
-
 static void tail_xprint_header(const char *fmt, const char *filename)
 {
-#if defined __GLIBC__
-       if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
+       if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
                bb_perror_nomsg_and_die();
-       }
-#else
-       int hdr_len = strlen(fmt) + strlen(filename);
-       char *hdr = xzalloc(hdr_len);
-       sprintf(hdr, filename, filename);
-       tail_xbb_full_write(hdr, hdr_len);
-#endif
 }
 
 static ssize_t tail_read(int fd, char *buf, size_t count)
 {
        ssize_t r;
-       off_t current,end;
+       off_t current, end;
        struct stat sbuf;
 
        end = current = lseek(fd, 0, SEEK_CUR);
        if (!fstat(fd, &sbuf))
                end = sbuf.st_size;
        lseek(fd, end < current ? 0 : current, SEEK_SET);
-       if ((r = safe_read(fd, buf, count)) < 0) {
+       r = safe_read(fd, buf, count);
+       if (r < 0) {
                bb_perror_msg(bb_msg_read_error);
                status = EXIT_FAILURE;
        }
@@ -74,82 +60,55 @@ static ssize_t tail_read(int fd, char *buf, size_t count)
        return r;
 }
 
-static const char tail_opts[] =
-       "fn:c:"
-#if ENABLE_FEATURE_FANCY_TAIL
-       "qs:v"
-#endif
-       ;
-
 static const char header_fmt[] = "\n==> %s <==\n";
 
 int tail_main(int argc, char **argv)
 {
-       long count = 10;
+       unsigned count = 10;
        unsigned sleep_period = 1;
        int from_top = 0;
-       int follow = 0;
        int header_threshhold = 1;
-       int count_bytes = 0;
+       const char *str_c, *str_n, *str_s;
 
        char *tailbuf;
        size_t tailbufsize;
        int taillen = 0;
        int newline = 0;
+       int nfiles, nread, nwrite, seen, i, opt;
 
-       int *fds, nfiles, nread, nwrite, seen, i, opt;
+       int *fds;
        char *s, *buf;
        const char *fmt;
 
+       void eat_num(const char *p) {
+               if (*p == '-') p++;
+               else if (*p == '+') { p++; from_top = 1; }
+               count = xatou_sfx(p, tail_suffixes);
+       }
+
+
 #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
        /* Allow legacy syntax of an initial numeric option without -n. */
        if (argc >= 2 && (argv[1][0] == '+' || argv[1][0] == '-')
         && isdigit(argv[1][1])
        ) {
-               optind = 2;
-               optarg = argv[1];
-               goto GET_COUNT;
+               argv[0] = "-n";
+               argv--;
+               argc++;
        }
 #endif
 
-       while ((opt = getopt(argc, argv, tail_opts)) > 0) {
-               switch (opt) {
-                       case 'f':
-                               follow = 1;
-                               break;
-                       case 'c':
-                               count_bytes = 1;
-                               /* FALLS THROUGH */
-                       case 'n':
-#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
- GET_COUNT:
-#endif
-                               from_top = 0;
-                               if (*optarg == '+') {
-                                       ++optarg;
-                                       from_top = 1;
-                               }
-                               count = xatol_sfx(optarg, tail_suffixes);
-                               /* Note: Leading whitespace is an error trapped above. */
-                               if (count < 0) {
-                                       count = -count;
-                               }
-                               break;
+       opt = getopt32(argc, argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"), &str_c, &str_n, &str_s);
+#define FOLLOW (opt & 0x1)
+#define COUNT_BYTES (opt & 0x2)
+       //if (opt & 0x1) // -f
+       if (opt & 0x2) eat_num(str_c); // -c
+       if (opt & 0x4) eat_num(str_n); // -n
 #if ENABLE_FEATURE_FANCY_TAIL
-                       case 'q':
-                               header_threshhold = INT_MAX;
-                               break;
-                       case 's':
-                               sleep_period = xatou(optarg);
-                               break;
-                       case 'v':
-                               header_threshhold = 0;
-                               break;
+       if (opt & 0x8) header_threshhold = INT_MAX; // -q
+       if (opt & 0x10) sleep_period = xatou(str_s); // -s
+       if (opt & 0x20) header_threshhold = 0; // -v
 #endif
-                       default:
-                               bb_show_usage();
-               }
-       }
        argc -= optind;
        argv += optind;
 
@@ -160,34 +119,35 @@ int tail_main(int argc, char **argv)
                struct stat statbuf;
 
                if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
-                       follow = 0;
+                       opt &= ~1; /* clear FOLLOW */
                }
                *argv = (char *) bb_msg_standard_input;
                goto DO_STDIN;
        }
 
        do {
-               if (LONE_DASH(argv[i])) {
- DO_STDIN:
+               if (NOT_LONE_DASH(argv[i])) {
+                       fds[nfiles] = open(argv[i], O_RDONLY);
+                       if (fds[nfiles] < 0) {
+                               bb_perror_msg("%s", argv[i]);
+                               status = EXIT_FAILURE;
+                               continue;
+                       }
+               } else {
+ DO_STDIN:             /* "-" */
                        fds[nfiles] = STDIN_FILENO;
-               } else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
-                       bb_perror_msg("%s", argv[i]);
-                       status = EXIT_FAILURE;
-                       continue;
                }
                argv[nfiles] = argv[i];
                ++nfiles;
        } while (++i < argc);
 
-       if (!nfiles) {
+       if (!nfiles)
                bb_error_msg_and_die("no files");
-       }
 
        tailbufsize = BUFSIZ;
 
        /* tail the files */
-       if (from_top < count_bytes) {   /* Each is 0 or 1, so true iff 0 < 1. */
-               /* Hence, !from_top && count_bytes */
+       if (!from_top && COUNT_BYTES) {
                if (tailbufsize < count) {
                        tailbufsize = count + BUFSIZ;
                }
@@ -203,7 +163,7 @@ int tail_main(int argc, char **argv)
                 * starting file position may not be the beginning of the file.
                 * Beware of backing up too far.  See example in wc.c.
                 */
-               if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
+               if (!(count|from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
                        continue;
                }
 
@@ -221,22 +181,22 @@ int tail_main(int argc, char **argv)
                        if (from_top) {
                                nwrite = nread;
                                if (seen < count) {
-                                       if (count_bytes) {
+                                       if (COUNT_BYTES) {
                                                nwrite -= (count - seen);
                                                seen = count;
                                        } else {
                                                s = buf;
                                                do {
                                                        --nwrite;
-                                                       if ((*s++ == '\n') && (++seen == count)) {
+                                                       if (*s++ == '\n' && ++seen == count) {
                                                                break;
                                                        }
                                                } while (nwrite);
                                        }
                                }
-                               tail_xbb_full_write(buf + nread - nwrite, nwrite);
+                               xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
                        } else if (count) {
-                               if (count_bytes) {
+                               if (COUNT_BYTES) {
                                        taillen += nread;
                                        if (taillen > count) {
                                                memmove(tailbuf, tailbuf + taillen - count, count);
@@ -286,7 +246,7 @@ int tail_main(int argc, char **argv)
                }
 
                if (!from_top) {
-                       tail_xbb_full_write(tailbuf, taillen);
+                       xwrite(STDOUT_FILENO, tailbuf, taillen);
                }
 
                taillen = 0;
@@ -296,7 +256,7 @@ int tail_main(int argc, char **argv)
 
        fmt = NULL;
 
-       while (follow) {
+       if (FOLLOW) while (1) {
                sleep(sleep_period);
                i = 0;
                do {
@@ -308,7 +268,7 @@ int tail_main(int argc, char **argv)
                                        tail_xprint_header(fmt, argv[i]);
                                        fmt = NULL;
                                }
-                               tail_xbb_full_write(buf, nread);
+                               xwrite(STDOUT_FILENO, buf, nread);
                        }
                } while (++i < nfiles);
        }